Mars Hit By Cosmic Buckshot, Again

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The Martian atmosphere is the Red Planet's blessing and curse.

The blessing is that the Martian atmosphere is so tenuous it allows relatively small lumps of space rock to turn into meteorites, peppering its surface with fascinating impact craters for our satellites to study from orbit.

As fun as this may be for us remote observers, should Mars colonization be in our future, we'll be cursing this fact should our habitats get punctured -- or destroyed -- by cosmic buckshot.
Fortunately for us, Earth has a hefty atmosphere, some 100 times thicker than Mars, ensuring any renegade space rocks are tortured by the extreme heating of atmospheric entry -- only the largest, toughest rocks survive the burn.

But on Mars, as this detailed photograph from the High-Resolution Imaging Science Experiment (HiRISE) camera on board NASA's Mars Reconnaissance Orbiter (MRO) shows, it receives a fairly regular peppering from space.

Occurring some time between Dec. 2002 and March 2008, this series of impact craters sprayed pockmarks over a distance of approximately 120 meters (~400 feet) in the Terra Sabaea region. It's most likely that all the individual impact craters originated from a larger meteoroid that broke up in the atmosphere.

Interestingly, judging by the impact ejecta, the meteorites may have hit the surface at an oblique angle (rather than impacting vertically), raining down from a northwesterly direction (from top left to bottom right).

Also, the two largest impact craters in the center of the series are separated by a definite line of impact debris. This was most likely caused by the darker material being kicked up simultaneously by both impacts, colliding and settling atop the lighter regolith on the surface.

Although we can only infer how this series of impact craters were formed from a photograph 290 kilometers (180 miles) above the Martian surface, the HiRISE camera continues to give us some of the most detailed and beautiful views of this alien landscape.

http://news.discovery.com/space/mars-hi ... 10613.html