back to article 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 …

  1. Your alien overlord - fear me

    Doomed, we're all doomed. Oh hang on, we're not living on Mars yet are we?

    1. PleebSmash

      At that rate, we could colonize Mars within the next hundred years, strap some ion engines onto Phobos, and stabilize the orbit indefinitely. Then use it as a launch pad or space elevator type of thing.

      1. Vulch

        Deimos is a better bet for a Martian space elevator, Phobos gets in the way though...

        (Fountains of Paradise - Arthur C Clarke, Red/Green/Blue Mars - Kim Stanley Robinson)

    2. Tony Haines

      The earth has a solid iron core which is growing at about half a millimetre per year. Obviously this can't go on indefinitely.

      Something for you to worry about?

    3. Kharkov
      Thumb Up

      @ 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...

      1. Adrian Midgley 1

        You think solid rock is easier to mine

        than crunchy powdery stuff loosely held together?

        Removing it from the elevator path might be the way to go.

  2. Big-nosed Pengie

    That's three spellings of the moon's name in one article. Would you care to try for four?

    1. Anonymous Coward

      Gonna need more names...

      Well, what about a name for the orbital ring which Phobb... uh, whatever, will turn into, some 30M+ yrs hence?

      Since it will probably be viewed from the surface of a terraformed Mars, how about "The Phobow?"

    2. Richard Chirgwin (Written by Reg staff)

      Blah, thank you, I'll take care of that now.

  3. et tu, brute?

    Phobos won't survive that long!

    According to the future history as described by Robinson in Red Mars, it will come down much earlier, when Nadia punches out the special code to ignite the burners installed by Arkady... roughly in 2062!

    1. AbelSoul

      Re: Phobos won't survive that long!

      I could've done with a spoiler alert there, et tu!

      I'm about three quarters of the way through Red Mars but haven't reached that part yet.

      Ah, well. Never mind

      1. et tu, brute?

        Re: Phobos won't survive that long!

        Sorry AbelSoul!

        Thought everybody had read the whole trilogy already... should be compulsory reading in school, if you ask me!

    2. Sandtitz Silver badge

      Re: Phobos won't survive that long!

      According to the future history as described by Joe Haldeman in The Coming, Phobos will first be split in two roughly during Christmas of 2054, shortly before the aliens arrive...

  4. Adrian Jones

    Won't somebody think of the Leather Goddesses?

    1. Paul Crawford Silver badge

      I often do! But usually at night. With a tube of lube to hand.

  5. chivo243 Silver badge

    Call me ignorant...

    Not an astroboffin, but don't you have to have tides( water/liquid) to have tidal influences?

    1. Jimmy2Cows

      ....don't you have to have tides( water/liquid) to have tidal influences?

      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.

    2. tony2heads

      Re: Call me ignorant...


      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.

      1. Richard Plinston Silver badge

        Re: Call me ignorant...

        > 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.

    3. Brewster's Angle Grinder Silver badge

      Re: Call me ignorant...

      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.

  6. This post has been deleted by its author

  7. chivo243 Silver badge

    @ Jimmy, Tony and Brewster

    Thanks for the intelligent replies, I strive to learn something new everyday, job done. Up votes all around!

  8. davidp231

    Well that's the Mysteron problem sorted.

  9. Chris Evans

    Size, tides and despun?

    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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