Mars in about 50 million years... Water again for a brief period?

[KerikBalm]

So, the evidence for water on mars at some point in the past is obvious.

Theoreis/hypothoses posit a variety of durations and conditions for when there was water.

In some, water existed transiently after large eruptions, or impacts (particularly backed up by craters that seem to be surrounded by mudflows)...

And in ~50 million years, there may be a rather large body impacting Mars,

Its moon Phobos:

http://en.wikipedia.org/wiki/Phobos_(moon)

"Due to tidal interactions, Phobos is drawing closer to Mars by one meter every century, and it is predicted that in 50 million years it will collide with the planet or break up into a planetary ring."

I wonder if Mars had more caputred asteroids in the past, and its moons in unstable orbits would impact and cause periods in which there was liquid water on mars.

Anyone with some program like Universe Sandbox, or just some good knowledge and logic, care to take a guess what would happen if Phobos started to dip too low into Mar's atmosphere and deorbited into Mars?

It won't hit the polar ice caps, thats for sure, but there do seem to be large amounts of near-surface ice.

[sndrtj]

I imagine Mars having flowing water somewhere in the next 50 million years, but not because of Phobos; probably we humans will do the magic trick. Phobos will just pass its Roche limit in 50 million years; that doesn't mean it will crash into Mars in one single piece. Passing the Roche limit means that it will loose its own cohesion, and be pulled apart in several fragments, or possibly a ring structure. These fragments might or might not eventually hit the surface, but it's unlikely Phobos will come crashing down on Mars in one single piece.

[Nuke]

if we colonize mars it may be worth it to us to artificially boost phobos to a higher orbit. perhaps using a gravity tractor. we could also end up strip mining it, and then dropping the remaining bits into the atmosphere artificially to heat the surface for terraforming.

50 million years is a really long time.

[sndrtj]

Actually, in Kim Stanley Robinson's Mars Trilogy, Phobos is artificially deorbited to prevent it being used as a weapons platform. In any case, Phobos won't come crashing down as hard as an asteroid from interplanetary space would. If we could artificially deorbit it, I'd opt for crashing it on the southern pole (yes, that requires massive change in inclination), as that would release large quantities of frozen CO2, which would heat up the planet on the long term.

[KerikBalm]

Phobos will just pass its Roche limit in 50 million years; that doesn't mean it will crash into Mars in one single piece. Passing the Roche limit means that it will loose its own cohesion, and be pulled apart in several fragments, or possibly a ring structure. These fragments might or might not eventually hit the surface, but it's unlikely Phobos will come crashing down on Mars in one single piece.

According to this, it already has passed the roche limit:

http://burro.astr.cwru.edu/stu/advanced/mars_moons.html

"For Mars-Phobos, the Roche Limit is estimated as 10,800 km. However, Phobos is about 1400 km inside of this. This is because the Roche Limit does not take into account the strength of the material of the object."

So, if Phobos were simply a "rubble pile", it should already be coming apart.

But a sinlge large monolith would not be torn apart. Without knowing in detail what the internal structure of phobos is... it may still remain in 1 peice.

The 50 million year figure is based on its rate of decay until it encounters the atmosphere (or at least the part that is thick enough to rapidly de-orbit it), no?

50 million years is a really long time.

For us... yes... but in the grand scheme of things? no

Life has been here on earth for nearly 4 billion years.

Life will be here on Earth in 50 million years.

If phobos doesn't break up... could it lead to period of another wet Mars?

[rodion]

it seems very unlikely to me that phobos would ever naturally fall to mars as an impactor, its composition is far too gravelly and mars' tidal influence will break it apart into a ring system long before it decays to the point that it could hit the planet. phobos has a density of less than 2g/cm^3 so we could also rule out any sort of dense core that would survive mars' tidal effects. a possibly more realistic question to ask would be what effect the energy carried by an excess 10 trillion tons of material steadily entering the martian atmosphere over a period of [some number i don't know] years might have on martian surface conditions, but i don't have any frame of reference to determine if it would be particularly dramatic.

[Motokid600]

Idk if 50million years is enough, but as our sun ages... Would it be safe to say that Earth and Mars would switch roles? Earth would become a desert planet and Mars would essentially thaw.

[Skyler4856]

I wonder how hard it would be to utilize lasers to heat the martian caps.