[X] My Assistant

[ramjet146]

I'm an electonic technician, and my hobby is 3d graphics. Could someone explain to me why nearly all craters on mars and the moon have impacts that appear to be at right angles to the surface. This should be to my way of thinking an impossibility since everything in our System is rotating and moving. surelly there has to be a majority of tangentially made craters. Victoria is straight in, or is it a collapse.

[Phil Stooke]

Is it the circularity of the craters that makes you think they were created by vertical impacts?

This is a misconception which was resolved by Gene Shoemaker in his studies of Meteor Crater and artificial expolosion craters in about 1960. Impact craters are not mechanically excavated by the impactor - so it's not like throwing a stone into a pile of sand. They are made by a shock expanding out from the impact point as a circular 'wave', like ripples in a pond. Only an extremely low angle oblique impact makes an elliptical crater.

Phil

[ramjet146]

Thanks for the info Phil,
I should have thought of the shockwave. sometimes things don't gel straight away.
I wish I was smart enough to get Isis up on a linux system and use their Photoclinometry tools. My brother and I use the sandbox editor out of a game called FarCry to read in Raw heightfield files for terrain. Then walk around on any scene. Hope a DEM of Victoria appears somewhere.

[dvandorn]

I will add to this discussion, that while only very low-angle impacts create elliptical craters, depressed-angle impacts do produce (to a greater or lesser degree) asymmetrical ejecta blankets. While the shock of the impact creates a spherical blast wave (which manifests as a roughly circular crater), the angle of the impactor and the direction in which it was traveling when it impacted (among other things) determines how the ejecta is sprayed.

There are many circular craters on the Moon with very non-circular ejecta blankets, mostly due to angle of impact...

-the other Doug