Phobos, The Doomed Moon of Mars

Phobos via HiRISE

Last month the took some incredibly detailed images of the Martian moon , as pictured above. It is incredible to me to see something so far away in such crisp detail. The simple reality that there is so much to learn and see is probably the biggest reason I continue to be fascinated by our solar system and by cosmology.

Mars has two small moons, the other being . Phobos is the bigger of the two, and is about 13 miles across. HiRISE captured a lot of amazing images of this tiny moon, but perhaps the most interesting was a focused shot on the large crater feature named Stickney and shown in the image above. It is the enormous dent on the right side of the moon. If the object that had struck Phobos had been fractionally larger it would very well have blown the moon apart and we would now only know Phobos as a dispersed ring of dust and rock orbiting Mars. Here is an image of the crater in detail:

Phobos crater Stickney via HiRISE

Those lines emanating from the crater are enormous stress fractures caused by the impact and that run outward across the surface. Surviving this impact was an enormous event, but that pales when compared to the realty that the orbit of Phobos is in slow decay (at 1.8 meters per century) and will eventually bring the moon to crash into the Martian surface. Eventually being about 50 million years from now.

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