Martian moon Phobos shows signs of impending destruction

It seems that our red neighbor just can't catch a cosmic break. After losing most of its atmosphere and almost all of its water thanks to bombardment from the sun, Mars is now likely to lose one of its moons in a few million years. Phobos, the moon that orbits closest to Mars, is showing external signs that it might be on its way out and could fall apart in 30 to 50 million years. This time, however, it might be Mars itself that will be partly to blame.

Phobos, named after the Greek god of fear and son of war god Ares, orbits only 3,700 miles or 6,000 kilometers from its planet. In our solar system, that's the closest proximity of any moon. We are already familiar with how our own planet and moon's tug of gravitational war causes tidal waves. That is the same game of physics between Mars and Phobos but on a greater scale because of their distance. Scientists have posited that Phobos gets closer to Mars by 6.6 feet or 2 meters every hundred or so years.

But collision with Mars isn't exactly the end game for Phobos. Structural failure and breaking apart is actually the more inevitable scenario. That is because of what scientists now believe to be the composition of Phobos' innards. The most recent models lead them to believe that Phobos' insides are nothing more than a pile of rubble being held together, barely, by a powdery regolith region about 330 feet or 100 meters in thickness. In short, it's like a "mildly cohesive outer fabric" that is barely keeping Phobos's interior rocks together.

The stress that Mars' pull is putting on Phobos is manifested in shallow grooves across the surface of its moon, appropriately being called as stretch marks. Previously, these marks were thought to have been fractures caused by a forceful impact that also produced the Stickney crater, the large dimple you can see on the right side of the photo above. But scientists have discovered that some of those grooves are younger than the others, hinting that their cause is an ongoing phenomenon rather than something in the very distant past.

Phobos, fortunately or unfortunately, isn't going to be alone in this fate. Triton, Neptune's moon, coincidentally also named after a son of the sea god, might also end up the same way, as scientists theorize that it is also falling inward due to signs of the same stretch marks. These phenomena are being used as models of what may happen to a planet, any planet, perhaps even our own, that will have the luck to start falling into its host star.