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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