In 20 to 40 million years, Phobos – the larger of the two Martian moons – will break apart and form a ring system around Mars, according to University of California planetary researchers Tushar Mittal and Dr Benjamin Black.
The Red Planet could gain a ring system in 20 – 40 million years when Phobos is torn to shreds by gravity. Phobos was discovered in August 1877. It orbits 3,721 miles (5,989 km) from the Martian surface and completes an orbit in just 7 hours and 39 minutes. Image credit: Tushar Mittal.
The orbit of the Martian moon Phobos is gradually spiralling inwards towards its parent planet and the small moon is experiencing increasing tidal stresses.
According to Mittal and Dr Black, Phobos is likely to break apart before it hits the Martian atmosphere, leaving a ring system that will persist for up to 100 million years.
In a study published this week in the journal Nature Geoscience, they estimate the cohesiveness of the tiny moon and conclude that it is insufficient to resist the tidal forces.
“Our analysis suggests that much of Phobos is composed of weak, heavily damaged materials,” the scientists said.
“We suggest that – with continued inward migration of the moon – the weakest material will disperse tidally in 20 to 40 million years to form a Martian ring. Any large fragment of Phobos that is strong enough to escape tidal breakup will eventually collide with Mars in an oblique, low-velocity impact.”
“We predict that this ring will persist for 1 million to 100 million years and will initially have a comparable mass density to that of Saturn’s rings.”
To estimate the strength of Phobos, Dr Black and Mittal looked data from similarly fractured rocks on Earth and from meteorites that struck our planet and have a density and composition similar to the Martian moon.
The scientists also constrained the strength of Phobos based on results from simulations of the massive Stickney crater, which formed in the past when a rock rammed into Phobos without quite smashing the moon apart.
“It’s not clear whether the Martian dust and debris ring would be visible from Earth, since dust does not reflect much sunlight, whereas ice in the rings of the outer planets makes them easily visible,” Mittal said.
“But the ring may reflect enough light to make Mars slightly brighter as seen from Earth, and through a telescope the shadows of the rings might also be visible on the surface.”
“Standing on the surface of Mars a few tens of millions of years from now, it would be pretty spectacular to watch,” Dr Black added.
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Benjamin A. Black & Tushar Mittal. The demise of Phobos and development of a Martian ring system. Nature Geoscience, published online November 23, 2015; doi: 10.1038/ngeo2583
