Asteroids and Meteorites

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Isabella Miller
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1 Asteroids and Meteorites

Asteroid Facts Asteroids are rocky le2overs of planet forma7on. Asteroids are cratered and not round. The largest is Ceres, diameter ~1000 kilometers.

2 Asteroid Facts Asteroids are rocky le2overs of planet forma7on. Asteroids are cratered and not round. The largest is Ceres, diameter ~1000 kilometers. 150,000 in catalogs, and probably over a million with diameter >1 kilometer. Small asteroids are more common than large asteroids. All the asteroids in the solar system wouldn t add up to even a small terrestrial planet.

3 Asteroids with Moons Some large asteroids have their own moon. Asteroid Ida has a 7ny moon named Dactyl.

4 Asteroid Orbits Most asteroids orbit in the asteroid belt between Mars and Jupiter. Trojan asteroids follow Jupiter s orbit. Orbits of near- Earth asteroids cross Earth s orbit.

6 Origin of Asteroid Belt Rocky planetesimals between Mars and Jupiter did not accrete into a planet. Jupiter s gravity, through influence of orbital resonances, s7rred up asteroid orbits and prevented their accre7on into a planet.

7 If you discover an asteroid and track its orbit, you get to name it.

8 Meteorites

9 Meteor Terminology Meteorite: a rock from space that falls through Earth s atmosphere Meteor: the bright trail le2 by a meteorite Falling star = meteor Bolide = a really bright meteor

10 Near Earth Asteroids

11 Meteorite Impact Chicago, March 26, 2003

13 Meteorite Types 1) Primi7ve: unchanged in composi7on since they first formed 4.6 billion years ago 2) Processed: younger; have experienced processes like volcanism or differen7a7on 3) Stony Meteorites; Iron Meteorites

14 Stony Meteorite

15 Iron Meteorite

16 Meteorites from Moon and Mars A few meteorites arrive from the Moon and Mars. Composi7on differs from the asteroid fragments. A cheap (but slow) way to acquire Moon rocks and Mars rocks

17 Collec7ng meteorites in Antarc7ca and other places Robert A Haag has flown ultralight plane over Sonoran Desert Looking for black rocks. Finding meteorites in Antarc7ca is big science business.

18 Meteor Showers Many meteors seeming to come in along radiants

19 Meteors in a meteor shower appear to emanate from the same area of sky because of Earth s mo7on through space.

23 Glassy fragments, Probably formed by impacts Tek7tes

24 Impacts and Mass Ex7nc7ons

25 K- T Boundary K- T Boundary (Cretaceous- Ter7ary) There is an excess of iridium everywhere on the Earth at the layer which was laid down 65 million years ago. Iridium is rare on Earth, but is common in certain types of meteorites. 65 million years ago, there was a mass ex7nc7on, 75-80% of all species died suddenly, including the dinosaurs, pterosaurs, ammonites and most marine rep7les A large impact killed the dinosaurs

ago, when over 96% of the species alive at the 7me became ex7nct.

26 Other Mass Ex7nc7ons At least 5 other mass ex7nc7ons in the fossil record Largest was at the end of the Permian Period, 245 million years ago, when over 96% of the species alive at the 7me became ex7nct. There is no evidence for a meteor impact causing any of the other mass ex7nc7ons

27 Should we worry? Es7mate that the odds that you will die from an impact of an asteroid in any given year is about 1 in 20,000 NASA has funded several searches for NEAs Cause Odds of Dying in the US Motor Vehicle accident 1 in 100 Murder 1 in 300 Fire 1 in 800 Firearms Accident 1 in 2,500 Electrocu7on 1 in 5,000 Asteroid impact 1 in 20,000 Airplane Crash 1 in 20,000 Flood 1 in 30,000 Tornado 1 in 60,000 Venomous Bite or S7ng 1 in 100,000

28 Jupiter and the Jovian Planets Jupiter, Saturn, Uranus and Neptune

29 Jovian Planets vs. Terrestrial Planets Jovian Planets (Jupiter, Saturn, Uranus & Neptune) Far from Sun Large Low density Many moons Circled by rings Rota7ng rapidly No solid surface Strong storms Terrestrial Planets (Mercury, Venus, Earth & Mars) Close to the Sun Small High density Few Moons No Rings Rota7ng Slowly Solid Surface Weaker winds & storms

30 Jovian Planet Composi7on Jupiter and Saturn Mostly H and He gas Uranus and Neptune Mostly hydrogen compounds: water (H 2 O), methane (CH 4 ), ammonia (NH 3 ) Some H, He, and rock

31 Key Concepts: Jupiter Jupiter is the most massive planet in the solar system Mass of Jupiter = 318 Earth masses Radius of orbit around the Sun = 5 AU orbital period = 12 years rota7onal period = 10 hours 95% of Jupiter is hydrogen and helium Because it is so massive, Jupiter has been able to retain its hydrogen and helium, unlike the Earth Jupiter radiates about twice as much energy as it gets from the Sun It s s7ll cooling off from its forma7on

32 Sizes of Jovian Planets Adding mass to a jovian planet compresses the underlying gas layers.

33 Sizes of Jovian Planets Greater compression is why Jupiter is not much larger than Saturn even though it is three 7mes more massive. Jovian planets with even more mass can be smaller than Jupiter.

34 Rota7on and Shape Jovian planets are not quite spherical because of their rapid rota7on.

35 Jupiter s fast rota7on squished The speed of rota7on at Jupiter s equator is 27 7mes the speed of rota7on at Earth s equator Consequently, Jupiter is squished the equatorial diameter of Jupiter is 6.5% bigger than its polar diameter c.f. for the Earth, the equatorial diameter is 0.3% bigger than the polar diameter

This asteroid was visited by the NEAR Shoemaker probe, which orbited it, taking extensive photographs of its

Chapter 9 Part 1 Asteroids and Comets Why is there an asteroid belt? This asteroid was visited by the NEAR Shoemaker probe, which orbited it, taking extensive photographs of its surface, and, on February