New scientific modeling indicates that the grooves on Mars’ moon Phobos could be produced by tidal forces – the mutual gravitational pull of the planet and the moon. Initially, scientists had thought the grooves were created by the massive impact that made Stickney crater (lower right). Credits: NASA/JPL-Caltech/University of Arizona
NASA scientist have discovered that Mars’ moon, Phobos, is slowly breaking apart due to the Red Planet’s gravitational pull.
Orbiting a mere 3,700 miles (6,000 kilometers) above the surface of Mars, Phobos is closer to its planet than any other moon in the solar system. Mars’ gravity is drawing in Phobos, the larger of its two moons, by about 6.6 feet (2 meters) every hundred years. 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 grooves on Phobos 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.
The gravitational pull between Mars and Phobos produces these tidal forces. Earth and our moon pull on each other in the same way, producing tides in the oceans and making both planet and moon slightly egg-shaped rather than perfectly round.
The same fate may await Neptune’s moon Triton, which is also slowly falling inward and has a similarly fractured surface. The work also has implications for extrasolar planets, according to researchers.
“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 Hurford.
Image credit and article source: NASA