1. Spacecraft Study of Asteroids
DrBill (20361) Romanishin
U. Of Oklahoma and Oklahoma City Astronomy Club

2. Brief Intro to Asteroids
Most orbit in main asteroid belt between Mars and Jupiter
Some cross paths with Earth (ALWAYS
Wear a helmet when outdoors!)
Range in size from pebbles to 1000 km across (about size of Texas)
As of yesterday 257,455 asteroids have numbers (good orbits), another 282,913

3. have lesser known orbits- so, over Half a Million asteroids are cataloged! We think there are ~1.5 million with diameters greater than 1 km (0.6 mile) + “billions and billions” smaller ones *But* all asteroids together have mass only ~ Mass of Earth Rich dynamical structure – interactions with mighty Jupiter

6. What do asteroids look like?
From groundbased telescope, just a dot of light, like a star , but it MOVES
We have closeup images of only a handful of asteroids from spacecraft flybys
Sometimes, pieces of asteroids hit the Earth- these are asteroids you can hold in your hand

9. Origin and Composition
Asteroids probably remains of a “failed planet” – formation stopped by gravity of forming Jupiter (?)
What are they made of?
Have good idea from meteorites
Similar elements to stuff in Earth

10. Stony or Metallic 1000s of meteorites in collections around world
Bewildering array of detailed
compositions
But to simplify, meteorites are
Stony or
Metallic

11. Stony meteorites have minerals that you would hear about in any intro geology course (olivines, pyroxenes etc) One difference from Earth rocks are the chondrules – BB sized bits of minerals that are OLDEST THINGS WE CAN ACCURATELY DATE Chondrules 4560 Myr old- getting to point we can say “this chondrule 10 Myr older”

13. Another un-terrestrial feature is existence of metallic (iron/nickel) meteorites Iron a common Earth element, but PURE iron is very rare- most iron oxidized on Earth Iron meteorites show Widmanstatten pattern Effect of Slow Cooling of liquid iron

15. Pure iron from core of Differentated body
Some large asteroids must have formed quickly, melted and differentiated, but then were destroyed by collisions releasing iron meteorites
Didn’t quite have time to form one big
(planet sized) body before Jupiter formed
and disrupted the formation process

16. First closeup images
Prior to 1991, asteroids were dots of light Lightcurves gave some info on overall shapes First asteroid closeup from Galileo, a space probe on its way to Jupiter Galileo- launch 1989 Orbited and studied Juipter and moons from

17. 951 Gaspra from Galileo

18. (243) Ida and companion Dactyl from Galileo 1993

20. Galileo images showed: (1) cratering a very important process shaping asteroids (2) binary asteroids did exist

21. NEAR Shoemaker
(Near Earth Asteroid Rendezvous) Launch 1996 Flew by 253 Mathilde in 1997 Entered orbit around 433 Eros on 14 Feb 2000 “Landed” on Eros 12 Feb 2001

24. movie

25. Eros regolith

27. Eugene M. Shoemaker
Meteor Crater Apollo SL9 He got to the Moon.

28. Hayabusa
Japanese effort to land on asteroid and return sample of surface Launch 2003 to Itokawa “minilander” robot failed Main craft “bump landed” and tried to collect surface particles Capsule returned to Earth – Landed in Australia in June 2010 November 2010 “some particles in capsule definitely from Itokawa”- Stay Tuned

36. Rosetta One its way to comet 67P/Churimov-Gerasimenko
Flew by 2 asteroids:
2867 Steins in 2008
21 Lutetia in 2010

40. Comets and Asteroids visited by spacecraft
Emily Lakdawalla planetarysociety.org

41. Coming Attractions- Dawn
Dawn Extended visits to 2 asteroids Launch 2007 Currently nearing Vesta (Jul Jul 2012) On to Ceres (Feb Jul 2015)

49. 3D shapes from Lightcurves