Phobos is Falling Apart

Sorry Mars, but I wouldn’t get so used to having Phobos around for much longer. It has been discovered that Phobos, the smaller of Mars’ two moons, has long, thin “stretch marks” on it’s surface that indicate that it is falling apart. Phobos is actually closer to Mars than any other moon is in relation to its respective planet. As a result of this, every 100 years or so Phobos gets closer and closer to Mars by 6.6 feet (2 meters). As the moon gets closer, the effect of Mars’ gravity acting on it increases. Research suggests that in 30 million-50 million years, Mars’ famous moon will be no more. It was originally thought that the “stretch marks” or grooves were created when another celestial body collided with Phobos. But after analyzing the grooves, it was determined that this was not the case, as they were too far away from the crater left behind after the impact. We now know that as Mars’ gravity pulls at Phobos, it causes stress fractures on the smaller body (Phobos). Back when the Viking spacecraft originally took photos of Phobos, scientists thought that it was a solid body, and thus would be less likely to fall apart. However, observations today suggest that Phobos is really more of a loose ball of rubble than a solid body of rock. Mars isn’t the only planet planning on losing a moon soon, evidence suggests that Neptune’s moon, Triton, awaits the same fate as Phobos. Triton is slowly falling inward and shares similar marks on its surface as the ones that are on Phobos.

Phobos color.png
The streaks or “stretch marks” seen above are evidence that Phobos is slowly breaking apart. Photo by NASA

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