Phobos ahoy!

By Phil Plait | March 2, 2010 2:15 pm

Over the next few weeks, the European probe Mars Express will be making a series of close passes to the Martian moon Phobos, a wrecked potato that has had an extensively battered history. In January, ME got this shot (among others):


You can see that this little moon has been kicked around quite a bit. Those parallel grooves are still a bit of a mystery; they are most likely cracks that formed when Phobos got whacked, creating the 10-km-wide crater Stickney on one end, but that matter is not 100% settled. Maybe these new observations will help end the debate. [UPDATE: Commenter Big Bob points out that the cracks are most likely not due to the Stickney impact! I haven’t kept up on my Phobos groovy research, obviously. Also, in the next bit I say more images are coming, but in fact this close passage of Phobos will not yield very high-res pictures, because this flyby is to measure the gravity field around Mars, and the other instruments — including the cameras — must be turned off. Oh well.]

And as nice as this image is, we’ll be getting lots better ones soon! So this is a heads-up: closest approach is on March 3, so stayed tuned for more pictures. I’ll post ’em as I see ’em.

CATEGORIZED UNDER: Astronomy, Pretty pictures
MORE ABOUT: Mars, Mars Express, Phobos

Comments (42)

Links to this Post

  1. » Blog Archive » Phobos, closeup of fear | March 15, 2010
  1. David

    Naturally, the grooves are an ancient audio recording, like a wax cylinder.

  2. Does Phobos have a “leading” edge, like Iapetus? If so, how are these grooves oriented with respect to the leading edge?

  3. What David said. Quickly, get in touch with Hoagland! He’ll be able to tell us what the recording says!

  4. Hold on, I’m running it through my interpreter now.

    It says…

    “Mary had a little lamb, its fleece as white as snow.”

    Now, can someone get me a good image of Deimos, so I can see what the rest says?

  5. David

    Ken Copeland preached once that the bible told him why there were “canals” on Mars. Maybe he knows about these grooves as well. Funny that he never actually said what the canals were for, though.

  6. Brian

    No no no. You need to play it backwards:

    “Devil bunnies! I snort the nose, Lucifer! Banana! Banana!”

  7. KAE

    I remember when Carl Sagan was on the Tonight Show with Johnny Carson. He was talking about the naming of that crater on Phobos. That’s where I first heard the name ‘Angeline Stickney’ – the wife of astronomer Asaph Hall, who discovered the two moons of Mars.
    I love the sound of that name and I can still hear Carl Sagan pronouncing it in my mind.

  8. Bigfoot

    They don’t look very crack-y to my untrained eye. Wouldn’t cracks be more oriented in a radiating pattern, at least some of them? I know that smarter minds have already applied themselves to this, and I am not questioning their thought processes, but that pattern of linear features boggles the imagination.

  9. Charles

    Funny. It looks like differential etching. As a metallurgist, I’ve seen it both unintended (when metal things corrode) and intended (when etching a specimen, which is really just applied corrosion). Comes from bands of compositional gradients that arise from manufacture.

    But those are usually parallel. Really parallel. These cross a little. But maybe things the size of Manhattan might have a little more variability than things the size of a human hair.

  10. Ian

    What do you make of this Phil:

    600 million tons, but how easy is it likely to be to actually extract it?

  11. Nemo

    It looks like Phobos was rolled over something. Something scratchy.

    Actually, more like something rolled around it.

  12. Douglas Troy

    Those trenches are obviously caused by the Giant Phobos Moon Worm.

  13. Charlie Young

    I’m guessing it’s Big Foot making dust drawings. Either that or someone is up there plowing grooves in the surface.

  14. Tensor

    They look like glacial striations, but it can’t be.

  15. That’s one battered moon. I can’t wait to see the new picture sets…

  16. drow

    they’re crop rows, left by ancient martian farmers. the canals had to go somewhere, right?

  17. Kevin F.

    I’ll wager the grooves are from the ejecta from impacts finally settling in after orbiting for a while.

  18. bigjohn756

    Phobos looks like a potato that went hunting with Cheney.

  19. Mike C.

    Most interesting info, and a cool photo to boot. Which reminds me to go out and pick up some potatoes.

  20. Quick question.

    What is the correct pronounciation of Phobos? I had always assumed it was “PHO-bose”, but I am currently listeing to KSR’s Red Mars on Audiobook and the narrator pronounces it “Pho-BOSS”.

  21. Steve Paluch

    I thought the flyby on March 3rd was to map the gravity field, not take pictures…

  22. Those look like cross beds. Unfortunately Phobos is too large for them to be cross beds, but how cool would it be to have an ejected rock with flow structures on/in it??

  23. I'd rather be fishin'

    When I first saw the striations, it reminded me of claw marks on my leg left by my daughter’s cat.

  24. kevbo

    You forgot to remind us to check out the full size original image (i.e. click to enspudify)…

  25. no, no, no – it was stuck in giant Rotato! (edit: If you’ve ever used a Rotato, the grooves DO look striking similar :) )

  26. locke

    @Steve Paluch, you’re correct, of course. There will be at least one other close flyby soon afterward to take more images.

  27. b2

    The old images set me thinking again about the grooves. I worried about them for months a few years back. Now I’ve had a new idea. The trouble with the ploughing through debris theory [John B Murray 2006] is that at orbital altitude there won’t be strings of ejecta narrow enough to make those regular grooves, it has to involve some fine ring material. But if Phobos is orbiting in a ring it have the same velocity as the ring material in which it orbits, it won’t be ploughing through anything. So here’s the new idea. If, during the period when Mars had these putative rings, Phobos had a highly elliptical orbit, but in the same plane as the ring’s circular orbit, it would have come screaming in and ploughed right through the rings at periapsis on each orbit. It would have had to be tidally locked as it is now, to present the same face to the flak, though it must have wobbled a bit, going by the angles of the grooves. (cf. Murray)

    Perhaps the rings even formed in the same event that created Phobos, impact or capture, presuming there was enough material dislodged by the tidal disruption if it was the latter.

    I understand that the orbits of smaller particles and dust cicularise and flatten out relatively quickly by collisions, while a large chunk like Phobos, would slowly circularise by tidal forces, so if they formed together there would be a time when the orbits were different. Another point is that a common source for Phobos and the rings would be most likely to put them in the same plane.

    The involvement of rings of fine material is crucial. How else could a groove form that extends the length of the flank in serene uniformity, than with a narrow linear obstacle like a ring edge on? There are some less well defined grooves that are clearly crater chains, like the five little craters almost identical in size, equally spaced in a line parallel to one of the huge smooth trenches. These could have been caused by irregularities in the rings, bits where larger and fewer ring particles accumulate.

    Does it have any merit?

  28. BigBob

    The notion that the lines emanate or even radiate from crater Stickney was pretty much put to bed a couple of years ago. Here’s a paper from 2006 describing the appearance of different ‘families’ of grooves, that were caused by separate events.

    Here’s an abstract from the Open University paper on evidence from HRSC Mars Express:

    It says (amongst other things);
    ‘A new map of Phobos’ grooves shows their orientation to be quite independent of Stickney crater, and the evidence is now overwhelming that the grooves of Phobos were caused by debris ejected from a large impact craters on Mars’.

  29. Grand Lunar

    Makes me think that going to Phobos as part of the Flexible Path is definately worth it.

  30. Charles

    I can’t get past preferential erosion, possibly by micrometeoroids (maybe? I’m not an astronomer), but it would require Phobos to have layers of different rock (some harder, some softer) normal to the NW-SE axis (in the above picture). Like looking at the walls of the Grand Canyon. Problem is, I can’t for the life of me figure out how a moon could have been carved out of solid rock and placed into orbit without getting melted. If it was a capture, it still would have to have come from a much larger body (big enough to form rock layers) which was destroyed without melting Phobos.

  31. Charles Boyer

    Phobos is a captured asteroid and not an accreted moon, correct?

    And if memory serves, it falls roughly 1.3 meters towards the Martian atmosphere every year and that soon (from an astronomical standpoint) it will enter the atmosphere and impact somewhere on the red planet.

  32. rob

    ah, dang. critter42 beat me to it.

  33. James

    Those marks are definatly not cracks. I would say objects in the moon’s path have been dragged across it, forming the groves. It must either be made of quite a soft material or the process has been going on for a very long time.

  34. DreamDevil

    NASA should be careful so they don’t accidentally open the portal to hell.

  35. That is one Groovy Moon.

  36. Corey

    We must declare Martian Law! Sir Deimos! Sir Phobos! To me!

  37. Gary Ansorge

    It’s obvious the Martians of John Connors time dragged a bunch of asteroids into orbit, outfitted them as generation ships and left for a better world. Far from here. Since the MArtians had to leave while earth was still too turbulent to support their life forms. They finished up with a couple of small ones left over, so we have partially worked generation ships left behind,(hollow, right?),,,Phobos and Deimos.

    Can’t wait to get there and verify this,,,or not,,,

    GAry 7

  38. It looks like it ran through debris field and got all scratched up.

  39. Spyre

    I’ve seen these types of grooves before. It took me a while to recall just where. I’ve finally remembered that I saw grooves like this on some potatoes I dug up. Asking around the agrarian community, I learned they were caused be a particular worm that loved to burrow shallowly into spuds whilst they’re underground. Obviously, they do this to make people wonder why there are groovy potatoes.

    Ergo, ipse dixit and QED, it becomes apparent that Martian Potato Worms crawled up onto the Face of Mars, became lodged in the nose and were subsequently sneezed into orbit where some number of them managed to swim onto Phobos, having mistaken it for a really large and succulent Russet.

    Mystery solved.

    No. No thanks are needed; it is my humble joy to commit a priori anywhere I can.

  40. ranti

    ha ha ahhhhh ahhhh,,, the orbit of phobos is just like our satelites. very low and fast. nothing like it on the solar system, all the moons around the other planets including ours are far from the surface and slow. the russians are very interested and will land a rover soon. this thing is not solid. Mars was like our planet 65 million years ago, a blue marble. this thing may have been hit by asteroids for that long. phobos has the orbit of a satellite, not consistent with a natural satellite. or it could be a captured asteroid. It is also slowing down and will crash into mars in just a few hundred thousand years.

  41. Binky the Inquisitive

    Obviously the extinct Martians wrapped this whole thing crudely with cable a billion years ago in an attempt to use it to generate power as the huge coil orbited through the Martian (and solar) magnetic fields. You can see the traces of different layers of windings going different directions. Most likely it didn’t work very well. We are looking at an all-time engineering f*-up, here. Probably funded by Martian tax dollars. Hence why they didn’t survive. The ancient Martians were incompetent.

    Either that or they were trying to build a gigantic, planet-wide orgasmatron. Maybe it did work, and after that they didn’t bother to reproduce anymore… same result. Oh well.


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