Today's Image of Mars shows a remarkable doublet crater! A doublet crater is formed when two objects impact the surface at the same time. But how does this happen?
Because the likelihood of two separate meteorites hitting the same place at the same time is so small, we assume that one loosely connected asteroid or comet split apart just before it hit the surface. The asteroid/comet would have split apart, but because of inertia, both pieces would have continued in essentially the same direction at the same velocity, separating only slightly. Thus they would impact locations nearby one another at almost the same time, thus forming the doublet imaged by HiRISE that we see below.
Clicking on this image will take you to the original high resolution image from HiRISE.