Moon could put a ring on Mars

An illustration of Mars and Phobos before the two become one (iStock)
An illustration of Mars and Phobos before the two become one (iStock)

One of Mars' moons likes it so much it could eventually put a ring on it, scientists believe.

But it could be a long engagement, with researchers from the University of California Berkeley predicting Mars' bigger moon Phobos could break apart in 20-40 million years.

That'd give the red planet its own ring just like Saturn, Jupiter, Uranus and Neptune, and it could be there for up to 100 million years.

The study was published in Nature Geoscience today and says the ring could eventually have the same density as Saturn's.

Authors Benjamin Black and Tushar Mittal say Phobos is gradually spiralling toward Mars, unlike Earth's moon which is spiralling away.

They believe Phobos will eventually either break apart because of increasing tidal stresses induced by the planet's gravitational pull or crash into the planet – the expected outcomes for such situations.

Using observational data and a geotechnical model to calculate the strength of the moon, they found it was made of weak materials, though any large piece of it which stays intact when it breaks up will give the planet a new crater.

The authors don't address what may happen to Mars' smaller moon Deimos.

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