By the Lunar and Planetary Institute

By the Lunar and Planetary Institute
Solar System Overview This image shows the Sun and 8 planets approximately to scale. The order of these bodies are: Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. By the Lunar and Planetary Institute FYI … Distance Not To Scale … Image: Lunar and Planetary Laboratory:

The Sun At the Center (and we do go around it …..)
99.85% mass of Solar System 92% H / 8% He Source of solar wind and space weather Genesis Mission – solar wind SOHO SOHO Image Extreme Ultraviolet Imaging Telescope (EIT) image of a huge, handle-shaped prominence taken on Sept. 14,1999 taken in the 304 angstrom wavelength - Prominences are huge clouds of relatively cool dense plasma suspended in the Sun's hot, thin corona. At times, they can erupt, escaping the Sun's atmosphere. Emission in this spectral line shows the upper chromosphere at a temperature of about 60,000 degrees K. Every feature in the image traces magnetic field structure. The hottest areas appear almost white, while the darker red areas indicate cooler temperatures. More information on Sun at And at And at Image:

Inner Planets “Terrestrial Planets” Rocky Dense Metal cores (iron)
Images: Lunar and Planetary Laboratory:

Asteroids Ida “Minor planets” or “planetoids” less than 1000 km across
Asteroid Belt between Mars and Jupiter Occasionally run into Earth and other planets (oops) Ida This view of the asteroid 243 Ida was acquired by the Galileo spacecraft at ranges of 3,057 to 3,821 kilometers (1,900 to 2,375 miles) on August 28, 1993, about 3.5 minutes before the spacecraft made its close approach to the asteroid. This view shows numerous craters, including many degraded craters larger than any seen on Gaspra. The south pole is believed to be in the dark side near the middle of the asteroid. (Courtesy NASA/JPL) More information on asteroids at: And at Image:

Outer Planets Large! Gases and liquids No solid surface
May have a small solid core Tumultuous atmospheres - rapid winds, large storms Rotate relatively quickly Image: Lunar and Planetary Laboratory:

Kuiper Belt Disk of debris at the edge of our Solar System
Pluto is a KB Object (sorry!) Source of short-period comets Image from Information from The Nine Planets:

Oort Cloud Sphere of widely spaced comets, dust
30 trillion km from Sun Long-period comets (random time and direction) Information on Sedna at This object is the most distant body known that orbits our Sun. It is at present over 90 AUs away, 3 times as far as Pluto. Sedna is about 1800 km in diameter, slightly smaller than Pluto. Relative position of Sedna to Kuiper Belt: NASA/JPL-Caltech/R. Hurt (SSC-Caltech) Artist’s conception of Sedna: NASA/JPL-Caltech/R. Hurt (SSC-Caltech)

Some more data to explain:
4. Most planets rotate in this same direction Mercury 0° Venus 177° Earth 23° Mars 25° Jupiter 3° Saturn 27° Uranus 98° Neptune 30° NASA images edited by LPI

Inner Planets! Impact cratering, volcanism, tectonics
Each planet expresses these processes with unique signature Common thread? HEAT Inner Planets! Image: Lunar and Planetary Laboratory:

Mercury Smallest planet (0.4 Earth diam)
#1, Coffee Bean Smallest planet (0.4 Earth diam) Closest to Sun, moves around fastest (88 days) Surface -173 to 427 ºC (-280 to 800 ºF) ? Ice Caps – no tilt of axis so poles are cold No atmosphere Mariner 3 fly-bys in 1974 and – 40% of surface mapped Information about Mercury at And at Image:

What are these? How did they form?
Original Caption Released with Image: Antoniadi Ridge, over 450 kilometers long, runs along the right side of this image. The ridge transects a large crater (80-km in diameter) and in turn appears to be interrupted by an irregular rimless depression on the floor of the crater. This ridge also crosses smooth plains to the north and intercrater plains to the south of the large crater. This image (FDS 27325) was acquired during the spacecraft's first encounter with Mercury. The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon. Image Credit: NASA/JPL/Northwestern University Mariner image from:

Impact Crater Diagram Schematic cross sections of (a) a simple crater and (b) a complex crater showing idealized form, structure and distribution of impact units. Simple crater forms are typical of structures with rim diameters of less than about 4 kilometers (on Earth); above this transition diameter, craters are characterized by complex morphologies exhibiting central uplifts, shallow floor depths, and slumped rims. For complex craters with diameters of about 4 to 50 kilometers the central uplift occurs as a single peak. Larger impact structures can have complex, ring-shaped central uplifts. Image Credit: NASA Graphic from

Original Caption Released with Image:
Thrust faults: The radius of Mercury decreased by miles after the solidification and impact cratering of the surface. This was probably due to the cooling of the planet. Original Caption Released with Image: Intercrater plains and heavily cratered terrain typical of much of Mercury outside the area affected by the formation of the Caloris basin are shown in this image (FDS 27488) taken during the spacecraft's first encounter with Mercury. Abundant shallow elongate craters and crater chains are present on the intercrater plains. Large tract of intercrater plains centered at 3 degrees N, 20 degrees W. Prominent scarp Santa Maria Rupes cuts both intercrater plains and old craters. North is to the top of this image which is 200 kilometers across. The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon. Image Credit: NASA/JPL/Northwestern University Mariner image at

Mercury Dense! 5.43 g/cc Surface is made of lighter stuff (spectrum similar to Moon) 75% iron and nickel – large core – size of moon Why so large? Magnetic field - Molten?? Remnant?? Geologically inactive by ~3.7 Billion Years Ago Why so much iron? 1) heaviest stuff closest to sun – hot and refractory materials collected here; or 2) impact – blew off outer lighter layer of mantle. Mercury Cools As Mercury cooled it contracted. Its cold outer crust broke and slivers of crust thrust over each other, forming rough-edged ridges. Mercury's surface has been geologically inactive for about the last 3.7 billion years, other than occasional impacts. Mercury Mercury has an average density of 5430 kilograms per cubic meter, which is second only to Earth among all the planets. It is estimated that the planet Mercury, like Earth, has a ferrous core with a size equivalent to two-thirds to three-fourths that of the planet's overall radius. The core is believed to be composed of an iron-nickel alloy covered by a mantle and surface crust. Image by LPI:

MESSENGER Mission to Mercury
March 2011 will enter orbit More information at Images from

Information about Venus at http://www.nineplanets.org/venus.html
NASA Image:

Venus #2, Large Blueberry Nearly the same size as Earth (.95)
Slowest rotation of any planet (243 days) Spins backwards Surface temp 377 to 487 C 710 to 908 F … hotter than Mercury Cloud covered – radar observations Dry! Very thick atmosphere mostly CO2 Surface pressure is 100 times higher than Earth’s Runaway greenhouse P MGN-114 May 26, 1993 This global view of the surface of Venus is centered at 90 degrees east longitude. Magellan synthetic aperture radar mosaics from the three eight-month cycles of Magellan radar mapping are mapped onto a computer-simulated globe to create this image. Magellan obtained coverage of 98 percent of the surface of Venus. Remaining gaps are filled with data from previous Venus missions -- the Venera 15 and 16 radar and Pioneer-Venus Orbiter altimetry -- and data from Earth-based radar observations from the Arecibo radio telescope. Simulated color is used to enhance small-scale structures. The simulated hues are based on color images obtained by the Venera 13 and 14 landing craft. The bright feature near the center of the image is Ovda Regio, a mountainous region in the western portion of the great Aphrodite equatorial highland. The dark areas scattered across the Venusian plains consist of extremely smooth deposits associated with large meteorite impacts. The image was produced by the Solar System Visualization Project and the Magellan Science team at the Jet Propulsion Laboratory Multimission Image Processing Laboratory. The Magellan mission is managed by JPL for NASA's Office of Space Science. Lots of information about Venus at Can see it in the night sky without a telescope! Magellan image from

Where Do Atmospheres Come From?
Image from LPI:

All Planets with Volcanism – Including Earth!
Primarily carbon dioxide about 10 miles high winds strong high in the atmosphere, but only slight breeze at surface sulfuric acid droplets atmospheric pressure at surface is 92 times Earth’s reflects a lot of sunlight, making Venus appear bright (high albedo) Only Earth (As far as we know …) NOTE: Not required for life! Images from LPI: and

Venera Images Venus was visited by Mariner 2 in It has been visited by many others (more than 20 in all so far), including Pioneer Venus and the Soviet Venera 7 the first spacecraft to land on another planet, and Venera 9 which returned the first photographs of the surface. The first orbiter, the US spacecraft Magellan Magellan radar map (false color) produced detailed maps of Venus' surface using radar. ESA's Venus Express is now in orbit with a large variety of instruments. Mariner 2 Fly-by in 1962; 20 “visits” since, including Venera landers and Magellan Orbiter Image:

Sapas Mons – 1.5 km (0.9 mi) high, 400 km (248 mi) across Atla Regio
Volcanic flood plains cover 85% of surface 1100 volcanic centers identified Original Caption Released with Image: This false-color image shows the volcano Sapas Mons, which is located in the broad equatorial rise called Atla Regio (8 degrees north latitude and 188 degrees east longitude). The area shown is approximately 650 kilometers (404 miles) on a side. Sapas Mons measures about 400 kilometers (248 miles) across and 1.5 kilometers (0.9 mile) high. Its flanks show numerous overlapping lava flows. The dark flows on the lower right are thought to be smoother than the brighter ones near the central part of the volcano. Many of the flows appear to have been erupted along the flanks of the volcano rather than from the summit. This type of flank eruption is common on large volcanoes on Earth, such as the Hawaiian volcanoes. The summit area has two flat-topped mesas, whose smooth tops give a relatively dark appearance in the radar image. Also seen near the summit are groups of pits, some as large as one kilometer (0.6 mile) across. These are thought to have formed when underground chambers of magma were drained through other subsurface tubes and lead to a collapse at the surface. A 20 kilometer-diameter (12-mile diameter) impact crater northeast of the volcano is partially buried by the lava flows. Little was known about Atla Regio prior to Magellan. The new data, acquired in February 1991, show the region to be composed of at least five large volcanoes such as Sapas Mons, which are commonly linked by complex systems of fractures or rift zones. If comparable to similar features on Earth, Atla Regio probably formed when large volumes of molten rock upwelled from areas within the interior of Venus known as'hot spots.' Magellan is a NASA spacecraft mission to map the surface of Venus with imaging radar. The basic scientific instrument is a synthetic aperture radar, or SAR, which can look through the thick clouds perpetually shielding the surface of Venus. Magellan is in orbit around Venus which completes one turn around its axis in 243 Earth days. That period of time, one Venus day, is the length of a Magellan mapping cycle. The spacecraft completed its first mapping cycle and primary mission on May 15, 1991, and immediately began its second cycle. During the first cycle, Magellan mapped more than 80 percent of the planet's surface and the current and subsequent cycles of equal duration will provide complete mapping of Venus. Magellan was launched May 4, 1989, aboard the space shuttle Atlantis and went into orbit around Venus August 10, 1990. Image Note: C1-MIDR 09N188 Magellan image at

Aphrodite Terra Region
Maat Mons – 8 km (5 mi) high, Aphrodite Terra Region Original Caption Released with Image: Maat Mons is displayed in this computer generated three-dimensional perspective of the surface of Venus. The viewpoint is located 634 kilometers (393 miles) north of Maat Mons at an elevation of 3 kilometers (2 miles) above the terrain. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground, to the base of Maat Mons. The view is to the south with the volcano Maat Mons appearing at the center of the image on the horizon and rising to almost 5 kilometers (3 miles) above the surrounding terrain. Maat Mons is located at approximately 0.9 degrees north latitude, degrees east longitude with a peak that ascends to 8 kilometers (5 miles) above the mean surface. Maat Mons is named for an Egyptian Goddess of truth and justice. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. The vertical scale in this perspective has been exaggerated 10 times. Rays cast in a computer intersect the surface to crate a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the April 22, 1992 news conference. NASA Image:

Alpha Regio—Pancake Domes
This image shows a collection of volcanic features given the colorful nickname “pancake domes.” The steep sides of these features and their apparent emplacement in a single episode of volcanism has led to models of formation that seem to require a highly viscous, perhaps silicic, magma. These particular domes are located just southeast of Alpha Regio at 30°S, 12°E and can be seen in the slide of that region. NASA Image from LPI:

What’s missing on Venus?
Few impact craters – what does this tell us? No craters less than 3 km (meteoroid ~ 30 m across) Atmospheric filter

No interior data, density similar to earth; so probably a core
Surface million years old Few, random craters, sharp edges Basalts No magnetic field; solid core Probably geologically active – convection in mantle Kinda flat… 60% of surface within 500 m of 0; 5% >2 km Highs and lows, but about 60% within 500 m of mean Volcanic flood plains cover 85% of surface 1100 volcanic centers identified Small shield volcanoes – circular outlines Intermediate constructs km flat topped steep sided thick lava – best evidence for silica lava Largest at 100 km and bigger – lava flows Basalts – flow look and venera camera shots – looks like basalt! Wrinkle ridges ( km long, 1 km wide – compressive Rifts (chasma) - extensional Isolated continental blocks – Ishtar with Maxwell Mons (Maxwell, chemist), the highest point at 12 km It is believed that the composition of the planet Venus is similar to that of Earth. The planet crust extends to around kilometers below the surface, under which the mantle reaches to a depth of some 3000 kilometers. The planet core comprises a liquid iron-nickel alloy. Average planet density is 5240 kilograms per cubic meter. Image from LPI:

Earth #3, Cherry 7900 mile (12756 km) diameter
23 degree axis tilt (seasons!) Surface temps –73 to 48 C (-100 to 120F) Thick atmosphere, mild greenhouse effect Liquid water – lots! - at surface Information and statistics at Can see it without a telescope!

Geologically active? Core, mantle, crust Magnetic field?
The Earth comprises three separate layers: a crust, a mantle, and a core (in descending order from the surface). The crust thickness averages 30 kilometers for land masses and 5 kilometers for seabeds. The mantle extends from just below the crust to some 2900 kilometers deep. The core below the mantle begins at a depth of around 5100 kilometers, and comprises an outer core (liquid iron-nickel alloy) and inner core (solid iron-nickel alloy). The crust is composed mainly of granite in the case of land masses and basalt in the case of seabeds. The mantle is composed primarily of peridotite and high-pressure minerals. Average planet density is 5520 kilograms per cubic meter. Image from LPI:

Who Cares About a Magnetic Field?
We do! Information at National Geophysical Data Center, Artist: E. Endo

Mars #4, Pea 6794 km diameter (4,220 miles) – about ½ of Earth’s
Can see it in the night sky without a telescope! 6794 km diameter (4,220 miles) – about ½ of Earth’s 25 degree axis tilt (seasons!) Rotates once every ~24 hours and orbits the Sun once every 687 days Very cold -83 to -33 C (-117 to -27 F) Thin atmosphere, 95% CO2, & 3% N No liquid water at surface; ice in poles and regolith? Two small moons - Phobos (Fear) and Deimos (Terror) Information at Image caption: Global Mosaic of Mars Centered on Valles Marineris Date: Global mosaic of 102 Viking 1 Orbiter images of Mars taken on orbit 1,334, 22 February The images are projected into point perspective, representing what a viewer would see from a spacecraft at an altitude of 2,500 km. At center is Valles Marineris, over 3000 km long and up to 8 km deep. Note the channels running up (north) from the central and eastern portions of Valles Marineris to the dark area, Acidalic Planitia, at upper right. At left are the three Tharsis volcanoes and to the south is ancient, heavily impacted terrain. (Viking 1 Orbiter, MG07S SP) Image Credit: NASA NASA image from 0

Mars Surface gravity: 38%
About like Mercury’s, because of Mars’ low density Core Crust – thick – supports huge volcanoes No magnetic field – had one because meteorites do; solid core? Meteorites – 180 million year old basalts Mars Mars is roughly one-half the diameter of Earth. Due to its small size, it is believed that the martian center has cooled. Geological structure is mainly rock and metal. The mantle below the crust comprises iron-oxide-rich silicate. The core is made up of an iron-nickel alloy and iron sulfide. Average planet density is 3930 kilograms per cubic meter. Image from LPI:

The MOLA laser altimeter produced detailed topographic maps and profiles of Mars, and really revolutionized our understanding of Mars. So much from elevation alone! These maps show the MOLA altitude data coded into colors - blue is low and red/white are high. The basins and volcanos show very clearly Image available at

Western edge of Tharsis Region
The volcanoes of the Tharsis region are highlighted by this color image mosaic obtained on a single martian afternoon by the Mars Orbiter Camera (MOC)onboard the Mars Global Surveyor (MGS) spacecraft. Olympus Mons dominates the upper left corner--it is one of the largest known volcanoes and is nearly 550 km (340 miles) wide. The grayscale image on the right shows the name of each volcano in the scene. The white or bluish-white features are clouds. Clouds are common over the larger Tharsis volcanoes in mid-afternoon. The four largest volcanoes are more than 15 km (9 mi) high. Viewed from Earth by telescope before any spacecraft had visited the planet, astronomers often described a "W"-shaped white cloud over the Tharsis region. This "W" was actually the result of seeing the combined effects of bright clouds hanging over the Ascraeus, Pavonis, Arsia, and Olympus volcanoes. The clouds result when warm air containing water vapor rises up the slopes of each volcano, cools at the higher altitude, and causes the water vapor to freeze and form a cloud of ice crystals. Pavonis Mons lies on the martian equator, north is up, and sunlight is illuminating the scene from the left. The picture is a mosaic of red and blue filter images taken on three consecutive orbits. The slightly blurred appearance of the left side of Arsia Mons results from distortion toward the edges of the images used to make the mosaic. To remove the blur, an image obtained on another day would be added to the mosaic--however, this image would not match well because the cloud patterns will have changed by the next day. Mosaics such as the one shown here are used to monitor changes in martian weather and to plan future observations. Image Credit: NASA/JPL/MSSS Tharsis Bulge: 2,500 miles across 6 miles high MGS images at:

Dune Fields, Wind Streaks, Dust Storms
Sand Dunes in Kaiser Crater This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) high resolution image shows a field of dark sand dunes on the floor of Kaiser Crater in southeastern Noachis Terra. The steepest slopes on each dune, the slip faces, point toward the east, indicating that the strongest winds that blow across the floor of Kaiser move sand in this direction. Wind features of three different scales are visible in this image: the largest (the dunes) are moving across a hard surface (light tone) that is itself partially covered by large ripples. These large ripples appear not to be moving--the dunes are burying some and revealing others. Another type of ripple pattern is seen on the margins of the dunes and where dunes coalesce. They are smaller (both in their height and in their separation) than the large ripples. These are probably coarse sediments that are moving with the dunes. This picture covers an area approximately 3 km (1.9 mi) across and is illuminated from the upper left. Photo Credit: NASA/JPL/Malin Space Science Systems Wind Streaks: This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows dark wind streaks on a plain east of Olympus Mons in the Tharsis region of Mars. Streaks such as these change from time to time over the course of a martian year, suggesting that they are the result of wind movement of a thin layer of bright dust. In other words, wind is not moving dark material to make the dark streaks, it is removing bright material (thin coatings of dust). This picture is located near 16.3°N, 127.7°W. The image covers an area 3 km (1.9 mi) across and is illuminated by sunlight from the upper left. MGS image at MGS image at Hubble image of Mars at

Caps expand and contract during seasonal changes
MGS image of ice cap: Viking image at Water ice and dust in cap; winter CO2 layer forms, sublimates in spring Dark band = dune fields Color Image of Frost at Utopia Planitia on Mars This color image shows a thin layer of water ice frost on the martian surface at Utopia Planitia. It was taken by Viking 2 Lander camera 2 on 18 May 1979, almost exactly one martian year (687 days) after frost first appeared at this spot and was imaged by Viking 2. The layer is thought to be only a couple thousandths of a centimeter thick. It is speculated that dust particles in the atmosphere pick up tiny bits of water. When it gets cold enough for carbon dioxide to solidify, some of it attaches to the dust and ice and it falls to the surface. The view is looking towards the south southeast, the long boulder to the right is roughly one meter across. (Viking 2 Lander, P-21873 South Polar Cap This is the south polar cap of Mars as it appeared to the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) on April 17, In winter and early spring, this entire scene would be covered by frost. In summer, the cap shrinks to its minimum size, as shown here. Even though it is summer, observations made by the Viking orbiters in the 1970s showed that the south polar cap remains cold enough that the polar frost (seen here as white) consists of carbon dioxide. Carbon dioxide freezes at temperatures around -125° C (-193° F). Mid-summer afternoon sunlight illuminates this scene from the upper left from about 11.2° above the horizon. Soon the cap will experience sunsets; by June 2000, this pole will be in autumn, and the area covered by frost will begin to grow. Winter will return to the south polar region in December The polar cap from left to right is about 420 km (260 mi) across. Photo Credit: NASA/JPL/Malin Space Science Systems Original Caption Released with Image: The north polar cap is visible in this projection at the top of the image, the great equatorial canyon system (Valles Marineris) below center, and four huge Tharsis volcanoes (and several smaller ones) at left. Also note heavy impact cratering of the highlands (bottom and right portions of this mosaic) and the younger, less heavily cratered terrains elsewhere. North polar cap is probably water-ice South polar cap is primarily frozen carbon dioxide Water ice and dust CO2 layer – winter Caps expand and contract during seasonal changes Viking Image at

Liquid Water in the Past?
M-01 Information from LIQUID WATER ON MARS Valley Network (42°S,92°W) Many valley systems on Mars do not show evidence for catastrophic flooding. Instead, they show a greater resemblance to drainage systems on Earth, where water acts at slow rates over long periods of time. The valleys in this image are much smaller than the channels shown in slides #23–#25. As on Earth, the channels shown here merge together to form larger channels. However, these valley networks are less developed than typical terrestrial drainage systems, with the martian examples lacking small-scale streams feeding into the larger valleys. Because of the absence of small-scale streams in the martian valley networks, it is thought that the valleys were carved primarily by groundwater flow rather than by runoff of rain. Although liquid water is currently unstable on the surface on Mars, theoretical studies indicate that flowing groundwater might be able to form valley networks if the water flowed beneath a protective cover of ice. Alternatively, because the valley networks are confined to relatively old regions on Mars, their presence may indicate that Mars once possessed a warmer and wetter climate in its early history. The area shown is about 200 kilometers across. From Mars Digital Image Map, image processing by Brian Fessler, Lunar and Planetary Institute 10 km Viking image from:

Possibly lots of water ~3.5 – 4 billion years ago … acidic, salty ….
Past Oceans on Mars? Current thinking – Water = yes Possibly lots of water ~3.5 – 4 billion years ago … acidic, salty …. Image: LPI

landed on Mars January 3 and January 24, 2004
Mars Rovers information at landed on Mars January 3 and January 24, 2004 Searched for rocks and soils that hold clues to past water activity on Mars The landing sites were Gusev Crater, a possible former lake in a giant impact crater, and Meridiani Planum, where mineral deposits (hematite) suggest Mars had a wet past. January 24, 2006 Mars Rovers Advance Understanding of the Red Planet NASA's Mars rovers, Spirit and Opportunity, have been working overtime to help scientists better understand ancient environmental conditions on the red planet. The rovers are also generating excitement about the exploration of Mars outlined in NASA's Vision for Space Exploration. The rovers continue to find new variations of bedrock in areas they are exploring on opposite sides of Mars. The geological information they have collected adds evidence about ancient Martian environments that included periods of wet, possibly habitable conditions. "The extended journeys taken by the two rovers across the surface of Mars has allowed the science community to continue to uncover discoveries that will enable new investigations of the red planet far into the future." said Mary Cleave, associate administrator for the Science Mission Directorate, NASA Headquarters. In late November 2005 while descending "Husband Hill," Spirit took the most detailed panorama to date of the "Inner Basin." Image credit: NASA/JPL/Cornell Large Image NASA's third mission extension for the rovers lasts through September 2006, if they remain usable that long. During their three-month primary missions, the rovers drove farther and examined more rocks than the prescribed criteria for success. Opportunity begins its third year on Mars today. It is examining bedrock exposures along a route between "Endurance" and "Victoria" craters. Opportunity found evidence of a long-ago habitat of standing water on Mars. On Jan. 3, Spirit passed its second anniversary inside the Connecticut-sized Gusev Crater. Initially, Spirit did not find evidence of much water, and hills that might reveal more about Gusev's past were still mere bumps on the horizon. By operating eight times as long as planned, Spirit was able to climb up those hills, examine a wide assortment of rocks and find mineral fingerprints of ancient water. While showing signs of wear, Spirit and Opportunity are still being used to their maximum remaining capabilities. On Spirit, the teeth of the rover's rock abrasion tool are too worn to grind the surface off any more rocks, but its wire-bristle brush can still remove loose coatings. The tool was designed to uncover three rocks, but it exposed interiors of 15 rocks. On Opportunity, the steering motor for the front right wheel stopped working eight months ago. A motor at the shoulder joint of the rover's robotic arm shows symptoms of a broken wire in the motor winding. Opportunity can still maneuver with its three other steerable wheels. Its shoulder motor still works when given extra current, and the arm is still useable without that motor. The rovers are two of five active robotic missions at Mars, which include NASA's Mars Odyssey and Mars Global Surveyor and the European Space Agency's Mars Express orbiters. The orbiters and surface missions complement each other in many ways. Observations by the rovers provide ground-level understanding for interpreting global observations by the orbiters. In addition to their own science missions, the orbiters relay data from Mars. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of the California Institute of Technology, manages the Mars Exploration Rover, Odyssey and Global Surveyor projects for NASA's Science Mission Directorate. Artwork from

The Gas Giants Image: Lunar and Planetary Laboratory:

Small rocky cores – hot? cold? Mostly hydrogen and helium
Information available at Gas Giant Interiors Jupiter Jupiter's composition is mainly hydrogen and helium. In contrast to planetary bodies covered with a hard surface crust (the Earth, for example), the jovian surface is gaseous-liquid, rendering the boundary between the atmosphere and the planet itself almost indistinguishable. Below the roughly 1000-kilometer-thick atmosphere, a layer of liquid hydrogen extends to a depth of 20,000 kilometers. Even deeper, it is believed that there is a layer of liquid metallic hydrogen at a pressure of 3 million bars. The planet core is believed to comprise iron-nickel alloy, rock, etc., at a temperature estimated to exceed 20,000C. Saturn As with Jupiter, Saturn is mainly composed of hydrogen and helium and is observed to be of extremely low density. In fact, Saturn's mean density is only about two-thirds that of water. The Saturn atmosphere comprises, in descending order of altitude, a layer of ammonia, a layer of ammonium hydrogen sulfide, and a layer of ice. Below this, the saturnian surface is a stratum of liquid hydrogen (as in the case of Jupiter) underlain with a layer of liquid metallic hydrogen. It is believed that the liquid hydrogen layer of Saturn is thicker than that of Jupiter, while the liquid metallic hydrogen layer may be thinner. The planet's core is estimated to be composed of rock and ice. Uranus Uranus is gaseous in composition, mainly comprising hydrogen and helium as in the case of Jupiter and Saturn. The planet atmosphere is mostly hydrogen but also includes helium and methane. The planet core is estimated to be rock and ice encompassed by an outer layer of ice comprised of water, ammonium, and methane. Neptune The atmosphere of Neptune consists of mainly hydrogen, methane and helium, similar to Uranus. Below it is a liquid hydrogen layer including helium and methane. The lower layer is made up of the liquid hydrogen compounds oxygen and nitrogen. It is believed that the planet core comprises rock and ice. Neptune's average density, as well as the greatest proportion of core per planet size, is the greatest among all the gaseous planets. Image Credit: Lunar and Planetary Institute Small rocky cores – hot? cold? Mostly hydrogen and helium Where’s the surface? LPI Image, from:

Jupiter #5, Small Cantaloupe
89,000 miles (143,000 km) diameter – 11x Earth 2x mass of all other planets combined (318 x Earth); 100 pounds on Earth = 254 on Jupiter 90% H and 10% He (75/25% by mass) Methane, water, ammonia, rock Rocky core – liquid metallic hydrogen – electrical conductor, generates magnetic field Similar to Solar Nebula Jupiter was first visited by Pioneer 10 in 1973 and later by Pioneer 11, Voyager 1, Voyager 2 and Ulysses. The spacecraft Galileo orbited Jupiter for eight years. It is still regularly observed by the Hubble Space Telescope. More information at Image at

Jupiter Cloud-tops average = -153°C = -244°F.
Can see it in the night sky without a telescope! Cloud-tops average = -153°C = -244°F. 10 hour rotation / 12 year orbit Fly-bys: Pioneer 10, 11, Voyager 1, 2, Ulysses (2/04), Cassini Orbiter: Galileo – 8 years (recently “visited” the planet), Probe Original Caption Released with Image: This true-color simulated view of Jupiter is composed of 4 images taken by NASA's Cassini spacecraft on December 7, To illustrate what Jupiter would have looked like if the cameras had a field-of-view large enough to capture the entire planet, the cylindrical map was projected onto a globe. The resolution is about 144 kilometers (89 miles) per pixel. Jupiter's moon Europa is casting the shadow on the planet. Cassini is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages Cassini for NASA's Office of Space Science, Washington, D.C. Image Credit: NASA/JPL/University of Arizona Released November 13, 2003 Everything visible on the planet is a cloud. The parallel reddish-brown and white bands, the white ovals, and the large Great Red Spot persist over many years despite the intense turbulence visible in the atmosphere. The most energetic features are the small, bright clouds to the left of the Great Red Spot and in similar locations in the northern half of the planet. These clouds grow and disappear over a few days and generate lightning. Streaks form as clouds are sheared apart by Jupiter's intense jet streams that run parallel to the colored bands. The prominent dark band in the northern half of the planet is the location of Jupiter's fastest jet stream, with eastward winds of 480 kilometers (300 miles) per hour. Jupiter's diameter is eleven times that of Earth, so the smallest storms on this mosaic are comparable in size to the largest hurricanes on Earth. Unlike Earth, where only water condenses to form clouds, Jupiter's clouds are made of ammonia, hydrogen sulfide, and water. The updrafts and downdrafts bring different mixtures of these substances up from below, leading to clouds at different heights. The brown and orange colors may be due to trace chemicals dredged up from deeper levels of the atmosphere, or they may be byproducts of chemical reactions driven by ultraviolet light from the Sun. Bluish areas, such as the small features just north and south of the equator, are areas of reduced cloud cover, where one can see deeper. For more information, see the Cassini Project home page, and the Cassini imaging team home page, The imaging team is based at the Space Science Institute, Boulder, Colo. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Office of Space Science, Washington, D.C. Image at

Jupiter Moons Galileo – 1610 – Four “Galilean” Moons of Jupiter
Image from Jupiter/Galilean Satellites: When Galileo first turned his telescope toward Jupiter four centuries ago, he saw that the giant planet had four large satellites, or moons. These, the largest of dozens of moons that orbit Jupiter, later became known as the Galilean satellites. The larger two, Callisto and Ganymede, are roughly the size of the planet Mercury; the smallest, Io and Europa, are approximately the size of Earth's Moon. This MGS MOC image, obtained from Mars orbit on 8 May 2003, shows Jupiter and three of the four Galilean satellites: Callisto, Ganymede, and Europa. At the time, Io was behind Jupiter as seen from Mars, and Jupiter's giant red spot had rotated out of view. This image has been specially processed to show both Jupiter and its satellites, since Jupiter, at an apparent magnitude of -1.8, was much brighter than the three satellites. Image Credit: NASA/JPL/Malin Space Science Systems Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa. A faint mist of particles can be seen above and below the main rings; this vertically extended "halo" is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. Jupiter's main ring is a thin strand of material encircling the planet. The diffuse innermost boundary begins at approximately 123,000 km. The main ring's outer radius is found to be at 128,940 +/-50 km, slightly less than the Voyager value of 129,130 +/-100 km, but very close to the orbit of the satellite Adrastea (128,980 km). The main ring exhibits a marked drop in brightness at 127,849 +/-50 km, lying almost atop the orbit of the jovian moon Metis at 127,978 km. Satellites seem to affect the structure of even tenuous rings like that found at Jupiter. Image Note: Galileo Callisto 3 Orbit Galileo – 1610 – Four “Galilean” Moons of Jupiter (Io behind Jupiter) 63 moons … and counting Rings! Rocky particles, no ice Image from

Storms on Jupiter Giant Red Spot – at least 300 years old
3 x size of Earth Winds up to 400 km / hr “Jr” Merger of white ovals over 3 years beginning in 1998 gave us Jr. Both storms wheel around the planet in longitude as Jupiter rotates, but are latitudinally locked in their own narrow bands in the southern hemisphere ABOUT THIS IMAGE: NASA's Hubble Space Telescope is giving astronomers their most detailed view yet of a second red spot emerging on Jupiter. For the first time in history, astronomers have witnessed the birth of a new red spot on the giant planet, which is located half a billion miles away. The storm is roughly one-half the diameter of its bigger and legendary cousin, the Great Red Spot. Researchers suggest that the new spot may be related to a possible major climate change in Jupiter's atmosphere. Dubbed by some astronomers as "Red Spot Jr.," the new spot has been followed by amateur and professional astronomers for the past few months. But Hubble's new images provide a level of detail comparable to that achieved by NASA's Voyager 1 and 2 spacecraft as they flew by Jupiter a quarter-century ago. Before it mysteriously changed to the same color as the Great Red Spot, the smaller spot was known as the White Oval BA. It formed after three white oval-shaped storms merged during 1998 to At least one or two of the progenitor white ovals can be traced back to 90 years ago, but they may have been present earlier. A third spot appeared in (The Great Red Spot has been visible for the past 400 years, ever since earthbound observers had telescopes to see it). When viewed at near-infrared wavelengths (specifically 892 nanometers — a methane gas absorption band) Red Spot Jr. is about as prominent in Jupiter's cloudy atmosphere as the Great Red Spot. This may mean that the storm rises miles above the top of the main cloud deck on Jupiter just as its larger cousin is thought to do. Some astronomers think the red hue could be produced as the spots dredge up material from deeper in Jupiter's atmosphere, which is then chemically altered by the Sun's ultraviolet light. Researchers think the Hubble images may provide evidence that Jupiter is in the midst of a global climate change that will alter its average temperature at some latitudes by as much as 10 degrees Fahrenheit. The transfer of heat from the equator to the planet's south pole is predicted to nearly shut off at 34 degrees southern latitude, the latitude where the second red spot is forming. The effects of the shut-off were predicted by Philip Marcus of the University of California, Berkeley (UCB) to become apparent approximately seven years after the White Oval collisions in 1998 to 2000. Two teams of astronomers were given discretionary time on Hubble to observe the new red spot. [Left] — This image, acquired April 8, 2006 with Hubble's Advanced Camera for Surveys (high-resolution channel), shows that the second red spot has a small amount of pale clouds in the center. A strong convective event, which is likely a thunderstorm, is visible as a bright white cloud north of the oval, in the turbulent clouds that precede the Great Red Spot. As the oval continues its eastward drift and the Great Red Spot moves westward, they should pass each other in early July. This contrast-enhanced image was taken in blue and red light. The group that performed this observation was led by Amy Simon-Miller (NASA Goddard Space Flight Center), Glenn Orton (Jet Propulsion Laboratory) and Nancy Chanover (New Mexico State University). [Right] — Hubble's Advanced Camera for Surveys (wide field channel) took this image of the entire disk of Jupiter on April 16. The second red spot appears at southern latitudes, below the center of Jupiter's disk. The new spot is approximately the size of Earth's diameter. The image was taken in visible light and at near-infrared wavelengths, and does not represent Jupiter's true colors. The red color traces high-altitude haze blankets: the equatorial zone, the Great Red Spot, the second red spot, and the polar hoods. The Hubble group that conducted this observation is led jointly by Imke de Pater (UCB Astronomy) and Philip Marcus (UCB Mechanical Engineering). Other team members are Michael Wong (UCB Astronomy), Xylar Asay-Davis (UCB Mechanical Engineering), and Christopher Go, an amateur astronomer with the Astronomical League of the Philippines. Hubble images of Great Red Spot at

Aurora Jupiter Aurora In this Hubble telescope picture, a curtain of glowing gas is wrapped around Jupiter's north pole like a lasso. This curtain of light, called an aurora, is produced when high-energy electrons race along the planet's magnetic field and into the upper atmosphere where they excite atmospheric gases, causing them to glow. The aurora resembles the same phenomenon that crowns Earth's polar regions. But this Hubble image, taken in ultraviolet light, also shows the glowing "footprints" of three of Jupiter's largest moons: Io, Ganymede, and Europa. Spanning next two months in 2004, Jupiter's aurora will be scrutinized by two observatories: the Hubble telescope and the Cassini spacecraft, which will fly by the planet on its voyage to Saturn. Image Credit: John Clarke (University of Michigan) and NASA Hubble image from

Electrically Charged Atmosphere - Lightening Flashes
The jovian atmosphere is not only dynamic and turbulent but is electrically charged, as is evident from this next view that shows lightning-like discharges, imaged when the Orbiter is looking at the nightside of Jupiter's outer atmosphere. These are the first visible lightning flashes seen on another planet. Original Caption Released with Image: The knots of light which have been circled in yellow in this false color picture probably represent lightning in Jupiter's atmosphere. The picture was taken at 5 hours 3 minutes Universal Time on November 9, 1996 through the clear filter of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft. The largest of the circled spots is over 500 kilometers across, comparable in size to the lightning events seen by NASA's Voyager 2 spacecraft in 1979, but much larger than the single lightning flashes seen by Voyager 1. Thus each of the larger circled spots represents either multiple flashes within a large lightning storm, or a single flash illuminating a much higher cloud. The planetocentric latitude lines imposed on this image indicate that the circled events lie at about 44 degrees North latitude, just below a westward moving jet at 46 degrees North. Almost all of the Jovian lightning seen by Voyager similarly occurred near the latitude of a westward moving jet. Moreover, the circled events occurred in Jupiter's most atmospherically active high latitude region (between 36 and 46 degrees North), which is one of the zones where lightning is most likely. In order to detect lightning the camera was scanned horizontally across the darkside of Jupiter, starting just inside the eastern edge of the planet and ending just inside its western edge. The scanning motion was employed both to cover the largest possible longitude range, and to help separate lightning strokes emanating from the same storm. Several of the circled spots are relatively elongated in the east-west direction, perhaps due to the scanning motion of the camera (and/or to a foreshortening in the north-south direction caused by the curvature of the planet). The circled events appear well separated in space, and any apparent separation in latitude is real. Because of the scanning motion of the camera, however, these events may not have been truly separated in longitude. It is even possible that they all came from the same localized storm, and were separated principally in time. Diffuse light covers much of this picture, and is particularly bright in the bottom righthand corner. Some of this emission may be moonlit clouds, but much of it is likely sunlight scattered into the camera by the atmosphere along Jupiter's edge. At the time of this observation Galileo was in Jupiter's shadow, and located about 2.3 million kilometers (about 32 Jovian radii) from the planet. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC. This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL Background information and educational context for the images can be found at URL Electrically Charged Atmosphere - Lightening Flashes Galileo image from

Io Average surface temperature of –150 C
Thin, patchy atmosphere of sulfur compounds No known liquid water Highly volcanic More information available at Galileo’s telescopic observations of Jupiter in 1610 revealed the presence of four moons orbiting the planet; Io, Europa, Ganymede, and Callisto are now collectively known as the Galilean satellites. In March 1979, the Voyager 1 spacecraft discovered nine active volcanos erupting material up to 100 kilometers (60 miles) above the surface of Io, an object comparable in size to Earth’s Moon. Nearly 17 years later, the Galileo spacecraft (in orbit around Jupiter since 1995) observed some of those same volcanos still active, while others had ceased erupting and new volcanic centers had started erupting. This striking image of Io was taken on September 7, 1996, with the clouds of Jupiter as a backdrop. The bright ring around a dark spot near the center of the disk is the product of one of the active eruptions; the other dark spots may be volcanos that were not active during the spacecraft encounters. The unusual coloration of Io is largely a result of variations in the color of sulfur that is widely distributed across its surface. The power source for this tremendous volcanic activity is a flexing of the crust and mantle of Io resulting from competing gravitational pulls exerted by Jupiter, Europa, and Ganymede. Galileo Press Release P NASA Gallileo Image at:

Io Original Caption Released with Image:
This pair of images taken by NASA's Galileo spacecraft captures a dynamic eruption at Tvashtar Catena, a chain of volcanic bowls on Jupiter's moon Io. They show a change in the location of hot lava over a period of a few months in 1999 and early 2000. The image on the left uses data obtained on Nov. 26 and July 3, 1999, at resolutions of 183 meters (600 feet) and 1.3 kilometers (0.8 miles) per pixel, respectively. The red and yellow lava flow itself is an illustration based upon imaging data. The image on the right is a composite using a five-color observation made on Feb. 22, 2000, at 315 meters (1030 feet) per pixel. These are among the most fortuitous observations made by Galileo because this style of volcanism is too unpredictable and short-lived to plan to photograph. Short-lived bursts of volcanic activity on Io had been previously detected from Earth-based observations, but interpreting the style of volcanic activity from those lower-resolution views was highly speculative. These Galileo observations confirm hypotheses that the initial, intense thermal output comes from active lava fountains. Galileo's high-resolution observations of volcanic activity on Io have also confirmed other hypotheses based on earlier, low-resolution data. These include interpretations of slowly spreading lava flows at Prometheus and Amirani and an active lava lake at Pele. These tests of earlier hypotheses increase scientists' confidence in interpreting volcanic activity seen in low-resolution remote sensing data of Earth as well as Io. However, these data are still of insufficient resolution to adequately test the more quantitative models that have been applied to volcanic eruptions on Earth and Io. These images also show other geologic features on Io, such as the scalloped margins of the plateau to the northeast of the active lavas. These margins appear to have formed by sapping, a process usually associated with springs of water. Liquid sulfur dioxide might be the fluid responsible for sapping on Io. A better understanding of sapping on Io will influence how scientists interpret similar features on Mars(where the viability of carbon dioxide or water as the sapping fluid remains controversial). The individual images in this composite can be viewed separately in the PIA02545 (left hand image) and PIA02550 (right hand image) photojournal entries. Images and data received from Galileo are posted on the Galileo mission home page at Background information and educational context for the images can be found athttp:// The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. NASA Galileo image at:

Europa Average surface temperature –145C
Ice cap - 1 to 10 km thick – water? Sulfur? Ocean 60 to 100 km thick – water? Salty? No atmosphere Tidal heat? Volcanic activity? Smooth surface areas over hot regions? More information at This image shows two views of the trailing hemisphere (it is always opposite the direction of motion) of Jupiter’s moon Europa, the second Galilean satellite moving outward from Jupiter. The view on the left is an approximate natural color view of Europa, taken by the Galileo spacecraft on September 7, The view on the right is the same image but with colors enhanced by computer to highlight subtle variations on the icy surface. Europa is about the same size as Io and Earth’s Moon, with a water-ice surface crisscrossed by numerous dark fractures and a prominent impact crater at lower right. The brown regions near the center of the images may include rock and mud mixed with the ice. Galileo obtained many high-resolution images of Europa that show that fracturing has occurred on many scales and intensities. Galileo Press Release P EUROPA Europa is the smallest of Jupiter's four planet-sized moons, yet it is only slightly smaller than Earth's Moon. Its bright surface (roughly five times as reflective as the Moon), infrared water ice absorption bands, and the near absence of impact craters (only about five have been identified to date) indicate that the surface is ice rich and very young, perhaps only 30 million years old. Europa is covered by a water-ice shell no more than 150 kilometers thick. Calculations suggest that there could be liquid water at the base of this icy layer, leading to speculation that a primitive life form could have evolved in this dark, watery world. The thickness of the surface ice and the possible presence of liquid water have intrigued planetary scientists since the late 1970s. Europa was the most poorly observed of the Galilean satellites when Voyager passed through the Jupiter system in 1979, and scientists eagerly anticipate Galileo's first images of this fractured icy world. NASA Galileo image at:

Europa Freckles on europa – galileo image Caption Released with Image:
Reddish spots and shallow pits pepper the enigmatic ridged surface of Europa in this view combining information from images taken by NASA's Galileo spacecraft during two different orbits around Jupiter. The spots and pits visible in this region of Europa's northern hemisphere are each about 10 kilometers (6 miles) across. The dark spots are called "lenticulae," the Latin term for freckles. Their similar sizes and spacing suggest that Europa's icy shell may be churning away like a lava lamp, with warmer ice moving upward from the bottom of the ice shell while colder ice near the surface sinks downward. Other evidence has shown that Europa likely has a deep melted ocean under its icy shell. Ruddy ice erupting onto the surface to form the lenticulae may hold clues to the composition of the ocean and to whether it could support life. Galileo Image at

Ganymede largest moon in Solar System; bigger than Mercury rock, with bright (younger) patches and dark (older) patches older regions may be 4 billion years old has tectonics with ice crust may have salty ocean beneath ice crust Information at Image from

Callisto large like Ganymede but heavily cratered and dark
mostly made of ice and rock, without a real core craters are “mushy”; not eroded exactly... strong new evidence of salty ocean underneath an ice crust Information at Image from

Saturn #6, Large Orange 9x the size of Earth
75% hydrogen and 25% helium Water, methane, ammonia and "rock“ Rocky core Winds up to 500 m / second -290 F Rings – 185,00 miles wide / /2 mi thick Water ice in rings 56 moons and counting 11 hour rotation / 29 year orbit Pioneer / Voyager Fly-by / Cassini/Huygens! 155,000 miles in diameter / ½ mile thick – rings Saturn is the sixth planet from the Sun and the second largest: orbit: 1,429,400,000 km (9.54 AU) from Sun diameter: 120,536 km (equatorial) mass: 5.68e26 kg Ring image from More information at

Can see it in the night sky without a telescope!
Cassini image at:

Rather chilly in the rings Red: -261 F Blue -333 F Green -298 F
False Color Rather chilly in the rings Red: -261 F Blue -333 F Green -298 F Image from: ../multimedia/images/rings/images/PIA06425.jpg&type=image Saturn's Rings, Cold and Colder False-color image from the Cassini spacecraft shows the temperature of Saturn's rings. Red represents temperatures of about -261 degrees Fahrenheit, and blue of -333 degrees Fahrenheit. Green is equivalent to -298 degrees Fahrenheit. Water freezes at 32 degrees Fahrenheit. Dirty Snow Turquoise= water ice Red = “dirty”

Merging Saturnian Storms April 8, 2004 Full-Res: PIA Three months before its scheduled arrival at Saturn, the Cassini spacecraft has observed two storms in the act of merging. With diameters close to 1,000 kilometers (621 miles), both storms, which appear as spots in the southern hemisphere, were seen moving west, relative to the rotation of Saturn's interior, for about a month before they merged on March 19 through 20, This set of eight images was taken between Feb. 22 and March 22, The top four frames span 26 days. They are portions of images from the narrow angle camera taken through a filter accepting light in the near-infrared region of the spectrum centered at 619 nanometers, and they show two storms approaching each other. Both storms are located at 36 degrees south latitude and sit in an anti-cyclonic shear zone, which means that the flow to the north is westward relative to the flow to the south. Consequently, the northern storm moves westward at a slightly greater rate than the southern one, 11 meters versus 6 meters per second (25 and 13 mph), respectively. The storms drift with these currents and engage in a counterclockwise dance before merging with each other. The bottom four frames are from images taken on March 19, 20, 21 and 22, in a region of the spectrum visible to the human eye; they illustrate the storms' evolution. Just after the merger, on March 20, the new feature is elongated in the north-south direction, with bright clouds on either end. Two days later, on March 22, the storm has settled into a more circular shape, and the bright clouds have spread around the circumference to form a halo. Whether the bright clouds are particles of a different composition or simply at a different altitude is uncertain. The new storm is a few tenths of a degree farther south than either of its progenitors. There, its westward velocity is weaker, and it is almost stationary relative to the planet's rotation. Although these particular storms move slowly west, storms at Saturn's equator move east at speeds up to 450 meters per second (1,000 mph), which is 10 times the speed of Earth's jet streams and three times greater than the equatorial winds on Jupiter. Saturn is the windiest planet in the solar system, which is another mystery of the ringed giant. The image scale ranges from 381 kilometers (237 miles) to 300 kilometers (186 miles) per pixel. All images have been processed to enhance visibility. Cassini image at

Titan! Clues to Early Earth?
Information on Titan at Hovering Over Titan A mosaic of images shows brightness variations across the surface and bright clouds near the south pole of Titan. Scientists are working to understand the images. There are no obvious impact craters. However, the exact nature of that activity, whether tectonic, wind-blown, river, marine or volcanic is still to be determined. Cassini image from:

Titan Clues to Early Earth?
Average surface temperature –179C Atmosphere of N (>90%), CH4, Ar Hydrocarbon-rich rivers/seas (ethane – C2H6) Water ice Atmosphere 1.5 x Earth Titan Clues to Early Earth? Left image: Original Caption Released with Image: This Voyager 2 photograph of Titan, taken Aug. 23 from a range of 2.3 million kilometers (1.4 million miles), shows some detail in the cloud systems on this Saturnian moon. The southern hemisphere appears lighter in contrast, a well-defined band is seen near the equator, and a dark collar is evident at the north pole. All these bands are associated with cloud circulation in Titan's atmosphere. The extended haze, composed of submicron-size particles, is seen clearly around the satellite's limb. This image was composed from blue, green and violet frames. Right image: Purple Haze—Titan’s Atmosphere Encircled in purple stratospheric haze, Titan appears as a softly glowing sphere in this colorized image taken one day after Cassini's first flyby of that moon. This image shows two thin haze layers. The outer haze layer is detached and appears to float high in the atmosphere. Because of its thinness, the high haze layer is best seen at the moon's limb. The image was taken using a spectral filter sensitive to wavelengths of ultraviolet light centered at 338 nanometers. The image has been falsely colored: The globe of Titan retains the pale orange hue our eyes usually see, and both the main atmospheric haze and the thin detached layer have been brightened and given a purple color to enhance their visibility. The best possible observations of the detached layer are made in ultraviolet light because the small haze particles which populate this part of Titan's upper atmosphere scatter short wavelengths more efficiently than longer visible or infrared wavelengths. Images like this one reveal some of the key steps in the formation and evolution of Titan's haze. The process is thought to begin in the high atmosphere, at altitudes above 400 kilometers (250 miles), where ultraviolet light breaks down methane and nitrogen molecules. The products are believed to react to form more complex organic molecules containing carbon, hydrogen and nitrogen that can combine to form the very small particles seen as haze. The bottom of the detached haze layer is a few hundred kilometers above the surface and is about 120 kilometers (75 miles) thick. Voyager image at Cassini image at

This artist's rendering shows Titan's surface with Saturn dimly visible in the background through Titan's thick atmosphere of methane, ethane and (mostly) nitrogen. The Cassini spacecraft flies over the surface with its high-gain antenna pointed at the Huygens probe as it reaches the surface. Thin methane clouds dot the horizon and a narrow methane spring, or "methanefall," flows from the cliff and drifts mostly into vapor. Smooth ice features rise out of the methane/ethane lake, and crater walls can be seen far in the distance. Image credit: Craig Attebery

Titan is the largest of Saturn's moons, bigger than the planets Mercury and Pluto. The study of Titan is one of the major goals of the Cassini-Huygens mission because it may preserve, in deep-freeze, many of the chemical compounds that preceded life on Earth. Huygens image from:

January 14, 2005 - Colored view of Titan following image processing (close to actual color).
Initially thought to be rocks or ice blocks, the chunks are pebble-sized. The objects below the middle of the image are about 6 inches (left) and about 1.5 inches (center) across respectively. The surface is darker than expected, consisting of a mixture of water and hydrocarbon ice. There is also evidence of erosion at the base of the objects, indicating possible water action. Original Caption Released with Image: This image was returned yesterday, January 14, 2005, by the European Space Agency's Huygens probe during its successful descent to land on Titan. This is the colored view, following processing to add reflection spectra data, and gives a better indication of the actual color of the surface. Initially thought to be rocks or ice blocks, they are more pebble-sized. The two rock-like objects just below the middle of the image are about 15 centimeters (about 6 inches) (left) and 4 centimeters (about 1.5 inches) (center) across respectively, at a distance of about 85 centimeters (about 33 inches) from Huygens. The surface is darker than originally expected, consisting of a mixture of water and hydrocarbon ice. There is also evidence of erosion at the base of these objects, indicating possible fluvial activity. The image was taken with the Descent Imager/Spectral Radiometer, one of two NASA instruments on the probe. Huygens image at :

Cratered Worlds Phoebe Mimas
Mimas is a battered, impact crater covered world. The largest impact basin is Herschel, 130 km across. Cassini image PIA06582. Caption Released with Mimas Image: Saturn's moon Mimas has many large craters, but its Herschel crater dwarfs all the rest. This large crater 130 kilometers wide (80 miles) has a prominent central peak, seen here almost exactly on the terminator. This crater is the moon's most prominent feature, and the impact that formed it probably nearly destroyed Mimas. Mimas is 398 kilometers (247 miles) across. This view is predominantly of the leading hemisphere of Mimas. The image has been rotated so that north on Mimas is up. The Face of Phoebe Date: Phoebe's true nature is revealed in startling clarity in this mosaic of two images taken during Cassini's flyby on June 11, The image shows evidence for the emerging view that Phoebe may be an ice-rich body coated with a thin layer of dark material. Small bright craters in the image are probably fairly young features. This phenomenon has been observed on other icy satellites, such as Ganymede at Jupiter. When impactors slammed into the surface of Phoebe, the collisions excavated fresh, bright material -- probably ice -- underlying the surface layer. Further evidence for this can be seen on some crater walls where the darker material appears to have slid downwards, exposing more light-colored material. Some areas of the image that are particularly bright - especially near lower right - are over-exposed. An accurate determination of Phoebe's density -- a forthcoming result from the flyby -- will help Cassini mission scientists understand how much of the little moon is comprised of ices. For more information, about the Cassini-Huygens mission visit, and the Cassini imaging team home page, . Phoebe Mimas Cassini images from: And

Dione from Cassini Dione
This high resolution Cassini image, PIA06162, shows that the wispy terrain on Dione is indeed due to faulting! Sitting in the tranquility of space is the pale moon Dione, looking as if it's posing for a painter. The moon is set against the stunning backdrop of Saturn, adorned in gold and draped with hues of blue. Breathtaking views and a movie of the icy world are now available at and . During the Cassini spacecraft's only close flyby of the grayish moon, on Oct. 11, 2005, the spacecraft came within 500 kilometers (310 miles) of the surface. Like most of its counterparts in the Saturnian system, Dione shows a heavily cratered surface. It has a signature style all its own that includes streaky terrains dominating one whole side of the moon. The fine latitudinal streaks appear to crosscut everything and appear to be the youngest feature type in this region of Dione. These striking cracks and fractures are caused by tectonic activity. "Dione seems to be an older sibling of Enceladus," said Dr. Bonnie Buratti, scientist on the Cassini visual and infrared mapping spectrometer team at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We think that the cracked features of Dione may be the older version of the tiger stripes on Enceladus. Enceladus is the up-and-coming moon, complete with a recently active history, while Dione is the older, more mature moon." The Cassini infrared spectrometer team is working on compositional maps of the moon's surface. As it departed its encounter with Saturn¿s moon Dione, Cassini sailed above an unreal landscape blasted by impacts. The rising Sun throws craters into sharp contrast and reveals steep crater walls. Multiple generations of fractures are visible on Dione. Numerous fine, roughly parallel grooves run across the terrain and are interrupted by the larger, irregular, bright fractures. In several places, fractures postdate some deposits in the bottoms of craters. The Cassini ultraviolet imaging spectrograph team reports the detection of water ice on the surface of Dione and also finds striking brightness variations across the surface. This could be the result of cracks and fractures in the ice. "The ice in the fractures appears to be different than in the surrounding terrain. This may be due to the grain size variations," said Dr. Amanda Hendrix, Cassini scientist at JPL. As on other Saturnian moons, rockslides on Dione may reveal cleaner ice, while the darker materials accumulate in areas of lower topography, such as crater floors and the bases of scarps. Scientists on the Cassini fields and particles instruments note that early results do not support the presence of an atmosphere. Dione orbits Saturn within the broad, tenuous E-ring. Hence, scientists will be looking to see if Dione, like Enceladus, is a source of material in the E-ring. They also seek to learn whether the E-ring is affecting Dione's surface. Over the coming months, scientists will begin to piece together a more detailed story of Dione. Cassini image from:

Enceladus Despite its small size, Enceladus shows evidence for substantial geologic activity. Much of the surface is free of large craters, suggesting relatively recent volcanic flows that resurfaced the plains. The numerous lineaments visible on Enceladus are probably faults. Voyager image. Cassini Finds an Active, Watery World at Saturn's Enceladus July 29, 2005 (Source: NASA/JPL) Enceladus Temperature Map Saturn's tiny icy moon Enceladus, which ought to be cold and dead, instead displays evidence for active ice volcanism. NASA's Cassini spacecraft has found a huge cloud of water vapor over the moon's south pole, and warm fractures where evaporating ice probably supplies the vapor cloud. Cassini has also confirmed Enceladus is the major source of Saturn's largest ring, the E-ring. "Enceladus is the smallest body so far found that seems to have active volcanism," said Dr. Torrence Johnson, Cassini imaging-team member at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Enceladus' localized water vapor atmosphere is reminiscent of comets. 'Warm spots' in its icy and cracked surface are probably the result of heat from tidal energy like the volcanoes on Jupiter's moon Io. And its geologically young surface of water ice, softened by heat from below, resembles areas on Jupiter's moons, Europa and Ganymede." Enceladus Atmosphere Cassini flew within 175 kilometers (109 miles) of Enceladus on July 14. Data collected during that flyby confirm an extended and dynamic atmosphere. This atmosphere was first detected by the magnetometer during a distant flyby earlier this year. The ion and neutral mass spectrometer and the ultraviolet imaging spectrograph found the atmosphere contains water vapor. The mass spectrometer found the water vapor comprises about 65 percent of the atmosphere, with molecular hydrogen at about 20 percent. The rest is mostly carbon dioxide and some combination of molecular nitrogen and carbon monoxide. The variation of water vapor density with altitude suggests the water vapor may come from a localized source comparable to a geothermal hot spot. The ultraviolet results strongly suggest a local vapor cloud. The fact that the atmosphere persists on this low-gravity world, instead of instantly escaping into space, suggests the moon is geologically active enough to replenish the water vapor at a slow, continuous rate. "For the first time we have a major clue not only to the role of water at the icy moons themselves, but also to its role in the evolution and dynamics of the Saturn system as a whole," said Dr. Ralph L. McNutt, ion and neutral mass spectrometer-team member, Johns Hopkins University Applied Physics Laboratory, Laurel, Md. Enceladus Atmosphere -- Star Struck Images show the south pole has an even younger and more fractured appearance than the rest of Enceladus, complete with icy boulders the size of large houses and long, bluish cracks or faults dubbed "tiger stripes." Another Cassini instrument, the composite infrared spectrometer, shows the south pole is warmer than anticipated. Temperatures near the equator were found to reach a frigid 80 degrees Kelvin (minus 316 Fahrenheit), as expected. The poles should be even colder because the Sun shines so obliquely there. However, south polar average temperatures reached 85 Kelvin (minus 307 Fahrenheit), much warmer than expected. Small areas of the pole, concentrated near the "tiger stripe" fractures, are even warmer: well over 110 Kelvin (minus 261 Fahrenheit) in some places. "This is as astonishing as if we'd flown past Earth and found that Antarctica was warmer than the Sahara," said Dr. John Spencer, team member of the composite infrared spectrometer, Southwest Research Institute, Boulder, Colo. Scientists find the temperatures difficult to explain if sunlight is the only heat source. More likely, a portion of the polar region, including the "tiger stripe" fractures, is warmed by heat escaping from the interior. Evaporation of this warm ice at several locations within the region could explain the density of the water vapor cloud detected by other instruments. How a 500-kilometer (310-mile) diameter moon can generate this much internal heat and why it is concentrated at the south pole is still a mystery. Cassini's cosmic dust analyzer detected a large increase in the number of particles near Enceladus. This observation confirms Enceladus is a source of Saturn's E-ring. Scientists think micrometeoroids blast the particles off, forming a steady, icy, dust cloud around Enceladus. Other particles escape, forming the bulk of the E ring. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. Additional information and graphics on these results are available at: and . Cassini image from:

Enceladus from Cassini
Enceladus from Cassini’s 1st close flyby, Feb PIA06191, resolution meters/pixel. This part of Enceladus is heavily dissected by extensional (pull apart) faults. Cassini Finds Enceladus Tiger Stripes are Really Cubs August 30, 2005 (Source: Jet Propulsion Laboratory) This visual and infrared mapping spectrometer image of Enceladus shows the dark cracks at the south pole dubbed "tiger stripes" for their distinct stripe-like appearance. Superimposed on top of the map is a "crystallinity" map that shows the freshest, most crystal ice as blue. The Cassini spacecraft has discovered the long, cracked features dubbed "tiger stripes" on Saturn's icy moon Enceladus are very young -- between 10 and 1,000 years young. These findings support previous results showing the moon's southern pole is active. The pole had episodes of geologic activity as recently as 10 years ago. These cracked features are approximately 130 kilometers long (80 miles), spaced about 40 kilometers (25 miles) apart and run roughly parallel to one another. The cracks act like vents. They spew vapor and fine ice water particles that have become ice crystals. This crystallization process can be dated, which helped scientists pin down the age of the features. "There appears to be a continual supply of fresh, crystalline ice at the tiger stripes, which could have been very recently resurfaced," said Dr. Bonnie Buratti. She is a team member of the Cassini visual and infrared mapping spectrometer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Enceladus is constantly evolving and getting a makeover." This finding is especially exciting because ground-based observers have seen tiny Enceladus brighten as its south pole was visible from Earth. Cassini allows scientists to see close up that the brightening is caused by geologic activity. When NASA's Voyager 2 spacecraft flew over the moon's north pole in 1981, it did not observe the tiger stripes. Cassini's visual and infrared mapping spectrometer shows water ice exists in two forms on Enceladus: in pristine, crystalline ice and radiation-damaged amorphous ice. When ice comes out of the "hot" cracks, or "tiger stripes," at the south pole, it forms as fresh, crystalline ice. As the ice near the poles remains cold and undisturbed, it ages and converts to amorphous ice. Since this process is believed to take place over decades or less, the tiger stripes must be very young. "One of the most fascinating aspects of Enceladus is that it is so very small as icy moons go, but so very geophysically active. It's hard for a body as small as Enceladus to hold onto the heat necessary to drive such large-scale geophysical phenomena, but it has done just that," said Dr. Bob Brown. Brown is a team leader for the visual and infrared mapping spectrometer at the University of Arizona, Tucson. "Enceladus and its incredible geology is a marvelous puzzle for us to figure out." Adding to the already mounting evidence for an active body is the correlation of results from multiple instruments. Cassini's cameras provided detailed images of the south polar cap, in which the tiger stripe fractures were found to be among the hottest features. The timing of the craft's ion and neutral mass spectrometer and the cosmic dust analyzer observations seems to indicate the vapor and fine material are originating from the "hot" polar cap region. These data also indicate the production of water vapor and ejection of fine material are connected, as they are in a comet. This suggests that vapor and dust-sized icy material are coming from the tiger stripes. Enceladus is on a short list of bodies in our solar system where scientists have found internal activity. The others are the volcanoes on Jupiter's moon Io and geysers on Neptune's moon Triton. Data for these measurements were taken during Cassini's closest flyby on July 14, The spacecraft came within 175 kilometers (109 miles) of the surface of Enceladus. Enceladus is 500 kilometers (314 miles) across and has the most reflective surface in the solar system. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. Cassini images from:

Geysers of water jet from surface of Enceladus
Recent Cassini images of Saturn's moon Enceladus backlit by the sun show the fountain-like sources of the fine spray of material that towers over the south polar region. This image was taken looking more or less broadside at the "tiger stripe" fractures observed in earlier Enceladus images. It shows discrete plumes of a variety of apparent sizes above the limb (edge) of the moon. Imaging scientists, as reported in the journal Science on March 10, 2006, believe that the jets are geysers erupting from pressurized subsurface reservoirs of liquid water above 273 degrees Kelvin (0 degrees Celsius). This caption was updated on March 9, 2006. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo. For more information about the Cassini-Huygens mission visit The Cassini imaging team homepage is at Image Credit: NASA/JPL/Space Science Institute Enceladus Races Onward April 5, 2006 Full-Res: PIA As our robotic emissary to Saturn, the Cassini spacecraft is privileged to behold such fantastic sights as this pairing of two moons beyond the rings. The bright, narrow F ring is the outermost ring structure seen here. In this scene, bright Enceladus (505 kilometers, or 314 miles across) begins to slip in front of more distant Dione (1,126 kilometers, or 700 miles across). Enceladus is closer to Saturn than Dione, and orbits the planet at greater velocity. Thus, the smaller moon eventually passed the larger one, as seen from the Cassini spacecraft, and continued on its way. The image was taken with the Cassini spacecraft narrow-angle camera on March 3, 2006, using a filter sensitive to wavelengths of ultraviolet light centered at 338 nanometers and at a distance of approximately 2.6 million kilometers (1.6 million miles) from Enceladus and 2.7 million kilometers (1.7 million miles) from Dione. The view was taken from a phase angle (Sun-moon-spacecraft angle) of 139 degrees; about the same angle with respect to both moons. Image scale is about 16 kilometers (10 miles) per pixel on Enceladus and Dione. For more information about the Cassini-Huygens mission visit . The Cassini imaging team homepage is at . Credit: NASA/JPL/Space Science Institute Cassini images from: and

Iapetus Cassini image PIA Details of the contact between bright and dark terrain will help to determine the origin of the two units. The impact basin on the right limb is 400 km in diameter. The equatorial ridge is 20 km wide and 13 km high! Saturn's Moon Iapetus Shows a Bulging Waistline January 7, 2005 (Source: Jet Propulsion Laboratory / Space Science Institute) Iapetus in 3D More Iapetus Images Images returned by NASA's Cassini spacecraft cameras during a New Year's Eve flyby of Saturn's moon Iapetus (eye-APP-eh-tuss) show startling surface features that are fueling heated scientific discussions about their origin. One of these features is a long narrow ridge that lies almost exactly on the equator of Iapetus, bisects its entire dark hemisphere and reaches 20 kilometers high (12 miles). It extends over 1,300 kilometers (808 miles) from side to side, along its midsection. No other moon in the solar system has such a striking geological feature. In places, the ridge is comprised of mountains. In height, they rival Olympus Mons on Mars, approximately three times the height of Mt. Everest, which is surprising for such a small body as Iapetus. Mars is nearly five times the size of Iapetus. Images from the flyby are available at and . Iapetus is a two-toned moon. The leading hemisphere is as dark as a freshly-tarred street, and the white, trailing hemisphere resembles freshly-fallen snow. The flyby images, which revealed a region of Iapetus never before seen, show feathery-looking black streaks at the boundary between dark and bright hemispheres that indicate dark material has fallen onto Iapetus. Opinions differ as to whether this dark material originated from within or outside Iapetus. The images also show craters near this boundary with bright walls facing towards the pole and dark walls facing towards the equator. Cassini's next close encounter with Iapetus will occur in September The resolution of images from that flyby should be 100 times better than the ones currently being analyzed. The hope is that the increased detail may shed light on Iapetus' amazing features and the question of whether it has been volcanically active in the past. With a diameter of about 1,400 kilometers (890 miles), Iapetus is Saturn's third largest moon. It was discovered by Jean-Dominique Cassini in It was Cassini, for whom the Cassini-Huygens mission is named, who correctly deduced that one side of Iapetus was dark, while the other was white. Encountering Iapetus More Iapetus Images The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The European Space Agency built and manages the development of the Huygens probe and is in charge of the probe operations. The Italian Space Agency provided the high-gain antenna, much of the radio system and elements of several of Cassini's science instruments. The imaging team is based at the Space Science Institute, Boulder, Colo. Cassini image from:

Uranus # 7, Kiwi First planet discovered with a telescope!
Information on Uranus at Hubble image at

Uranus 4x the size of Earth 15% H, little helium – mostly ices
Uniform through out; no rocky core Blue from methane absorption of red light (atmosphere) atmosphere has mostly hydrogen and helium 11 rings, 27 satellites -350 F at surface 18 hour rotation, 84 year orbit Spins on an axis inclined almost 90 degrees Voyager fly-by First telescopic discovery of a planet (Herschel; 1781) Original Caption Released with Image: These two pictures of Uranus were compiled from images recorded by Voyager 2 on Jan. 1O, 1986, when the NASA spacecraft was 18 million kilometers (11 million miles) from the planet. The images were obtained by Voyager's narrow-angle camera; the view is toward the planet's pole of rotation, which lies just left of center. The picture on the left has been processed to show Uranus as human eyes would see it from the vantage point of the spacecraft. The second picture is an exaggerated false-color view that reveals details not visible in the true-color view -- including indications of what could be a polar haze of smog-like particles. The true-color picture was made by combining pictures taken through blue, green and orange filters. The dark shading of the upper right edge of the disk is the terminator, or day-night boundary. The blue-green appearance of Uranus results from methane in the atmosphere; this gas absorbs red wavelengths from the incoming sunlight, leaving the predominant bluish color seen here. The picture on the right uses false color and contrast enhancement to bring out subtle details in the polar region of the atmosphere. Images shuttered through different color filters were added and manipulated by computer, greatly enhancing the low-contrast details in the original images. Ultraviolet, violet- and orange-filtered images were displayed, respectively, as blue, green and red to produce this false-color picture. The planet reveals a dark polar hood surrounded by a series of progressively lighter convective bands. The banded structure is real, though exaggerated here. The brownish color near the center of the planet could be explained as being caused by a thin haze concentrated over the pole -- perhaps the product of chemical reactions powered by ultraviolet light from the Sun. One such reaction produces acetylene from methane -- acetylene has been detected on Uranus by an Earth-orbiting spacecraft -- and further reactions involving acetylene are known to produce reddish-brown smog-like particles. A similar haze envelopes Saturn's moon Titan; ground-based observations have predicted such a haze in the polar regions of Uranus. The exact identification of the reactions and their products will require additional study. Voyager 2 is heading for a Jan. 24 closest approach to Uranus. The Voyager project is managed for NASA by the Jet Propulsion Laboratory. Image Note: blue - PICNO 0068U2-014 red - PICNO 0192U2-014 green - PICNO 0204U2-014 Images from

Uranus Original Caption Released with Rings Image:
Hubble Image from: Original Caption Released with Rings Image: Voyager 2 returned this picture of the Uranus rings on Jan. 22, 1986, from a distance of 2.52 million kilometers (1.56 million miles). All nine known rings are visible in this image, a 15-second exposure through the clear filter on Voyager's narrow-angle camera. The rings are quite dark and very narrow. The most prominent and outermost of the nine, called epsilon, is seen at top. The next three in toward Uranus -- called delta, gamma and eta -- are much fainter and more narrow than the epsilon ring. Then come the beta and alpha rings and finally the innermost grouping, known simply as the 4, 5 and 6 rings. The last three are very faint and are at the limit of detection for the Voyager camera. Uranus' rings range in width from about 100 km (60 mi) at the widest part of the epsilon ring to only a few kilometers for most of the others. This image was processed to enhance these narrow features; the bright dots are imperfections on the camera detector. The resolution scale is approximately 50 km (30 mi). The Voyager project is managed for NASA by the Jet Propulsion Laboratory. Original Caption Released with Hubble Image of Uranus’ Atmosphere: Hubble Space Telescope has peered deep into Uranus' atmosphere to see clear and hazy layers created by a mixture of gases. Using infrared filters, Hubble captured detailed features of three layers of Uranus' atmosphere. Hubble's images are different from the ones taken by the Voyager 2 spacecraft, which flew by Uranus 10 years ago. Those images - not taken in infrared light - showed a greenish-blue disk with very little detail. The infrared image allows astronomers to probe the structure of Uranus' atmosphere, which consists of mostly hydrogen with traces of methane. The red around the planet's edge represents a very thin haze at a high altitude. The haze is so thin that it can only be seen by looking at the edges of the disk, and is similar to looking at the edge of a soap bubble. The yellow near the bottom of Uranus is another hazy layer. The deepest layer, the blue near the top of Uranus, shows a clearer atmosphere. Image processing has been used to brighten the rings around Uranus so that astronomers can study their structure. In reality, the rings are as dark as black lava or charcoal. Bottom Hubble image: A recent Hubble Space Telescope view reveals Uranus surrounded by its four major rings and by 10 of its 17 known satellites. This false-color image was generated by Erich Karkoschka using data taken on August 8, 1998, with Hubble's Near Infrared Camera and Multi-Object Spectrometer. Hubble recently found about 20 clouds — nearly as many clouds on Uranus as the previous total in the history of modern observations. The orange-colored clouds near the prominent bright band circle the planet at more than 300 mph (500 km/h), according to team member Heidi Hammel (MIT). One of the clouds on the right-hand side is brighter than any other cloud ever seen on Uranus. The colors in the image indicate altitude. Team member Mark Marley (New Mexico State University) reports that green and blue regions show where the atmosphere is clear and sunlight can penetrate deep into Uranus. In yellow and grey regions the sunlight reflects from a higher haze or cloud layer. Orange and red colors indicate very high clouds, such as cirrus clouds on Earth. The Hubble image is one of the first images revealing the precession of the brightest ring with respect to a previous image [LINK to PRC97-36a]. Precession makes the fainter part of the ring (currently on the upper right-hand side) slide around Uranus once every nine months. The fading is caused by ring particles crowding and hiding each other on one side of their eight-hour orbit around Uranus. The blue, green and red components of this false-color image correspond to exposures taken at near-infrared wavelengths of 0.9, 1.1, and 1.7 micrometers. Thus, regions on Uranus appearing blue, for example, reflect more sunlight at 0.9 micrometer than at the longer wavelengths. Apparent colors on Uranus are caused by absorption of methane gas in its atmosphere, an effect comparable to absorption in our atmosphere which can make distant clouds appear red. Object Name: Uranus Image Type: Astronomical CREDIT: Erich Karkoschka (University of Arizona) and NASA Voyager 2 Image from: Hubble Image from:

Neptune #8, Apricot or nectarine
Information on Neptune at Original Caption Released with Image: Neptune's blue-green atmosphere is shown in greater detail than ever before by the Voyager 2 spacecraft as it rapidly approaches its encounter with the giant planet. This color image, produced from a distance of about 16 million kilometers, shows several complex and puzzling atmospheric features. The Great Dark Spot (GDS) seen at the center is about 13,000 km by 6,600 km in size -- as large along its longer dimension as the Earth. The bright, wispy "cirrus-type" clouds seen hovering in the vicinity of the GDS are higher in altitude than the dark material of unknown origin which defines its boundaries. A thin veil often fills part of the GDS interior, as seen on the image. The bright cloud at the southern (lower) edge of the GDS measures about 1,000 km in its north-south extent. The small, bright cloud below the GDS, dubbed the "scooter," rotates faster than the GDS, gaining about 30 degrees eastward (toward the right) in longitude every rotation. Bright streaks of cloud at the latitude of the GDS, the small clouds overlying it, and a dimly visible dark protrusion at its western end are examples of dynamic weather patterns on Neptune, which can change significantly on time scales of one rotation (about 18 hours). Image Note: Green - PICNO 1736N2-012Blue - PICNO 1742N2-012Red - PICNO 1749N2-012 Image from:

Neptune Ices and rock - 15% H and little He
H, He, methane atmosphere (blue!) Uniform through out; small rocky core? Had storm “Great Dark Spot” MIA since Voyager 2 Pretty Good White Spot (Scooter) zipped around every 16 hours…. 4 Rings – unknown composition 13 moons 18 hour rotation / 165 year orbit Voyager (1989) Original Caption Released with Image: Neptune's blue-green atmosphere is shown in greater detail than ever before by the Voyager 2 spacecraft as it rapidly approaches its encounter with the giant planet. This color image, produced from a distance of about 16 million kilometers, shows several complex and puzzling atmospheric features. The Great Dark Spot (GDS) seen at the center is about 13,000 km by 6,600 km in size -- as large along its longer dimension as the Earth. The bright, wispy "cirrus-type" clouds seen hovering in the vicinity of the GDS are higher in altitude than the dark material of unknown origin which defines its boundaries. A thin veil often fills part of the GDS interior, as seen on the image. The bright cloud at the southern (lower) edge of the GDS measures about 1,000 km in its north-south extent. The small, bright cloud below the GDS, dubbed the "scooter," rotates faster than the GDS, gaining about 30 degrees eastward (toward the right) in longitude every rotation. Bright streaks of cloud at the latitude of the GDS, the small clouds overlying it, and a dimly visible dark protrusion at its western end are examples of dynamic weather patterns on Neptune, which can change significantly on time scales of one rotation (about 18 hours). Image Note: Green - PICNO 1736N2-012Blue - PICNO 1742N2-012Red - PICNO 1749N2-012 This bulls-eye view of Neptune's small dark spot (D2) was obtained by Voyager 2's narrow-angle camera. Banding surrounding the feature indicates unseen strong winds, while structures within the bright spot suggest both active upwelling of clouds and rotation about the center. A rotation rate has not yet been measured, but the V-shaped structure near the right edge of the bright area indicates that the spot rotates clockwise. Unlike the Great Red Spot on Jupiter, which rotates counterclockwise, if the D2 spot on Neptune rotates clockwise, the material will be descending in the dark oval region. The fact that infrared data will yield temperature information about the region above the clouds makes this observation especially valuable. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications. PICNO 0441N2-001 Image from

Triton Ice volcanos-- geysers Thin atmosphere (nitrogen, methane)
Ridges and valleys, melting Good information at Image: Image:

Pluto Grain of Rice Information on Pluto at Image from

Pluto Diameter - 1,413 miles (2274 km) - 2/3 size of Earth’s Moon
Rotation: 6 1/3 days Orbit: 248 years highly elliptical Sometimes is inside Neptune’s orbit (20 yrs) Light from Sun takes 5.5 hours to reach it Surface of water and methane ice, frozen nitrogen When closer to the Sun, heat produces an atmosphere Image can be found at

November 1, 2005: Using NASA's Hubble Space Telescope to probe the ninth planet in our solar system, astronomers have discovered that Pluto may have not one, but three moons. Right: An artist's concept of the Pluto system as seen from the surface of one of the candidate moons. [More] Pluto was discovered in The planet resides 3 billion miles from the sun in the heart of the Kuiper Belt, a vast region of icy, rocky bodies beyond Neptune's orbit. In 1978, astronomers discovered Charon, Pluto's only confirmed moon. "If, as our new Hubble images indicate, Pluto has not one, but two or three moons, it will become the first body in the Kuiper Belt known to have more than one satellite," said Hal Weaver of the Johns Hopkins Applied Physics Laboratory, Laurel, Md. He is co-leader of the team that made the discovery. The candidate moons, provisionally designated S/2005 P1 and S/2005 P2, are approximately 27,000 miles (44,000 kilometers) away from Pluto--in other words, two to three times as far from Pluto as Charon. These are tiny moons. Their estimated diameters lie between 40 and 125 miles (64 and 200 kilometers). Charon, for comparison, is about 730 miles (1170 km) wide, while Pluto itself has a diameter of about 1410 miles (2270 km). The Hubble telescope's Advanced Camera for Surveys observed the two new candidate moons on May 15, "The new satellite candidates are roughly 5,000 times fainter than Pluto, but they really stood out in these Hubble images," said Max Mutchler of the Space Telescope Science Institute and the first team member to identify the satellites. Three days later, Hubble looked at Pluto again. The two objects were still there and appeared to be moving in orbit around Pluto. Illustration from

What Makes a Planet a Planet?
Is Pluto a Planet? What Makes a Planet a Planet? Orbits a star Round Not a star or a moon “Cleared Out” its orbit More information at And at

Is Pluto a Planet? Yes No It has always been considered a planet
Very small Very elliptical orbit Out of plane of ecliptic Same material as Kuiper belt objects Found other “non-planets” that were larger Image based on NASA images, from

New Horizons Pluto-Kuiper Belt Mission
January 2006 Launch! July 2015 – Pluto! – Kuiper Belt Artist's concept of the New Horizons spacecraft as it approaches Pluto and its three moons in summer The craft's miniature cameras, radio science experiment, ultraviolet and infrared spectrometers and space plasma experiments would characterize the global geology and geomorphology of Pluto and large moon Charon, map their surface compositions and temperatures, and examine Pluto's atmosphere in detail. The spacecraft's most prominent design feature is a nearly 7-foot (2.1-meter) dish antenna, through which it will communicate with Earth from as far as 4.7 billion miles (7.5 billion kilometers) away. Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI) Image from

Comets Dirty snowballs - small objects of ice, gas, dust, tiny traces of organic material More information at What does a comet nucleus look like? Formed from the primordial stuff of the solar system, it is thought to resemble a very dirty iceberg. But for active comets, telescopic images only reveal the surrounding cloud of gas and dust, the comet's coma, and the characteristic cometary tails. In 1986, the European spacecraft Giotto encountered the nucleus of Halley's comet as it approached the sun. Data from Giotto's camera was used to generate this enhanced image of the potato shaped nucleus which measures roughly 15 kilometers across. It shows surface features on the dark nucleus against the bright background of the coma as the icy material is vaporized by the Sun's heat. Every 76 years Comet Halley returns to the inner solar system and each time the nucleus sheds about a 6 meter deep layer of its ice and rock into space. This debris composes Halley's tails and leaves an orbiting trail responsible for the Orionids meteor shower. Image from:

Comet Parts Nucleus, Coma
What are comets? Comets have been called “dirty snowballs.” They are small celestial objects, made of ice, gas, dust, and a small amount of organic material, that orbit our Sun. There are about 1000 known comets and more are discovered each year. What are the different parts of a comet? Every comet has a nucleus , a stable, porous central mass of ice, gas, and dust that if often between 1 and 10 kilometers (0.6 to 6 miles) in size. The ice is made of varying amounts of water, carbon dioxide, ammonia, and methane. The dust may contain hydrogen, oxygen, carbon, nitrogen, silica, and some metals. The nucleus may have traces of hydrocarbons. As comets approach our Sun [within about 450 million kilometers (280 million miles)], they heat up and the ice begins to sublimate (change from a solid directly to a gas). The gas (water vapor, carbon monoxide, carbon dioxide, and traces of other substances) and dust forms an “atmosphere” around the nucleus called a “coma.” Material from the coma gets swept into the tail. As comets move close to the Sun, they develop tails of dust and ionized gas. Comets have two main tails, a dust tail and a plasma tail. The dust tail appears whitish-yellow because it is made up of tiny particles — about the size of particles of smoke — that reflect sunlight. Dust tails are typically between 1 and 10 million kilometers (about 600,000 to 6 million miles) long. The plasma tail is often blue because it contains carbon monoxide ions. Solar ultraviolet light breaks down the gas molecules, causing them to glow. Plasma tails can stretch tens of millions of kilometers into space. Rarely, they are as long as 150 million kilometers (almost 100 million miles). A third tail of sodium has been observed on Comet Hale-Bopp. Comets are enveloped in a broad, thin (sparse) hydrogen cloud that can extend for millions of kilometers. This envelope cannot be seen from Earth because its light is absorbed by our atmosphere, but it has been detected by spacecraft. Image from Image credit: K. Jobse, P. Jenniskens and NASA Ames Research Center Nucleus, Coma Dust tail – white, “smoke,” reflects sun. 600,000 to 6 million miles long Ion tail – Solar UV breaks down CO gas, making them glow blue. 10’s of millions of miles

Our Solar System From This is a montage of planetary images taken by spacecraft. Included are (from top to bottom) Mercury, Venus, Earth (and Moon), Mars, Jupiter, Saturn,Uranus and Neptune. The spacecraft responsible for these images are as follows: Mercury was photographed by Mariner 10. Venus was imaged by the Magellan spacecraft's radar. Earth and its Moon were photographed by Galileo. Mars Global Surveyor took the image of Mars. Jupiter was photographed by Cassini as it traveled to Saturn. Saturn, Uranus and Neptune images were taken by the twin Voyager spacecraft. Pluto is not shown. No spacecraft has visited Pluto and it is too small and distant for good photography. The inner planets - Mercury, Venus, Earth, Moon, and Mars - are roughly to scale to each other; the outer planets - Jupiter, Saturn, Uranus, and Neptune - are roughly to scale to each other. But the actual size differences between the inner and outer planets is not to scale. Actual diameters: Sun 1,390,000 km Mercury 4,879 km Venus 12,104 km Earth 12,756 km Moon 3,475 km Mars 6,794 km Jupiter km Saturn 120,536 km Uranus 51,118 km Neptune 49,528 km Pluto 2,390 km Photo montage from:

By the Lunar and Planetary Institute

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By the Lunar and Planetary Institute

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