Keep an eye on Mars – one day it will have rings!

Yes – its been speculated about, and now scientists have concluded that Mars will one day have a set of planetary rings that will rival those of the mighty Saturn.  Good news and Bad news though.  The good news is that the spectacular event will be much closer to all the enthusiastic astronomers here on Earth, but the bad news is, it may not happen for another 30 million years.

This planetary news headline came about after extensive modelling and study of Mars’ closest moon, called Phobos.  In case you hadn’t heard of Phobos before, it is a diminutive satellite which orbits very close to the surface of Mars.  At only 28 km wide, Phobos is little more than a space rock, but the interesting part is that it orbits only 6000 km from the Martian surface, and it orbits very rapidly.  In fact, Phobos completes an orbit every 7 hours and 39 minutes, which means it completes more than two rotations every Martian day.

Whilst this may seem incredible by the standards of our Moon, and our daily rhythm, this rapid orbital speed is not surprise to scientists.  Due to the separation distance from Mars, and due to the gravity differential between Mars and the smaller satellite, the moon is required to rotate at such speeds to stay in orbit.

But not quite!

In fact, Phobos is actually falling, very gradually, by around 2 cm per year, towards the surface of Mars, while still maintaining its incredible orbital speed.  Now here is the interesting part.  Falling is not going to be the downfall of Phobos.

The internal structure of Phobos has been extensively studied (well as much as remotely possible) and structural models have been recreated here on Earth, from what we know of the structural materials of the distant moon. Scientists have concluded that Phobos is stretched by the enormous stress of the gravitational pull of Mars, and the centripetal force of the orbital rotation, such that the structure of the moon will succumb to these forces before the moon will actually crash into Mars.  Not good news if you are a moon.  Instead of crashing, Phobos is expected to be pulled apart by the extreme tidal forces exerted by Mars and subsequently break up into millions of rocks, dust and space debris.  Although this sounds very apocalyptic, there is precedence!  Scientists are confident that the same explanation is plausible for the creation of the spectacular rings around Saturn, and to a lesser extent, some of the other planetary rings in the solar system.


Scientists have also been able to make conclusions about the future of Phobos by studying the existing formations on the little satellite.  For many years, the existence of stretch marks was observed, but not readily explained.

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The surface features of the 28km moon highlight elongated linear channels, which have in the past been interpreted as fallout from significant impact collisions.  Now scientists believe that the grooves may actually be stretch marks which are indications of the gravitational tug of war.  The competing forces of the rapid orbit and Martian gravity are stretching the tiny satellite, resulting in a slow deformation of the surface of the moon, and once the deformation becomes more than the structure can maintain, will eventually tear Phobos to pieces.

Scientists were able to conclude that the amount of force required to break up Phobos would be sufficient somewhere an orbit of 8000 and 4000 km.  Hang On!  As Phobos is now orbiting around 6000 km from Mars, the break up could be imminent.  If the interpretation of the stretch marks is correct, Phobos is already under enormous stress, and maybe the break up process could happen at any time.

And it will happen quickly

Okay, so we don’t know exactly when it might happen, but be warned, when it does happen, it may happen within a matter of hours, to break up and disperse a ring of material completely around Mars, and for a debris ring to encircle the planet.  The resulting debris made up of rocks, dust and other particles will disperse away from the surface into the characteristic patterns that we see around Saturn, and form distinctive rings, gaps, and colorful arrangements depending on the size and speed of the particles.

Wouldn’t that be exciting to see the formation of a whole new planetary spectacle, and much nearer to Earth!  Just don’t hold your breath in anticipation; it might take another 10 or 30 million years to happen!

Get your brand new telescope ready just in case!


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