1. Asteroids & Meteorites 20 October 2014

2. Asteroids Apollo Trojans

3. Asteroid Belt as viewed from Above Over 100,000 objects greater than 10 km. now identified in the Main Belt Total mass less than 1% of moon’s mass Over 100 NEAs greater than 1 km. across are being tracked; probably part of a population of about 2000 Kirkwood gap (and others) occur in the belt where there are orbital resonances with Jupiter Asteroids classified by ‘spectral group

4. Kirkwood Gaps

5. S Asteroids (‘silicaceous’) 951 Gaspra433 Eros (true color)Ida (and Dactyl) 19 x 12 x 11 km 33 x 13 x13 km58 x 23 km (1km) Galileo flyby, 199 NEAR orbit/landingGalileo flyby, 1993 Grooves, curved near-Earth asteroid, member of Koronis depressions, ridges space weatheringfamily, first ID of (Phobos-like) effects documentedasteroid ‘moons’

6. C Asteroids (‘carbonaceous’) 253 Mathilde; 66 x 48 x 46 km, visited by NEAR Shoemaker Surface as dark as charcoal; typical outer belt asteroid

7. Ida and Dactyl

8. Itokawa

9. Hyabusa samples Itokawa

10. Hyabusa Returns June 2010

11. Steins 2008

12. Toutatis

13. Vesta, Ceres, Moon

14. Dawn Mission at Vesta

16. Vesta Craters

17. Asteroids Summary Solid objects mostly in a belt between Mars and Jupiter Small bodies much more common than larger ones Classes similar to meteorites: Stony (S), Carbonaceous (C), Metallic (M) Bodies and belts shaped by collisions, resonances Source of meteorites

19. Meteorites

20. Chondrite

21. Achondrite

22. Martian

23. Asteroid Belt as viewed from Above Over 100,000 objects greater than 10 km. now identified in the Main Belt Total mass less than 1% of moon’s mass Over 100 NEAs greater than 1 km. across are being tracked; probably part of a population of about 2000 Kirkwood gap (and others) occur in the belt where there are orbital resonances with Jupiter Asteroids classified by ‘spectral group

24. S Asteroids (‘silicaceous’) 951 Gaspra433 Eros (true color)Ida (and Dactyl) 19 x 12 x 11 km 33 x 13 x13 km58 x 23 km (1km) Galileo flyby, 199 NEAR orbit/landingGalileo flyby, 1993 Grooves, curved near-Earth asteroid, member of Koronis depressions, ridges space weatheringfamily, first ID of (Phobos-like) effects documentedasteroid ‘moons’

25. C Asteroids (‘carbonaceous’) 253 Mathilde; 66 x 48 x 46 km, visited by NEAR Shoemaker Surface as dark as charcoal; typical outer belt asteroid

26. Chixulub, Yucatan penninsula, Mexico Gravity map of buried structure 180 miles across; 65 millions years old Identified in early 1990s with seismic data, after 10 year ‘search’

27. Tunguska, Siberia, June 30, 1908 Black and white photos taken during field expedition in 1927; color photo taken in 1990

28. Jackson Hole Fireball, August 10, 1972

29. Potentially Hazardous Asteroid Threat Size-frequency diagram for impacting objects ~100 tons of meteroritic dust falls each day 50 m impactor once per 1000 yr (local effects) 500 m impactor once per million years (regional effects) 5 km. impactor once per 100 million years (global effects)

30. Hoba Iron 3m x 2m x 1m; 60+ tons Found 1920, Namibia No crater, classified ataxite

31. Ordinary Chondrites (S Asteroids?)

32. Three Views of Vesta Hubble image, model and color-shaded topography Largest member of V class of asteroids (vestoids) Spectral variations consistent with HEDs

33. What were the processes and products in the early Solar System ( Meteoritics, 2004) Impact features on all planetary surfaces; planets formed by accretion of planetesimals from a turbulent solar nebula Much mixing of components; completed in 5-10 million years ‘Residual’ debris forms asteroid belt; Kuiper belt, Oort cloud

34. Meteor showers Time exposure image, tracking stellar motion Stars stay still, meteorites make trails

35. The Peekskill (NY) Fireball

36. P Jenniskens et al. Nature 458, 485-488 (2009) Macroscopic features of the Almahata Sitta meteorite.

37. Chondrites Rocky, inhomogeneous, contain round “chondrules” Microscope image

38. Iron meteorites: from core of differentiated asteroids

39. Stony-Iron meteorites - the prettiest Crystals of olivene (a rock mineral) embedded in iron From boundary between core and mantle of large asteroids?

43. The main points: Meteorites Each year the Earth sweeps up ~80,000 tons of extraterrestrial matter Some are identifiable pieces of the Moon, Mars, or Vesta; most are pieces of asteroids Meteorites were broken off their parent bodies 10’s to 100’s of million years ago (recently compared to age of Solar System) Oldest meteorites (chondrites) contain interstellar dust, tiny diamonds made in supernova explosions, organic molecules and amino acids (building blocks of life) Direct insight into pre-solar system matter, solar system formation