1. Impact crater Lab Some notes about cratering 1

2. Meteors Updated july 19, 2009

3. Meteorites are … Most come from the asteroids, but some are chips from the Moon and some are from Mars. 3

4. Some meteorites are big This is an iron meteorite 15-ton meteorite found in the Willamette Valley, Oregon Known to native Americans, but “discovered” in 1902. Now in the Hayden Planetarium, New York City. 1906 photo 4

5. Many meteorites have been recovered in Antarctica Meteorites are preserved in the Antarctic ice cap. The are concentrated in certain areas by the motion of the ice. Meteorites are easier to find in the ice because there are very few “native” rocks. A few thousand have been found so far. 5

6. The Importance of Meteorites They are the oldest material that we have. Their ages are consistently 4.45 to 4.57 billion years. Meteorite ages are determined from the radioactive atoms in them. You have seen these two figures before … 6

7. A final critical point … The age of the formation of the Solar System (that is, the condensation of solid material from gas and dust) is based on the ages of the meteorites. This is where we get the figure 4.6 billion years for the age of the Earth, the other planets, and the Sun It is based on hundreds of independent age measurements on hundreds of different meteorites. 7

8. Formation of an impact crater Impacts occur at velocities some 10-20 times the speed of a rifle bullet. This produces a powerful explosion. 8

9. The 1 mile diameter Barringer Crater (Arizona) was probably created by a 45 meter object, 50,000 years ago. 9

10. Sahara Impact: 148 feet diameter 10

11. The Moon is one- fourth the size of the Earth The light gray areas are called highlands – they are heavily cratered and mountainous The dark black/gray areas are called maria – they are lightly cratered and relatively smooth Crustal Dichotomy 11

12. The Moon’s other side There are very few maria on the Moon’s far side. We’re not sure why. 12

13. The great Eastern Basin, Mare Orientale 13

14. Virtually all lunar craters were caused by space debris striking the surface There is no evidence of plate tectonic activity on the Moon 14

15. Asteroid 2011 MD flew past Earth on Monday, June 27 th (2011). At closest approach the ~10-meter space rock was only 12,000 kilometers (7,500 miles) above the planet's surface. NASA analysts said there was no chance it would strike Earth, and indeed it didn't.no chance 15 http://neo.jpl.nasa.gov/news/news172.html

16. October 17, 2012, a car-sized meteor passed northward over the Hayward hills. 16 http://www.youtube.com/watch?v=pFjC04A8_WU http://earthsky.org/space/many-in-bay-area-heard-and-saw-bright-meteor-on- october-17

17. Feb 15, 2013, Russian Meteor Event 17 http://en.wikipedia.org/wiki/2013_Russian_meteor_event Videos: http://rt.com/news/meteorite-crash-urals-chelyabinsk-283/http://rt.com/news/meteorite-crash-urals-chelyabinsk-283/ http://www.youtube.com/watch?v=L-VlIWSDbn4

18. Sample Data: By dropping different sized balls from varied heights we get a range of energies. A plot of crater diameter vs energy shows a clear power relationship 18

19. 19 Note: each “drop” was repeated 3 times, diameters (D1, D2, D3) were then averaged to decrease error. Energy is calculated: E=mgh A bigger range in energy would be better (big masses from 2 meters, smaller masses from low heights).

20. References 20 List of impact craters on the earth http://en.wikipedia.org/wiki/List_of_impact_craters_on_Earth