An overview of the Planets

*******Add to your notes: Ecliptic Plane - plane of the Earth's orbit around the Sun. Most objects in the solar system orbit in roughly this plane and in the same direction around the Sun as the Earth.

The Terrestrial planets (Inner Planets) Mercury Venus Earth Mars

Characteristics of terrestrial planets Smaller than gas giants Smaller than gas giants Little or no atmosphere Little or no atmosphere Rocky terrain Rocky terrain Made of heavier elements = high density Made of heavier elements = high density Few or no moons Few or no moons

Mercury Closest to the Sun Closest to the Sun Smallest planet Smallest planet No atmosphere or moons No atmosphere or moons One-third size of Earth One-third size of Earth Solid and is covered with craters. Solid and is covered with craters. Shortest revolution (88 days) Shortest revolution (88 days) 427 o C to -173 o C 427 o C to -173 o C

Venus Venus is the sixth largest planet. It’s about three- fourths the size of Earth. Venus is the sixth largest planet. It’s about three- fourths the size of Earth. Size and density similar to Earth Size and density similar to Earth The surface is rocky. The surface is rocky. No moons No moons Thick atmosphere Thick atmosphere Hottest planet = 464 o C Hottest planet = 464 o C **Rotates Clockwise **Rotates Clockwise

Venus Greenhouse effect gone crazy! Greenhouse effect gone crazy! The atmosphere hides the surface and traps the heat. The atmosphere hides the surface and traps the heat. Atmosphere pressure is high; mostly CO 2 with sulfuric acid clouds Atmosphere pressure is high; mostly CO 2 with sulfuric acid clouds

Earth

Earth 5th largest planet and 3 rd from the Sun. 5th largest planet and 3 rd from the Sun. Liquid water covers 71% of the surface. Only planet in solar system with liquid water and life! Liquid water covers 71% of the surface. Only planet in solar system with liquid water and life! One moon. One moon. Only geologically active planet Only geologically active planet

Moon

Mars 4 th planet from the Sun 4 th planet from the Sun Very thin atmosphere (mostly CO 2 ) compared to Earth and Venus Very thin atmosphere (mostly CO 2 ) compared to Earth and Venus “Red Planet” due to high iron oxide content in surface (rust) “Red Planet” due to high iron oxide content in surface (rust) Polar ice caps of “dry ice” Polar ice caps of “dry ice” Has the largest volcano called Olympus Mons Has the largest volcano called Olympus Mons

Mars has two small moons. PhobosDeimos

Exploration to Mars Pathfinder 1997 Spirit Rover 2004

Gas Giants (Outer Planets) Jupiter Jupiter Saturn Saturn Uranus Uranus Neptune Neptune

Characteristics of Gas Giants Larger than terrestrial planets Larger than terrestrial planets Ring systems Ring systems Many moons Many moons Made of lightweight elements = low density Made of lightweight elements = low density Large atmospheres Large atmospheres **Widely Spaced **Widely Spaced

Jupiter

Jupiter 5 th planet from the Sun 5 th planet from the Sun Largest planet in solar system Largest planet in solar system 70% of all planetary mass! 70% of all planetary mass! Atmosphere mostly H 2 and He Atmosphere mostly H 2 and He Also has rings (but not as easy to see as Saturn!) Also has rings (but not as easy to see as Saturn!) Has the MOST satellites (63 total) Has the MOST satellites (63 total) **Has the strongest Gravity **Has the strongest Gravity

Comet impact w/ Jupiter 1994 – Comet Shoemaker-Levy

Jupiter’s Red Spot The Great Red Spot, a huge storm of swirling gas that has lasted for hundreds of years. The Great Red Spot, a huge storm of swirling gas that has lasted for hundreds of years. Jupiter does not have a solid surface. The planet is a ball of liquid surrounded by gas. Jupiter does not have a solid surface. The planet is a ball of liquid surrounded by gas.

Moons of Jupiter Jupiter has four large Galilean moons, and 62 total moons! Jupiter has four large Galilean moons, and 62 total moons! Galilean moons: Io, Europa, Ganymede, Callisto Galilean moons: Io, Europa, Ganymede, Callisto The 4 large Galilean moons were first observed by Galileo in The 4 large Galilean moons were first observed by Galileo in 1610.

Io Third largest of Jupiter’s moons. Third largest of Jupiter’s moons. Io has hundreds of volcanic calderas. Some of the volcanoes are active. Io has hundreds of volcanic calderas. Some of the volcanoes are active.

Europa Fourth largest. Fourth largest. Slightly smaller than Earth’s moon. Slightly smaller than Earth’s moon. The surface strongly resembles images of sea ice on Earth. May be a liquid water sea under the crust. The surface strongly resembles images of sea ice on Earth. May be a liquid water sea under the crust. One of the 5 known moons in the solar system to have an atmosphere. One of the 5 known moons in the solar system to have an atmosphere.

Ganymede Largest of Jupiter’s known satellites. Largest of Jupiter’s known satellites. Ganymede has extensive cratering and an icy crust. Ganymede has extensive cratering and an icy crust.

Callisto Second largest of Jupiter’s satellites. Second largest of Jupiter’s satellites. Oldest, most cratered surface of any body yet observed in the solar system. Oldest, most cratered surface of any body yet observed in the solar system.

Saturn

Saturn Saturn is the second largest planet and the sixth from the Sun. Saturn is the second largest planet and the sixth from the Sun. Saturn is made of materials that are less dense than water. If you could fit Saturn in a lake, it would float (because of the low density)! Saturn is made of materials that are less dense than water. If you could fit Saturn in a lake, it would float (because of the low density)! Atmosphere is mostly H 2 and He Atmosphere is mostly H 2 and He Titan is main moon Titan is main moon Elaborate ring system! Elaborate ring system!

Rings of Saturn Saturn’s rings are not solid; they are composed of small countless particles. Saturn’s rings are not solid; they are composed of small countless particles. The rings are very thin. Though they’re 250,000km or more in diameter, they’re less than one kilometer thick. The rings are very thin. Though they’re 250,000km or more in diameter, they’re less than one kilometer thick.

Uranus

Uranus 7 th planet from the Sun 7 th planet from the Sun Atmosphere mostly H 2 He and CH 3 (methane) Atmosphere mostly H 2 He and CH 3 (methane) Blue-green because of the methane in its atmosphere. Blue-green because of the methane in its atmosphere. Plane of rotation is almost on its side Plane of rotation is almost on its side Also has rings. Also has rings. 27 moons. Largest is Miranda 27 moons. Largest is Miranda ***Rotates clockwise ***Rotates clockwise

Neptune

Neptune Neptune is the fourth largest planet and the eight from the Sun. Neptune is the fourth largest planet and the eight from the Sun to 1999, Neptune was the ninth planet to 1999, Neptune was the ninth planet. Atm mostly H 2, He, CH 3 Atm mostly H 2, He, CH 3 Like Uranus, the methane gives Neptune its color. Like Uranus, the methane gives Neptune its color. 13 moons. Largest moon is Triton 13 moons. Largest moon is Triton Has rings also. Has rings also.

Pluto

Pluto No longer considered a planet! No longer considered a planet! Very small with a small atmosphere— which is mostly N 2 and CH 3 Very small with a small atmosphere— which is mostly N 2 and CH 3 Low density; half ice and half rock Low density; half ice and half rock 50 AU from Sun = 4,560,000,000 miles! 50 AU from Sun = 4,560,000,000 miles! Once a moon of Neptune? Or a comet? Once a moon of Neptune? Or a comet? Pluto and its moon, Charon, are similar in size. Two other moons have been found. Pluto and its moon, Charon, are similar in size. Two other moons have been found.

Neptune’s and Pluto’s orbit

Why is it not a planet anymore? In August 2006, the International Astronomical Union decided on a new definition for a planet. Pluto is no longer a planet! It is now referred to as a dwarf planet (sometimes referred to as minor planets)! In August 2006, the International Astronomical Union decided on a new definition for a planet. Pluto is no longer a planet! It is now referred to as a dwarf planet (sometimes referred to as minor planets)! To be a planet it must be in orbit around the Sun, have sufficient mass (so it is nearly round), and "cleared the neighborhood" around its orbit. To be a planet it must be in orbit around the Sun, have sufficient mass (so it is nearly round), and "cleared the neighborhood" around its orbit.

Other parts of the Solar System Kuiper Belt: Only confirmed about 10 years ago! An icy collection of objects (including Pluto) that is about AU from the Sun. Short-period comets take less than 200 yrs to orbit the Sun. Kuiper Belt: Only confirmed about 10 years ago! An icy collection of objects (including Pluto) that is about AU from the Sun. Short-period comets take less than 200 yrs to orbit the Sun. Oort Cloud: Spherical shell of billions of icy bodies near the edge of the Solar System. Found between 5,000 and 100,000 AU! Long-period comets and are observed only once. Oort Cloud: Spherical shell of billions of icy bodies near the edge of the Solar System. Found between 5,000 and 100,000 AU! Long-period comets and are observed only once.