One of Mars’ moons is falling apart, and it won’t be the only one

11 Nov 2015

Image of Phobos via ESA

The fate of Mars’ moon Phobos appears to be one of inevitable collapse, NASA says, with implications that other moons in the solar system will see the same demise.

Phobos is one of the clingiest moons in the solar system to its parent planet, orbiting just 6,000km above Mars’ surface and, because of this, it’s likely that this will lead to its inevitable collapse.

According to NASA, the gravitational pull Phobos is experiencing from Mars pulls it ever closer at a rate of two metres every 100 years.

At this rate, the agency said, it will reach its breaking point and pull apart within 30m and 50m years.

The telltale signs, according to NASA, are the long, shallow grooves along the moon’s surface, which are indications of its structural failure, originally thought to have been the result of a major impact at its Stickney crater.

Recent hypothesis of the moon’s interior would also pay credence to Phobos not having much hope for a long-term future due to its interior, which is now believed to be mostly loosely-connected space debris kept together by a layer of powdery regolith about 100 metres thick.

“The funny thing about the result is that it shows Phobos has a kind of mildly cohesive outer fabric,” said co-investigator on the study, Erik Asphaug. “This makes sense when you think about powdery materials in microgravity, but it’s quite non-intuitive.”

The researchers of the study also warned that Phobos is not the only moon in the solar system expected to undergo the same gravitational stresses, with the same demise expected of Neptune’s moon Triton as well as some other extrasolar planets.

“We can’t image those distant planets to see what’s going on, but this work can help us understand those systems, because any kind of planet falling into its host star could get torn apart in the same way,” said another investigator on the study, Terry Hurford.

But before it dies, long after we are all cosmic dust, the Japanese space agency JAXA plans to land a spacecraft on the moon’s surface by 2022 to further study its surface.

Colm Gorey was a senior journalist with Silicon Republic