The Moons Of Mars: Deimos & Phobos

rynner2

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re: Mars and Phobos (above):

The Roche limit (pronounced /ʁoʃ/ in IPA, similar to the sound of rosh), sometimes referred to as the Roche radius, is the distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body's tidal forces exceeding the first body's gravitational self-attraction.[1] Inside the Roche limit, orbiting material disperses and forms rings whereas outside the limit material tends to coalesce. The term is named after Édouard Roche, who is the French astronomer who first calculated this theoretical limit in 1848.

etc...

https://en.wikipedia.org/wiki/Roche_limit
 

EnolaGaia

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... Phobos will eventually disintegrate and form a ring around the red planet. ...
Newly published research suggests this wouldn't be the first time there was a ring around Mars. For one thing, both the Phobos and Deimos of today may have coalesced from a prior ring - perhaps more than once.
We Just Got Even More Evidence Mars Once Had a Ring

New research provides even more evidence that a rubbly ring once circled the Red Planet.

The new clue lies in Deimos, the smaller of the two Martian moons. It's orbiting Mars at a slight tilt with respect to the planet's equator - and this could very well be the result of the gravitational shenanigans caused by a planetary ring.

Ring systems aren't actually all that uncommon. When you think about ring systems, your mind immediately leaps to Saturn, no doubt - but half the planets in the Solar System have rings, Saturn, Uranus, Neptune, and Jupiter. Dwarf planet Haumea, and centaurs Chiron and Chariklo also have rings.

In 2017, a pair of researchers theorised that Mars, too, once had a ring. They conducted simulations of the larger of the two Martian moons, Phobos, and found that it could have formed after an asteroid slammed into Mars, sending debris flying into space, forming a ring that then clumped together into an earlier form of Phobos that was much more massive than it is today.

Now this new research has added Deimos into the mix - and the findings are in total agreement with the previous model.

"The fact that Deimos's orbit is not exactly in plane with Mars's equator was considered unimportant, and nobody cared to try to explain it," said astronomer Matija Ćuk of the SETI Institute.

"But once we had a big new idea and we looked at it with new eyes, Deimos's orbital tilt revealed its big secret." ...

But there is something screwy going on with Phobos. It's much closer to Mars, on an orbit of 7 hours and 39 minutes, and it's getting closer to Mars by 1.8 centimetres a year.

Within 100 million years, it's expected that Phobos will reach the Roche limit, the distance from Mars at which the planet's tidal forces tear the moon apart.

Much of the debris could form a ring that rains down on Mars; but some of it could re-form into a smaller, newer Phobos that gets pushed outwards as the ring is pulled in.

This, according to the 2017 research, could have happened several times in the past. And this is where Deimos comes in.

Using numerical simulations, Ćuk and his team attempted to model how such an outward-moving proto-Phobos would have affected Deimos' orbital inclination. And they arrived at a proto-Phobos 20 times the moon's current mass, which would have entered a 1:3 orbital resonance with Deimos at a distance of 3.3 Mars radii that pushed the latter's orbit into a slight tilt.

This neatly produced the Deimos orbit we see today, which then remained relatively unchanged for billions of years. ...
FULL STORY:
https://www.sciencealert.com/the-weird-orbit-of-mars-moon-suggests-the-red-planet-once-had-a-ring

INFO ABOUT THE DRAFT REPORT ACCEPTED FOR PUBLICATION:
https://arxiv.org/abs/2006.00645
 

Mythopoeika

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Newly published research suggests this wouldn't be the first time there was a ring around Mars. For one thing, both the Phobos and Deimos of today may have coalesced from a prior ring - perhaps more than once.


FULL STORY:
https://www.sciencealert.com/the-weird-orbit-of-mars-moon-suggests-the-red-planet-once-had-a-ring

INFO ABOUT THE DRAFT REPORT ACCEPTED FOR PUBLICATION:
https://arxiv.org/abs/2006.00645
That might explain why the moons aren't nice and smooth.
 

INT21

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May not explain the odd 'striations' though.
 

INT21

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But not on both moons.
 

INT21

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I meant that the striations are only on one moon.

Wouldn't one expect them both to be similar.
 

madmath

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Not necessarily. They are different sizes, in different orbits, and may have differing overall compositions. Small differences between bodies can result in very significant differences in behavior over millions of years. Yet another reason to study them more closely.
They'd also make good bases for early human Mars missions, being easier to land on and take off from. Natural observation platforms and way stations.
 

INT21

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Not necessarily. They are different sizes, in different orbits, and may have differing overall compositions. Small differences between bodies can result in very significant differences in behavior over millions of years. Yet another reason to study them more closely.
They'd also make good bases for early human Mars missions, being easier to land on and take off from. Natural observation platforms and way stations.
As envisaged by K M Robinson in his Mars trilogy.
 
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