Mars will get ring like Saturn, scientists predict

The Red Planet could find itself wearing a stylish new accessory in tens of millions of years.

Moon Phobos is making a death spiral that will result in it getting torn to pieces, study suggests

Mars's moon Phobos is spiralling toward the Red Planet, and within 40 million years, it's expected to break apart to form a ring, or crash into Mars. ( NASA/JPL/University of Arizona)

The Red Planet could find itself wearing a stylish new accessory in tens of millions of years.

A ring like Saturn's will likely form from the shattered remains of Mars's moon Phobos when that moon breaks apart in about 20 to 40 million years, predict planetary scientists in a new paper published Monday.

The ring is expected to last for up to 100 million years.

Phobos, the larger of Mars's two moons, is gradually spiralling towards Mars. As it gets closer, Mars's gravity is pulling harder on the side closest to the planet, producing forces known as "tidal stresses."

"Eventually, Phobos will either break apart to form a ring or it will crash into Mars," postdoctoral researcher Benjamin Black, of University of California, Berkeley, and graduate student Tushar Mittal wrote in the journal Nature Geoscience.

The pair evaluated which possibility was more likely, and concluded that ring formation would win out.

The researchers noted that Phobos has a low density, suggesting it's very porous. It has a similar chemical fingerprint to meteorites called carbonaceous chondrites, which are not strong because of chemical reactions with water that weaken them.

The oval-shaped moon, which is 27 kilometres long and 18 kilometres wide along its longest and narrowest dimensions, also has a crater on it that is 10 kilometres in diameter, suggesting it was heavily damaged when it was hit by the object that produced the crater.

That means Phobos is unlikely to stay together long enough to smash into Mars.

Instead, Mars's pull on the moon's near side will break it into pieces that will reform into a ring with "comparable mass density to that of Saturn's rings."

The researchers added that a number of missions to Phobos have been proposed, and those spacecraft might be able to make measurements that will help test their prediction.

All four of the outer planets in our solar system – Jupiter, Saturn, Uranus and Neptune – are encircled by rings.

None of the inner planets has a ring.

However, computer simulations suggest that Earth-like planets could gain rings from events including collisions with other objects, such as moons that migrate toward the planet they orbit.


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