NASA scientists have released new modelling that suggests the long, shallow grooves lining the surface of Martian moon Phobos are the early signs of the structural failure that will ultimately destroy it.
Phobos and Mars are closer than any other planet and moon in the solar system – just 6,000 kilometres apart. And gravity draws Phobos nearer by two metres every 100 years.
So while the end is more or less certain, it won’t happen soon. Scientists expect the moon to be pulled apart in 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 Greenbelt, Maryland.
The findings by Hurford and his colleagues were presented at the annual Meeting of the Division of Planetary Sciences of the American Astronomical Society at National Harbor, Maryland.
Phobos’ grooves were long thought to be fractures caused by the impact that formed Stickney crater. That collision was so powerful, it came close to shattering Phobos. However, scientists eventually determined that the grooves don’t radiate outward from the crater itself but from a focal point nearby.
More recently, researchers have proposed that the grooves may instead be produced by many smaller impacts of material ejected from Mars. But new modeling by Hurford and colleagues supports the view that the grooves are more like “stretch marks” that occur when Phobos gets deformed by tidal forces.
Bill Condie is a science journalist based in Adelaide, Australia.
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