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| The grooves on Mars' moon Phobos could be produced by tidal forces – the mutual gravitational pull of the planet and the moon, says NASA. The theory is the latest explanation for grooves that were once thought to result from the massive impact that caused the Stickney crater (lower right). (Credit: NASA/JPL-Caltech/University of Arizona) |
By www.npr.org
11-11-15
Spinning in orbit just 3,700 miles above the Mars' surface, the planet's largest moon, Phobos, seems to be undergoing a "structural failure," NASA says, providing a new explanation about a moon whose odd features have sparked many theories — including the idea that Phobos is hollow.
"Mars' gravity is drawing in Phobos, the larger of its two moons, by about 6.6 feet (2 meters) every hundred years," NASA says. "Scientists expect the moon to be pulled apart in 30 to 50 million years."
The story of Phobos' doom is written on its surface, where grooves that resemble stretch marks signal stress fractures, according to NASA scientists.
"We think that Phobos has already started to fail, and the first sign of this failure is the production of these grooves," says Terry Hurford of NASA's Goddard Space Flight Center in Maryland. [...]
