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Transcript
Plan for this week • The jovian planets • 5 major moons • Comets, asteroids, and Earth impacts The jovian planets The jovian planets • All very large • All rotate very fast • All made mostly of gaseous material Jupiter Jupiter The Great Red Spot Jupiter Saturn Saturn Uranus Neptune Neptune Data for the jovian planets Jovian interiors • At the center, a dense core of rock, metal, and hydrogen compounds • Around the core is gaseous molecules • Jupiter and Saturn • Mostly hydrogen • Includes states of matter not found on Earth • Uranus and Neptune • Water, methane, hydrogen The jovian moons • Some of the jovian moons are far more interesting than the planets themselves • There are more than 90 total • They come in all sizes Small jovian moons Medium sized jovian moons Large jovian moons The jovian moons • The largest moons in the solar system are: 1. Ganymede (Jupiter) 2. Titan (Saturn) 3. Callisto (Jupiter) 4. Io (Jupiter) 5. ‘The Moon’ (Earth) 6. Europa (Jupiter) 7. Triton (Neptune) The Galilean moons The Galilean moons • The four largest moons of Jupiter • Discovered by Galileo in the early 1600s • Very important historically • Proved that everything does not go around the Earth • Got Galileo in a lot of trouble! The Galilean moons • Io • The closest one to Jupiter • Size: • Larger than Pluto • Smaller than Mercury • Experiences very strong tidal forces Tidal forces Io (Other moons) Jupiter The Galilean moons • Io is the most geologically active place in the solar system! • Volcanoes continuously erupting • Not a single impact crater on its surface Io The Galilean moons • Europa • The next moon out from Jupiter • Size: • Larger than Pluto • Smaller than the Moon or Mercury • Also experiences tidal forces • Surface is entirely covered with ice • May have a water ocean under the ice • A possible place for life? Europa Europa The Galilean moons • Ganymede • The largest moon in the solar system • Larger than Pluto and Mercury! • (That’s all you need to know about it…) Ganymede The Galilean moons • Callisto • The fourth one (just for completeness) Callisto Saturn’s moons • Titan • Size: • The 2nd largest moon in the solar system • Larger than both Pluto and Mercury • The only moon in the solar system with a substantial atmosphere • Mostly nitrogen (like Earth!) • Atmospheric pressure = 1.5 x Earth’s • Wouldn’t need a space suit! (cold though…) Titan Pluto • • • • • The most distant planet - if it’s a planet! Distance: 30 - 50 AU (40 average) Orbit = 248 years Rotation = 6.4 Earth-days Has one moon: Charon • About half the size of Pluto Pluto & Charon Pluto & Charon Planetary rings • All jovian planets have ring systems • All are made of small pieces of debris • Probably unformed moons, or moons that were broken apart by the planet’s gravity Saturn’s rings • Small chunks of ice (mostly) • Incredibly thin • A single sheet of paper 3 football fields across! • Made of many ‘ringlets’ Asteroids • Chunks of rock and metal • Mostly in the asteroid belt - but not all of ‘em! • Earth crossing asteroids • Have orbits that bring them near Earth’s orbit Comets • Chunks of ice, rock, & metal (‘dirty snowballs’) • Today in two locations: • The Kuiper belt • Beyond Neptune’s orbit • ~ 30 - 100 AU out • In the disk of the solar system • The Oort cloud • A sphere way, way beyond Neptune • ~ 50,000 AU out A comet nucleus Comets • If a comet ‘falls’ towards the Sun: • It begins to sublimate (solid --> gas) • Develops a tail • This tail always points away from the Sun The Sun