Mars Had Once a Ring, Here is Why


Mars – the dusty and glorious Red Planet – might once have been even more brilliant. 

A recent study offers more proof that a rubbly ring once surrounded Mars. Deimos, the smaller of the two Martian moons, is where the new clue lies. Here are the latest details.

New Proof That Mars Had a Ring

The ring systems aren’t that common. When we think about them, we immediately imagine Saturn. But half of the planets in the Solar System possess rings, Uranus, Jupiter, Neptune, and Saturn, of course. The centaurs Chariklo and Chiron, and the dwarf planet Haumea also have rings. So, what are the chances that Mars once had a ring?

Back in 2017, a team of researchers believed that Mars, too, once possess a ring. They realized a series of simulations of the bigger of the two Martian moons, Phobos. The researchers discovered that the Martian moon could have developed after an asteroid hit Mars, discharging debris into space, creating a ring that then bumped together into an earlier Phobos – much larger than it is today. The recent study has added Deimos into the mix. Now the findings are in full agreement with the initial model. 

Deimos’ orbital angle isn’t massive – only 1.8 degrees off the Red Planet’s equator. Aside from that, its orbit seems reasonable – it twirls around Mars every 30 hours, with low eccentricity. But, as normal as it might be, there is something odd going on with Phobos. 

Within 100 million years, researchers expect Phobos to reach the Roche limit, the length from Mars at which the planet’s tidal forces shred the moon apart. A lot of debris could create a ring that rains down on the Red planet; but some of it could turn into a newer, smaller Phobos that gets shoved outwards as the ring is drawn in. 

Such a phenomenon, according to the 2017 study, could have occurred several times before. And this is where Deimos proves its efficacy. 

Utilizing numerical simulations, the team tried to model this time around how such an outward-passing proto-Phobos would have influenced Deimos’ orbital tilt. The results are incredible. Researchers succeeded in arriving at a proto-Phobos 20 times the moon’s actual mass, which would have reached a 1:3 orbital resonance with Deimos at a length of 3.3 Mars radii that forced the latter’s orbit into a small inclination. 

“Once it (the ring) was too close to Mars, tidal forces would pull it apart into a new ring, and the cycle would repeat, probably twice, to get to Phobos we see,” explained astronomer Matija Cuk of the SETI Institute. 

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