Planets What do you know about the planets? Planet order plus the asteroid and Kuiper Belts Terrestrial versus jovian planets Terrestrial: rocky with small amounts of ice Earth: only planet with liquid water Jovian: large amount of ammonia and methane ice with a rocky or metallic core Relative planet size Mercury Smallest Densest Craters and lava flows visible Cooled, lacks tectonic activity Thin layer of gases Magnetic field Perhaps ice at poles Extreme temperatures: • Sunny side 950 degrees F • Dark side: -346 degrees F Why are craters rare on Earth and common on the Moon and Mercury? The Earth’s surface is mobile due to processes that produce plate tectonics. Messenger spacecraft Launched 2004 Orbit Mercury, March 18, 2011 Messenger: mission to Mercury Why so dense? Core size and composition? Magnetic field? Ice? If so composition? Extreme temperatures-results? Only 45% of surface has been observed Gravitational Force: the attraction between two masses (remember Newton’s equation?) Your weight is the attraction between the Earth’s mass and yours What would be your weight on Mercury? • More or less? Gavitational pull Earth: 150 pounds Mercury: 57 pounds Venus Slightly smaller than Earth Very hot: 900 degrees F Retrograde rotation (opposite the Earth) Visible in the sky: the morning “star” Venus’ Atmosphere Water and carbon dioxide:97% No liquid water Extreme pressure: 92 X pressure on Earth at sea level (same as .6 miles deep in ocean) Electrical storms within the clouds Sulfuric acid clouds • Can move at 350 KM/hr Greenhouse effect: explanation to why Venus’ surface is so hot 97%CO2 ,3% N Water vapor and Carbon dioxide absorb infrared radiation Venus Tectonic activity Mantle convection Upwelling of mantle material Down-welling of mantle material Basaltic volcanism Radar data enabled Lack of crater scientists to penetrate impacts implying Venus' thick clouds and mobile surface create simulated views of the surface. Exploring Venus Magellan, 1990- 1995 Radar images of Venus’ surface Mars 4th planet, red planet Temperature: -207 degrees to 32 degrees F Atmosphere: 95 % carbon dioxide Water once flowed on surface Sea existed perhaps 5 million years ago Olympus Mons Explored remotely by man Thought most likely to have had life Evidence of water erosion: Valles Marineris Volcanism: largest mountain in the solar system (24x500 KM) Polar ice caps of solid water and Carbon dioxide Comparison to Earth When a rocky planet’s core cools • Magnetic field is lost • Tectonic activity ceases • Atmosphere is lost Mars’ Moons Deimos: 7.5 Phobos miles across Asteroid like Sunrise on Mars, August 26, 2008 Mars The Phoenix Lander arrived May 25. 2008 •Polar region: explore the possibility of life; characterize climate; the geology •May , 2010 transmitting data ceased Picture taken on December 21, 2008 by Mars reconnaissance orbiter ( in orbit since 2001) Jupiter 1000 Earths could fit inside an empty Jupiter Atmosphere: H, He some methane, ammonia Surface pressures so great H gas converted to liquid Metallic hydrogen core 63 Moons Orbit around Sun: 12 Earth years Rotation: 9 hours, 56 minutes Jupiter Pressure breaks up atoms: electrons flow freely, single protons causes Hydrogen to become metallic Magnetic field: 10 x stronger than Earth Great Red Spot 1st photographed by Voyager 1, 1979 Colors are due to warm air rising and cooler air sinking Winds blow counter clockwise around the spot Two times larger than Earth Migrates east and west Galileo spacecraft: launched 1989 crashed 2003 1st to fly past an asteroid Measured Jupiter’s atmosphere Evidence of salt water on Europa, Ganymede, and Callisto Volcanism on Io Purposefully crashed into Jupiter to discover Arrived to Jupiter, 1995 temperatures and pressures Galileo: observed 4 of Jupiter’s 63 moons Ganymede •Europa Io Callisto 6 year mission by the spacecraft Galileo Io •The most volcanically active in solar system •Some volcanoes are hotter than on Earth •100 foot tidal pull on surface Europa •Roughly the size of our moon •More water than Earth •Thin oxygen atmosphere •May have a liquid ocean below icy surface •Cooled, icy crust, brown = non-ice •Internal source of heat Ganymede •Largest moon •Has a magnetic field •Rocky core •Icy outer layer Callisto •Size of Mercury •Cratered surface •Rocky core •Icy mantle Saturn 6th planet Atmosphere:75% Hydrogen, 25% Helium Rocky, metallic interior core; liquid metallic hydrogen Rings are composed of debris held in orbit by Saturn’s gravitational force Some debris is thought to come from volcanism on Saturn’s moon IO Saturn Hubble photograph 1996-2000 Rotates on its axis Orbiting around the Sun Each season is 7 years 30 Earth years to orbit the Sun 10.5 hour rotation Saturn’s Rings Water ice, dust, and gases Particles range in size from pebble to house size 18,000 miles wide .6 mile thick Saturn has 62 Moons Spacecraft Cassini (artist’s interpretation) Since 2004, this spacecraft is collecting data from Saturn and several moons Picture of one moon Titan Largest satellite of Saturn Rocky core, shell of water ice Atmosphere: nitrogen and methane Uranus Blue-green color: crystals of methane Atmosphere: H and He Interiors are composed of methane, ammonia and water Core is composed of rock and metal 84 Earth year orbit 17 hour rotation 98 degree tilt on its axis Voyager 2, 1986 Magnetic field on Uranus is tilted at 58 degrees Uranus has a number of rings Ranging from3-60 miles thick Neptune Magnetic field is tilted at 50 degree 4 X bigger than Earth Orbit: 165 Earth years H, He, water and silicates Solid rocky core 11 satellites Asteroid Gaspra Asteroids Small fragments of rock from the solar system’s formation 19x12x11 kms Red indicates asteroid belt path Asteroids passing Earth Two asteroids pass Earth at about the distance of the Moon One is 32-65 feet in size The other is 20-46 feet in size Dinosaur Extinction 65 million years ago Asteroid impact 190 miles in diameter Sent debris into the atmosphere, blocking solar radiation Reduced plant growth Comets Composed of ice (ammonia, methane, carbon dioxide, and carbon monoxide) Rocky core Tail: solar wind and radiation pressure move ionized gases and dust Sublimation: the change in state from solid to gas without passing through the liquid stage Kuiper Belt Comets orbit the Sun in the same plane as the planets Meteoroids Less than a meter Debris from asteroid belt, interplanetary material or the moon Friction from the meteoroids and air heats both and we see a “shooting star” Next meteor showers: August 12-13, 60 meteors/hour New Information Kepler-11 star, 2000 light years away Appears to have rocky planets Most complete planetary system This concludes the astronomy portion of the class.
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