Venus

Venus Diameter: 12,10 4 km, 0.95 Earth Diameters Planetary Mass: 4.86x10 24 kg, 0.82 Earth masses Density:5.24 g/cm 3 Avg. Dist. from Sun: 108 million km, AU Closest dist. to Earth: 38 million km Number of moons: 0 Magnetic field: None Average temperature: 460 o C on both the day and night sides Atmospheric composition: 96.5% Carbon Dioxide (CO 2 ), 3.5% Nitrogen (N 2 ) Venus Facts

Venus Facts – cont. Axial tilt:177.3 o, which means that it is rotating in space upside down! It’s axis is only 2.7 o tilted from ecliptic, which isn’t enough to cause seasons. Length of Day: 243 Earth days backwards (clockwise) Length of Year: 225 Earth days

Name Origin Named after the Roman goddess of love and beauty. The planet was named Venus because it was the brightest of the planets known to the ancients. Commonly called the “evening star” or the “morning star” Much brighter than any star. Originally the Greeks thought Venus was two different planets.

Peculiar Rotation Rotation is retrograde: rotation is opposite of the direction of orbital motion –Orbit motion around the Sun: counterclockwise –Venus’s rotation on its axis: clockwise –Planets and satellites have prograde rotation except Venus, Uranus and Pluto

Appearance of Venus Simple telescopes can detect that Venus goes through phases like the Moon It can often seen in the eastern sky at dawn or in the western sky after sunset Surface is always obscured by a very dense cloud cover Clouds reflect 70% of the sunlight, causing its brightness Enhanced picture of Venus shot through a violet filter by the Galileo spacecraft

Phases of Venus Venus appears to go through phases like the moon Different from the moon because its distance from us changes drastically

Venus Interior Internal composition is probably similar to Earth. It is possible that the core is liquid iron. Core has less mass than Earth’s (only 23% of total planet). Based on size, Venus should be heavier We do not know if the core contains less iron or if it is smaller than Earth’s.

Interior The presence of volcanoes suggests a molten interior Venus has no planet-wide magnetic field, possibly due to the fact that Venus rotates too slowly. Venus has no plate tectonics, possibly due to that the crust is too hot and soft to move in rigid plates

Venus Atmosphere Atmosphere of mainly CO 2 Clouds of sulfuric acid No water Crushing atmospheric pressure of about 90 atm High-velocity winds in upper atmosphere but low-velocity surface winds (we don’t know why) High surface temperatures from “Greenhouse Effect” Slow surface erosion rate

High clouds with a clear CO 2 atmosphere below. Much warmer atmosphere near the planet ’ s surface than Earth ’ s, but colder at high altitudes.

The sunlight that is able to pass through the clouds warms the surface. The surface then re-radiates heat upwards. The heat becomes trapped below the clouds. The result is a much higher surface temperature than would be present without the blanketing effect of the atmosphere. Greenhouse Effect

Carbon dioxide cycle on Earth keeps us from being like Venus But this cycle would not work if there’s no liquid water!

Venus Atmospheric Missions Mariner 10 – Fly-by in 1973 on its way to Mercury Pioneer Venus – Five probes in 1978 Vega 1 and 2 – Two probes in 1985 Galileo – Fly-by in 1990 Europe’s Venus Express Messenger – Made fly-bys in 2006 and 2007 on its way to Mercury

Pioneer Venus 1978 Venus Atmosphere Venus Topography Orbiter

Visible versus Radar Orange colors in radar images are not “real”. Colors have been enhanced to show surface features more clearly

Venus Surface Surface rocks are basaltic (similar to our ocean floor). Dense atmosphere prevents studying the surface from orbit. Craters and “pristine” appearance suggest young surface. No plate tectonics No true continents or ocean basins We do not know the range of ages of the rocks on the surface We do not know how the surface changed with time

Surface The surface of Venus is surprisingly flat, with only a few major highlands and several large volcanoes The surface of Venus shows no evidence of plate tectonics (or the motion of large crustal plates) –No long chain of volcanic mountains

Venus Surface Features Planitia: Low plains Terra: Extensive land masses Planum: Plateaus Corona: Ovoid-shaped volcanic features Volcanic craters: numerous Impact Craters: about 1000, randomly distributed

Volcanic Structures

Shield Volcanoes Sif Mons Shield Volcano Low-sloping volcanoes formed from repeated eruptions of low-viscosity lava

Impact Craters Radar images from Magellan Bright regions: high radar reflectivity – “rough” Dark regions: low reflectivity – “smooth” Yablochkina impact crater

The radar bright outflow associated with the 90 km crater stretches over 600 km to the east. Addams Impact Crater

The channel is about 2 km wide and shows branches and islands along its length. The image shown here is about 50 km wide. Probably low viscosity, high temperature lava. Lava Channel

Flattened tops and steep edges. Probably formed by the eruption of thick lava. High atmospheric pressure likely caused the flattened tops The largest dome is 62 km in diameter. Volcanic “Pancake" Domes

Volcanic feature Dome with a large volcanic vent (caldera) Surrounded by radial spurs that look like legs. “Tick”

Magellan image of a nova. A pattern of hills and valleys that radiate outward from a single point. This nova is about 250 km in diameter Nova

The Maxwell Montes are the highest mountains on Venus rising up to 11 km above the surface. Maxwell Montes

Venus Surface Studies Mariner 2: First planetary mission in 1972 Pioneer Venus:Topography and atmospheric probes in 1978 Veneras 8 – 14: Surface landers from Veneras 15 & 16: Orbital radars, 1984 Magellan: Orbital radar images, topography and gravity data, Europe’s Venus Express: 2006

Venus Surface Studies Orbital Missions: Pioneer Venus, Magellan. Surface Missions: Vega and Venera Future studies: NASA and the ESA are looking into the possibility of sending a lander to Venus to collect rock samples and return them to Earth for analysis New generation of surface measurements by landed spacecraft. Still in the proposal stage

Proposed Venus Sample Return mission 6 years round trip

Venera Lander Images of Venus Venera min. surface operation Venera min. surface operation Venera hrs 7 min. surface operation Venera min. surface operation

Magellan The primary objective of the mission was to map the surface the surface features of Venus 98% of the surface was imaged at high resolutions

Magellan Volcanic "pancake" domes in Tinatin Planitia, Venus At 280 km diameter, Mead Crater is the largest impact crater on Venus. Computer generated 3-dimensional perspective view of the "crater farm" 3-dimensional image of Sapas Mons a 1.5 km high volcano

1.Was Venus ever a habitable planet? 2.Did Venus possess abundant surface water in its early history? 3.What is the nature of weathering on the Venusian surface? 4.What has been the composition and evolutionary history of the Venusian atmosphere? 5.What has been the volcanic history of Venus over time? 6.Did Venus ever have plate tectonics? 7.What has been the cratering rate on Venus over time? 8. What are the ages of different rocks and features on Venus’ surface? 9. What is the overall chemical composition of Venus and how does it compare to other planetary bodies in the solar system? 10. What are the geophysical properties (heat flow, seismic activity, etc.) of the interior and what do they reveal about the internal structure of Venus? Top Ten Questions about Venus