Though inevitable, the demise of Phobos is not imminent. It will probably happen in 20 to 40 million years, leaving a ring that will persist for anywhere from one million to 100 million years, according to two young planetary scientists Tushar Mittal and Benjamin Black from the University of California, Berkeley.
In a paper appearing in Nature Geoscience, they have estimated the cohesiveness of Phobos and conclude that it is insufficient to resist the tidal forces that will pull it apart when it gets closer to Mars.
Just as earth’s moon pulls on our planet in different directions, for example raising tides in the oceans, so too Mars tugs differently on different parts of Phobos. As Phobos is highly fractured with lots of holes, when it gets closer to the planet, the tugs are enough to actually pull the moon apart.
|The timescales for orbital evolution.|
“While our moon is moving away from earth at a few centimeters per year, Phobos is moving toward Mars at a few centimeters per year, so it is almost inevitable that it will either crash into Mars or break apart,” Black said.
“One of our motivations for studying Phobos was as a test case to develop ideas of what processes a moon might undergo as it moves inward toward a planet.,” he added. Only one other moon in the solar system, Neptune’s largest moon, Triton, is known to be moving closer to its planet.
Mittal said it’s not clear whether the dust and debris rings 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.
But, one thing we can expect - standing on the surface of Mars a few million years from now, would be pretty spectacular to watch.
article reference:- berkeley.edu