Early Stages Of Crater Birth

The resulting craters form in 100 milliseconds or less. By using high-speed video cameras that can capture up to 15,000 frames per second, the team could track individual sand particles as they were ejected from the impact.

Most of the material thrown up by the impact took to the air during the impact's "main stage", landing within a few crater radii of where the projectile hit. But the high-speed video also revealed particles kicked up in a relatively unstudied early stage.

During this phase of crater formation material is flung fastest and farthest, for example creating the long rays of the moon's Tycho crater and, potentially, launching a number of meteoroids into space from the surface of the moon and Mars.

The new experiments show the material released during this early stage is ejected faster and at a lower angle than the main stage.

Crater makers

Learning more about how such debris is ejected could help researchers to piece together the trajectory, speed and other properties of the bodies – such as comets, meteoroids and asteroids – that have made craters on the moon and other bodies, Hermalyn says.

This is the first time particle tracking has been used to measure the speeds and angles of particles thrown out in the early stage of impact, says Jay Melosh of Purdue University in West Lafayette, Indiana.

The speeds of impacts in the experiment are much lower than the average for bodies like the moon and so can't reproduce effects such as melting and vaporisation that more energetic impacts cause, says Melosh. But he says the experiment could be an important check for computer models of impacts.