What if Earth and the Moon Were Hit by Twin Asteroids?
 ES2506 Collision Physics
At the moment of impact, an asteroid essentially explodes, excavating a crater. The size and structure of the crater depend mostly on the kinetic energy of the object that created it, and to some extent on the angle of impact and the gravity and composition of the target body.

An object's kinetic energy depends on its mass and speed. A typical speed for asteroids approaching Earth and the moon is around 17 km/s. Mass is calculated from the asteroid's diameter and density. Typical diameters are up to a few hundred kilometers, and densities range from 3 g/cm3 (rock) to 8 g/cm3 (iron). The angle of impact ranges from 90 degrees (a direct hit) to 0 degrees (a glancing blow).

!   Examine the images and information, and answer question 6 below.

Moon Craters

Earth Craters

 NASA Simple Crater Moltke Crater Diameter 7 km
 D. Roddy, USGS Simple Crater Barringer Crater, Arizona Diameter 1.3 km
 NASA Complex - Central Peak Euler Crater Diameter 28 km
 NASA Complex - Central Peak Mistastin Crater, Canada Diameter 28 km
 NASA Complex - Central Ring Schrodinger Crater Diameter 320 km
 NASA Complex - Central Ring Clearwater Lakes, Canada Diameter 32km
 NASA Multi-Ring Basin Mare Orientale Diameter 970 km
 VL Sharpton, LPI Multi-Ring Basin Chicxulub Impact Basin, Mexico Diameter >170 km
 These examples show a range of size and form for impact craters. Simple craters have raised rims and simple bowl shapes. As the crater size increases, loose debris in the crater walls slumps inward to partially fill the crater floor.     Complex craters have a central peak or ring, depending on their size. These features are caused by the elastic rebound of the surface material following the impact. Slumping fills the floor with debris, making complex craters relatively shallow.       Larger complex craters have multiple rings, and the largest, called impact basins, are hundreds of kilometers in diameter.
6. The acceleration of gravity (g) on Earth is 9.8 meters/sec2, but on the moon, it is only 1.6 meters/sec2. How might this relate to the sizes of craters produced by impacts with identical amounts of kinetic energy on the two bodies?
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