Remnants of Rock and Ice

1. Remnants of Rock and Ice Remnants of Rock and Ice: Asteroids, Comets, and Pluto

2. Remnants from Birth • Comets, Asteroids and Meteorites carry the history of our solar system encoded in their compositions, locations, and numbers. • Asteroid: • a rocky leftover planetesimal orbiting the Sun. • Comet: • an icy leftover planetesimal orbiting the Sun-regardless of its size or whether or not it has a tail.

3. Meteor: • a flash of light in the sky caused by a particle entering the atmosphere, whether the particle comes from an asteroid or a comet. • Meteorite: • any piece of rock that fell to the ground from the sky, whether from an asteroid, a comet, or even another planet.

4. Asteroids

5. The main Asteroid Belt lies between 2.2 and 3.3 AU from the Sun. • Origin and Evolution of the Asteroid belt: • The Asteroid belt probably formed as a result of orbital resonance. Resonance occurs whenever one object’s orbital period is a simple ratio of another object’s period. • These resonances with Jupiter probably prevented a planet from ever forming in the region of the Asteroid Belt.

6. Another effect of the resonance is to form gaps in the orbits of the Asteroids as they orbit the Sun. • These are called the Kirkwood Gaps.

7. The Kirkwood Gaps

8. Asteroids are recognizable in telescope images because they move relative to the stars in just a short time.

9. See SFA Observatory SFA Observatory Asteroid Discoveries

10. Gaspra (16 km across) Galileo Ida(53 km) and its tiny moon Galileo Mathide(59 km) NEAR Eros (40 km) NEAR

11. Meteorites • Primitive Meteorites: Most primitive meteorites are composed of rocky minerals with an important difference from Earth rocks. • The Primitive Meteorites are our best source of information about conditions in the solar nebula.

12. Processed Meteorites • A smaller group of meteorites appears to have undergone substantial change since the formation of the solar system. • These “Processed Meteorites” apparently were once part of a larger object that modified the original material into another form.

13. Carbon-rich primitive meteorite Primitive Stony primitive meteorite Differential iron meteorite Differential stony meteorite Processed

14. Origin of Meteorites • Carbon –rich meteorites came from the outer portion of the asteroid belt. (> 3AU) • Carbon – poor meteorites formed in the inner warmer part of the asteroid belt. • The processed meteorites have compositions similar to the cores, mantles, or crusts of the terrestrial worlds. These are fragments of the terrestrial worlds.

15. Processed meteorites with basaltic compositions must have come from lava flows.

16. Comets • Icy Planetesimals that have been left over from the formation of the Solar System. “Sun Grazing” comet observed by The Solar and Heliospheric Observatory (SOHO).

17. Anatomy of a Comet

19. Comets exist as bare nuclei over most of their orbits and grow a coma and tails only when they approach the Sun

21. The Kuiper Belt and the Oort Cloud

22. Pluto • Pluto was discovered in 1930 by an American Astronomer named Clyde Tombaugh. • Pluto has long been seen to be a misfit among the planets, fitting into neither the terrestrail nor the jovian category. • It has a 248 year orbit that is unusually elliptical and significantly tilted relative to the ecliptic. • Pluto has a moon – Charon.

24. Cosmic Collisions • The numbers of small bodies orbiting the solar system have diminished significantly since the days of early bombardment, when most impact craters were formed. • However, there are still plenty of fragments left and collisions between these fragments and the planets still occur on occasion.

25. Comet Shoemaker-Levy 9

26. Comet Shoemaker-Levy 9

27. The End.

28. Comet Shoemaker-Levy 9 • Was shatter by Jupiter’s gravity in 1992. • All pieces hit Jupiter in the summer of 1994 leaving dark impact scars.

29. Images obtained by Dan Bruton in 1994

30. Meteor Shower

34. Minor Body Comparisons Property ___Asteroids _________ Comets Orbit Shape Circular to Highly elliptical elliptical Size 0.5 km to 625 km Nucleus 1 to 10 km Composition Iron or Rocky Ice and Rock Named? Named by their Named after their discoverers discoverers

35. Earth Impacts and Near Misses • Arizona Meteor Crater • measures 1 mile across • from an impact 50,000 years ago • by a 50 meter meteoroid

36. Tunguska Event • in 1908 • an asteroid broke up in our atmosphere • leveled trees for some 30 kilometers

37. Frequency of Impacts versus impactor size & Effects

38. Chicxulub Event /cheek-shoo-loob/ • 65,000,000 years ago • 10 kilometer asteroid • is thought to have caused a mass extinction of dinosaurs

40. The End... Live long and prosper.