Feeble Phobos flaking as it falls to Mars Mars' larger moon, Phobos, is already showing signs of the structural failure that will one day mean it breaks up, according to boffins from NASA Goddard. The finding, announced here, was presented to November 10's annual Meeting of the Division of Planetary Sciences of the American Astronomical Society in Maryland. Goddard's …
@ Your alien overlord - fear me
Thanks to you, I now have the (wonderful, take an upvote, sir) mental image of the first colonist stepping foot on Mars, falling to his/her knees and howling to the sky, "Dooooomed! We're all doooomed!"... Well you can see it, can't you?
Worse is the news that Phobos isn't even (mostly) solid rock. There goes our orbital spacestation/zero-g manufacturing center...
No. Tidal. Not tides.
Tidal forces refers to the effects on Phobos structure due to differing strength of Mars' gravity between points on Phobos closest too and furthest from Mars. The closer bits feel Mars' gravity more strongly, and so are distorted more, than those further away. This puts the moon under strain.
NOPE
Solid earth tides also exist. They are of order 10's of centimetres (rather than meters) . They have lower amplitude and are not in phase with the ocean tides, because the continents are just floating on magma.
Even rock will flow if warmed enough and given enough force.
> Solid earth tides also exist.
You may also note that also there are effects of centrifugal forces. The earth bulges at the equator because of the rotation of the earth but this is not the whole story. The Moon does not rotate around the Earth, they both rotate around a common CoG which is not the centre of the Earth but around 5000km towards the moon (still inside the Earth). As the Earth spins on its axis the surface (or indeed everything) experiences a changing amount of centrifugal force from the Earth-Moon rotation. This is in addition to, or subtraction from, and is often in a different direction to, the gravitational pull of the moon. The total nett centrifugal force of the Earth-Moon rotation is equal to the total gravitational pull of the moon but the distribution is quite different.
The forces that create the ocean tides apply to everything. They're most obvious on large bodies of water, but the rock in the earth experiences "solid earth tides", too. There's a variation in height (distance from the centre of the earth) that can approach a metre. And there are slightly smaller east-west, north-south displacements too.
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Including its size in the article would have been useful!
"Phobos is a small, irregularly shaped object with a mean radius of 11 km"
Also when trying to understand tides it is important to know if the moon is despun like Earth's (i.e. the same face of the moon always faces Earth.)
From Wikipedia I've found:
Rotation period: Synchronous
I read that to say it is despun so I'm not sure how the Phobos has tides, unless Mars has significantly irregular gravity! Which I wouldn't have expected.
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