Mars' Moon Phobos is Being Torn Apart by the Red Planet

It turns out that Mars' moon, Phobos, is slowly falling apart. Scientists have taken a closer look at this moon and have found that it's showing early signs of structural failure that will ultimately destroy it.

Phobos orbits just 3,700 miles above the surface of Mars, which means that it's closer to its planet than any other moon in the solar system. Over time, Mars' gravity is drawing in Phobos by about 6.6 feet every hundred years. This means that the moon also has to deal with gravity to an extent that it's at risk of being pulled apart. In fact, researchers estimate that it will crumble in just 30 to 50 million years.

"We think that Phobos has already started to fail, and the first sign of this failure is the production of these grooves," said Terry Hurford of NASA's Goddard Space Flight Center, in a news release.

Phobos' grooves were long thought to be fractures caused by the impact that formed Stickney crater. That collision was so powerful that it came close to shattering Phobos. However, scientists eventually found that the grooves didn't radiate outward from the crater itself, but instead from a focal point underneath.

In fact, new modeling reveals that these grooves are actually "stretch marks" that occur when Phobos gets deformed by tidal forces. These forces are created by the gravitational pull between Mars and Phobos.

The new results suggest that the interior of Phobos could be a rubble pile rather than solid all the way through. This pile, which is barely holding together, is surrounded by a layer of powdery regolith about 330 feet thick.

"The funny thing about the result is that it shows Phobos has a kind of mildly cohesive outer fabric," said Erik Asphaug, one of the researchers. "This makes sense when you think about powdery materials in microgravity, but it's quite non-intuitive."

The findings reveal a bit more about Phobos, and may help researchers understand other systems, as well.

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