31. Why are there craters? How do they form? (A K2S Question)

From The Space Library

A crater is a natural result of an asteroid hitting the Moon at high velocity. When the object strikes the Moon it comes to a very sudden stop, releasing a large amount of kinetic energy. This effectively vaporizes and explodes the object. It is considered a point-source as far as the explosion is concerned, and so the force radiates outward spherically. This means that a crater will be circular even if the impactor doesn't come straight down to the Moon's surface. Only at a really shallow angle will an oblong crater be formed. The force emitted downwards will compress and shock the underlying material, but there's really nowhere for it to go, with a whole planet blocking the way. The force emitted upwards will blow the surface material upwards and outwards. Most of the big stuff will stay right near the crater rim, medium sized pieces may make secondary craters farther out, and lighter material may form lighter-colored rays radiating outwards from the newly formed crater.

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Answer provided by Thomas Matula, Ph.D. & Kenneth J. Murphy

Question and Answer extracted from the book Kids to Space - by Lonnie Schorer

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