Asteroids Asteroid Belt Between Mars and Jupiter there
Asteroids
Asteroid Belt • Between Mars and Jupiter there a number of objects. – Much smaller than a planet • The small amount of light led them to be named asteroids. Ø Jupiter’s gravity keeps asteroids from growing too large. Mars’ orbit Main belt Jupiter’s orbit
Minor Planets • 26 asteroids have diameters greater than 200 km. – Largest: Ceres, 933 km • Large asteroids show some differentiation into layers like a planet, including lava flows.
Types of Asteroids C-type v 75% of asteroids v extremely dark (albedo 0. 03) v oldest material, carbon and other minerals. S-type v 17% of asteroids v bright (albedo 0. 10 to 0. 22) v iron mixed with silicate rock. M-type v 8% of asteroids v bright (albedo 0. 10 to 0. 18) v pure iron with nickel and other metals.
Mathilde • Mathilde is a main-belt asteroid (66 km long). – Dark type C – Craters with little splash NEAR/Mathilde
Trojan Asteroids • The law of gravity permits an orbit around the sun exactly 60º ahead of and behind Jupiter, called Lagrange points. – Asteroids collect there – Several hundred Trojan asteroids locked to Jupiter L 4 Trojans Jupiter L 5 Trojans
Near Earth Asteroids • Asteroids nudged by Jupiter’s gravity head into the inner solar system. • Many of these now have orbits that cross the orbit of Earth.
Eros • Eros is a near-earth asteroid (30 km long). – Bright type S – Impact boulders on its surface • The NEAR spacecraft also visited here, and safely touched down on the surface. NEAR/Eros
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