Impact crater Lab

Some notes about cratering

1

Meteors

Updated july 19, 2009

Meteorites are …

Most come fromthe asteroids, butsome are chips fromthe Moon and someare from Mars.

3

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. Nowin the Hayden Planetarium,New York City.

1906 photo

4

Many meteorites have been recovered in Antarctica

Meteorites are preservedin the Antarctic ice cap.

The are concentrated incertain areas by themotion of the ice.

Meteorites are easier to find in the icebecause there are veryfew “native” rocks.

A few thousand havebeen found so far.

5

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

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.

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Formation of an impact crater

Impacts occurat velocitiessome 10-20times the speedof a rifle bullet.

This produces apowerfulexplosion.

8

The 1 mile diameter Barringer Crater (Arizona) was probably created by a 45

meter object, 50,000 years ago.

9

Sahara Impact: 148 feet diameter10

• 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

The Moon’sother side

There arevery fewmaria onthe Moon’sfar side.

We’re notsure why.

12

The great Eastern Basin, Mare Orientale

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• Virtually all lunar craters were caused by space debris striking the surface

• There is no evidence of plate tectonic activity on the Moon

14

Asteroid 2011 MD flew past Earth on Monday, June 27th (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.

15

http://neo.jpl.nasa.gov/news/news172.html

October 17, 2012, a car-sized meteor passed northward over the Hayward hills.

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http://www.youtube.com/watch?v=pFjC04A8_WUhttp://earthsky.org/space/many-in-bay-area-heard-and-saw-bright-meteor-on-october-17

Feb 15, 2013, Russian Meteor Event

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http://en.wikipedia.org/wiki/2013_Russian_meteor_eventVideos: http://rt.com/news/meteorite-crash-urals-chelyabinsk-283/http://www.youtube.com/watch?v=L-VlIWSDbn4

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

Impact Crater: Power Model

y = 0.1042x0.2398

R2 = 0.95340.060

0.080

0.100

0.120

0.140

0.160

0.000 1.000 2.000 3.000 4.000 5.000

Energy (Joules)

Dia

met

er (m

eter

s)

Sample Student Data (not very good) Mass (kg) height (m) v (m/s) D1 D2 D3 Avg D E (J) Log E

0.22758 1.64 5.67 0.15 0.145 0.15 0.148 3.658 0.563 0.22758 1.47 5.37 0.135 0.14 0.14 0.138 3.279 0.516 0.22758 1.735 5.83 0.145 0.15 0.155 0.150 3.870 0.588 0.22758 1.25 4.95 0.13 0.1325 0.115 0.126 2.788 0.445 0.22758 0.93 4.27 0.12 0.125 0.125 0.123 2.074 0.317 0.04993 0.93 4.27 0.094 0.085 0.09 0.090 0.455 -0.342 0.04993 1.22 4.89 0.099 0.09 0.094 0.094 0.597 -0.224 0.04993 1.47 5.37 0.095 0.095 0.094 0.095 0.719 -0.143 0.04993 1.62 5.63 0.093 0.094 0.093 0.093 0.793 -0.101 0.04993 1.76 5.87 0.101 0.105 0.1 0.102 0.861 -0.065 0.02809 0.93 4.27 0.075 0.08 0.085 0.080 0.256 -0.592 0.02809 1.22 4.89 0.091 0.081 0.08 0.084 0.336 -0.474 0.02809 1.47 5.37 0.075 0.075 0.079 0.076 0.405 -0.393 0.02809 1.62 5.63 0.081 0.08 0.077 0.079 0.446 -0.351

0.02809 1.76 5.87 0.09 0.085 0.099 0.091 0.484 -0.315

19Note: 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).

References20

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