Mars and its moon Phobos are super close — physically, at least. Phobos is just 3,700 miles from the surface of Mars, over 60 times closer than we are to our own moon. But the emotional bond between Mars and Phobos is probably a little rocky, according to some new findings.
The gravitational pull between Mars and Phobos has already left the moon with scars, according to Hurford and his colleagues, and in 30 to 50 million years this planetary tug of war could end with Phobos crumbling up and colliding with its host planet.
Hurford and his colleagues were looking for an explanation for Phobos’s deep, mysterious grooves. Several historical impacts have been floated as probable causes for the fissures, but some scientists argue that the extent and regularity of the cracks just can’t be explained by a collision with space debris. The new model suggests that the cracks are actually stretch marks of a sort, caused by the way the moon squishes and squashes under intense tidal forces.
For this process to work, Phobos would have to have a pretty weird interior: The model paints a picture of Phobos as a pile of rubble surrounded by a powdery shell about 330 feet thick. The interior would warp and wobble in response to gravitational tugs, while the exterior layer would have enough elasticity not to keep itself together — but not enough to prevent occasional cracks.
Scientists are eager to learn more about whatever is causing Phobos’s groovy surface. The martian moon is close enough that we could send a probe to take a closer look at it one day. If Mars is truly tearing its moon apart, then the process could teach us what to expect from other disastrous couplings far off in the galaxy.
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