Phobos, closeup of fear

By Phil Plait | March 15, 2010 3:35 pm

As I promised a little while back, the European Space Agency has released new extremely high-res pictures of Phobos, one of the moons of Mars! Check this out:


Yegads. Click to embiggen, and see this in all its glory. This image, taken by the Mars Express spacecraft, has a resolution of 4.4 meters per pixel, meaning objects about the size of a two-car garage can be seen on the surface of Phobos. For comparison, this lumpy, battered moon (named for the Greek word for fear, a companion to Mars) is 27x22x19 kilometers (16x13x11 miles), so even though it’s on the tiny side, this is still a fantastic map of the surface.

And an important one as well: next year, Russia will be launching a probe called Phobos-Grunt (Phobos soil) that will attempt to land on the moon, collect a sample of its surface, and send it back to Earth! These images of Phobos will help the Russians figure out the best place to land.

On the ESA page linked above, you’ll also find a cool 3D anaglyph of Phobos, and if you want to stay up to date on all this, check out the Mars Express blog, too.

Image credit: ESA/DLR/FU Berlin (G. Neukum)

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

Comments (44)

Links to this Post

  1. Fly-by pics of Mars’s moon, Phobos « Orion Spur | March 17, 2010
  1. If you look REALLY closely you can see the dead Space Marine resting against the lip of the top-left crater.

  2. Ben

    Cool, you can see the UAC Corporation’s ruined base teeming with cacodemons and imps!

    … What? I KNOW it’s there!

  3. Douglas Troy

    It’s sad, really, he was SO close to that Health pack and BFG ammo …

  4. Pareidolius

    Are those lateral trail-like craters where the moon was impacted and then the rock bounced along in Phobos’ feeble gravity before coming to rest (or escaping)?

  5. Bruno

    What’s up with all those parallel-ish striations, and those lines of craters (?), again mostly parallel to each other?

  6. Bruno

    And why do the small craters look so defined whereas the large ones are so smooth? I would imagine Phobos wouldn’t have an atmosphere to even everything out.

  7. Stephen C. Burrows

    Any idea what the striations are? They look like rings or gullys, but so strange.

  8. Bruce the Canuck

    The weirdest thing is that some of the trails cross other trails at an angle. If they’re trails from bouncing or rolling boulders, why so many? Maybe after an impact, a lot material ejected comes back at the moon just below escape velocity and in the low gravity bumps along a very loosely packet surface? But you’d still expect it to stop faster.

  9. Tim G

    Perhaps Phobos is suitable for extracting water for use as a propellant in nuclear propulsion systems.

  10. I can’t find the garage, Phil. ūüėČ

    Did they discover anything about the supposed spongiosity of it?

  11. Phobos-Grunt? Seriously? Oh, man, I want one of their project T-shirts.

  12. Bigfoot

    Figure out the best place to land?!! That’s easy — you land where the Leather Goddesses are!

  13. XMark

    Where’s the monolith?

  14. Mike from Tribeca

    I don’t usually go in for the “awe thing,” but this one has me doing the awe thing in triplicate. With a thick dollop of awe on top.

    Oh, and thanks Bigfoot for bringing back those golden Amiga memories with your mention of Leather Goddesses! Very funny.

  15. James

    It kind of amazes me how we can land stuff on places like this even when there could be, say, a one-car garage right in the middle of the landing spot, and we wouldn’t see it (thanks to the time-lag) until after the probe had crashed right into it.

  16. gss_000

    “Phobos-Grunt? Seriously?”

    Yeah. Amusing for us English speakers.

    The politics of the mission is fascinating, too. It’s carrying a Chinese spacecraft that will go to Mars and they are *pissed* at the Russians because technical reasons dealing with the dual payloads and the rocket that will launch them delayed the launch by 2 years.

    IIRC the Planetary Society also has a payload that will test the panspermia theory. There were some contamination issues with that that I think have blown over.

  17. ND

    Good luck to Russia (and the Chinese) on their mission. They really could use a break from stream of bad luck with Mars. Any successful mission is all the better for all of us.

  18. tacitus

    I believe the Phobos-Grunt team already has an eye on the landing zone — the smooth area above the double overlapping craters at the bottom of the image, somewhere to the left of the tiny bright crater in that vicinity.

  19. Chip

    For an artificial satellite built by advanced aliens it sure is kinda lumpy. (Or is that deliberate just to fool us?)

  20. XMark

    Well, presumably the Martians died billions of years ago when Mars lost its water. So over that time dust accumulated on the Satellite. And the high-tech cities on Mars were buried under dust as well.

  21. The hi-res photo shows a lot of the craters are askew on one side as if the impactors struck Phobos at a very low angle. This suggests the “sputtering” trails, mostly moving from upper left to lower right, were from impactors hitting at such a low angle they skipped across the surface of Phobos like a flat rock skipping on a pond, losing more mass with each impact until they finally stopped.

    The fainter and highly parallel banding could be a feature of the original rock mass rather than from meteor impacts. On Earth this would be a sign of differential weathering, where one layer of rock is slightly more resistant erosion/weather than the layer immediately below it and so one layer “stands out” in higher relief.

    Assuming Phobos is made of igneous rock, one thing that could cause banding like this is magmatic segregation, where the original rock is molten and cools slowly enough to allow the various minerals to separate into layers. This would suggest that Phobos was originally part of a much larger object, which would be required for the molten rock to cool slowly enough to chemically separate. If Phobos was, as some suggest, a big pile of loosely aggregated material fused together by impact without any further evolution, it would be hard to explain the origin of this banding and layering, since there should not be any order or arrangement to the aggregation.

  22. Oh … the “erosion” that would occur on Phobos would be from micro-meteorites. The effect of this type of erosion can be seen on the craters, where the smallest and youngest are very crisp and sharp and the older ones are soft and rounded. 4 billion years without an atmosphere and being constantly pelted by tiny particles going a few miles per second can do a lot to dull a once-sharp rock. If the original bedrock of Phobos is banded and some bands are slightly more resistant to erosion than others, differential weathering from micro-meteorite impacts could create these parallel striations.

  23. Dave

    To put it in perspective a little more for some of us… So Phobos is a little larger in cross section than… Washington DC! Well, the original city, including what’s now Arlington VA too…

    Lay it on top and, let’s see, Dupont Circle would be about here… and oh, there’s the Tidal Basin… and there’s Anacostia… and the Pentagon…

    Not that I’m advocating anybody should try laying Phobos on DC…. though if Russia is going to send a probe there… ūüėČ Hey, just kidding, it’s my home town! (DC, that is, not Phobos! Nothing against Phobosians, Leather Goddesses or otherwise…)

  24. jcm

    “Click to embiggen” should have been “Click to emphobiate”.

  25. “Click to Thoatify”?

  26. Dr Cy Coe

    I like the way the Russians named the mission. Says right what its about. No focus studies needed to created mass media friendly (convoluted) acronyms. It’s going to Phobos and it’s got to do with its soil.

  27. #16 gss_ooo:
    You recall correctly. The Planetary Society, of which I’m proud to be a member, does indeed have an experiment which is due to fly aboard Phobos-Grunt. It is indeed intended to test an aspect of the panspermia theory, i.e. to test whether microorganisms can survive for extended periods in the environment of space. ( We already know that some can, as living microbes were found on Surveyor 3, when parts of it were returned by the Apollo 12 crew, after over two years on the Moon. )
    The experiment contains sealed samples of a number of different microorganisms, which will be returned to Earth together with the Phobos samples, to see whether, and how well, they have survived.
    I’m not aware of any contamination issues, as the sealed ceramic casing of the experiment has been extensively crash- and destruction-tested; it should survive intact even if the rocket explodes on the launchpad.

  28. Tiny moon is tiny, but so very cool.

  29. Joe Meils

    Strange. We get these marvelous views, and all people can talk about is what unfortunate name the russians have given their upcoming probe…

    What amazes me about Phobos, (and indeed many smaller bodies like this) is just how relatively smooth the surface area is. Yes, there are groves and craters… but overall, the surface seems like it started out as being fairly uniform. You would think that a small object like this, without the gravity to pull itself into a sphere, would look more like a rough collection of crags, and lumps held together by common gravity…

  30. BigBob

    These pics are impressive, but my favourite comes from an earlier mission. So for Phobos lovers out there, can I suggest you search for an image called:
    it’s big and beautifully lit and the grooves on the surface are just … matchless. This image is currently centred on my desktop.
    The current theory is that the grooves were etched by debris thrown up by massive impacts on the surface of Mars. I had a model in mind some years ago built out of imagination one evening. Suppose you take a ball, about the size of a Rugby ball, (or a foot ball for those regions that substitute others games for Rugby) and place it, pointy end up in a transparent tank of oil. Now take some tiny ball bearings, the smaller the better, and drop them into the oil such that they roll or tumble down the outside of the ball. That pretty much describes my understanding of the origins of the grooves; debris thrown up from the Martian surface, leaving their tracks on Phobos as they roll and bouncealong its sides. The fact that there are a number of different families of grooves from different events suggests that Phobos’ leading end was not always so.

  31. Danno

    Is it correct to use the term “soil” here? I generally consider soil to have organic content, whereas regolith is composed of loose debris caused by meteorite impacts. Would it be better to refer to the soil as regolith, or am I just getting my knickers in a bunch for no good reason?

  32. Zippy the Pinhead

    The only thing we have to fear is fear itself … and Phobos!

  33. davem

    Is it possible that the multiple parallel trails are the traces of objects formerly lying on the moon’s surface, that have all been disturbed simultaneously by the moon colliding with something? Then BigBob’s theory looks a goodun’, and explains why thre are so many trails. The chance of them all being the result of oblique collisions is close to nil, given that all other objects seeem to have hit smack on.

  34. Pat Harris

    I too noticed the parallel lines.

    It almost looks like a huge chunk of sand stone with craters!

    Fabulous picture!

  35. PhilG: thanks for the link re: the parallel striations. That explanation makes sense.

  36. One of the most interesting questions about Phobos and Deimos is why Mars, of all the rocky, inner terrestrial planets, has these tiny rocky satellites and Earth, Venus and Mercury do not. Why don’t they? Why only Mars?

    There’s speculation that the orbits of both Phobos and Deimos are decaying and they will eventually skid on to Mars, creating gouges like the Valles Marineris. If Earth, Venus or Mercury had similar tiny moons that crashed long ago, the gouges they made should still be easily visible. So why Mars?

  37. nomuse

    So when do we get a picture of the third moon……Bottomos?

  38. Ares

    The names of Mars’ moons come from Greek mythology and specifically Hesiod’s cosmogony. Phobos and Demios were Ares’ sons from Aphrodite. Even though they both were his companions in war that was a result of them being his sons.

  39. Pi-needles

    17. ND Says:

    Good luck to Russia (and the Chinese) on their mission. They really could use a break from stream of bad luck with Mars. Any successful mission is all the better for all of us.

    Even a Russo-Chinese mission to put a giant death ray laden battle-station into orbit above America? ūüėČ

  40. Keiko

    Why is it that the smaller space objects seem to be more battered than the much larger ones? Earth has its craters, but most of its deep features appear to be erosion based. Is our planet’s power of erosion so great that it could cover up almost everything that’s hit it?

    Are most of the wounds on moons from a time long ago, before Earth even began to be hospitable to life?

    Too many questions, not enough space probes.

  41. BigBob

    davem @34 wrote:

    Is it possible that the multiple parallel trails are the traces of objects formerly lying on the moon’s surface, that have all been disturbed simultaneously by the moon colliding with something? Then BigBob’s theory looks a goodun’, and explains why thre are so many trails. The chance of them all being the result of oblique collisions is close to nil, given that all other objects seeem to have hit smack on.

    I’m sorry for the delay davem and you probably won’t read this but it’s just occurred to me that there’s a factor you may be unaware of.
    Phobos (and as it happens Deimos too) is tidally locked with Mars, that is to say it always shows the same ‘side’ to Mars just as our Moon always shows the same ‘side’ to the Earth. So tidally locked moons rotate once on their axis for each orbit around their planet. That means Phobos has a leading face and a trailing face as it orbits Mars. So if the current theory about the grooves being caused by debris thrown up from massive impacts on Mars is correct, that explains why the many grooves are in parallel. The rocks that drew the lines would not have had to arrive all at the same time. Even if Phobos encountered a rock in its path today, it would still roll the rock along its flank and the groove that it made would be in parallel with hundreds of existing grooves. The fact that there are other ‘families’ of grooves on Phobos suggests that it used to be oriented differently, when its leading ‘face’ was not that part of the surface that leads today.

  42. James Harmer

    Keiko, the amount of geologic activity that a body posesses is directly proportional to it’s size. The bigger it is, the more heat from radioactive decay is trapped inside by the insulating bulk of it’s own mass. This causes more vulcanisim which resurfaces the exterior and so fills in craters. Because Earth has an atmosphere and liquid water it also has plate tectonics which continualy recycles the surface, again removing craters.
    You are correct in thinking that most craters were formed long ago. The early Solar System had a lot more rubble and debris floating around than it does now and impacts were more common. This culminated in a period called the Late Heavy Bombardment, about 4.1 to 3.8 billion years ago, during which the inner planets were extensively pummeled until things quietened down to the more peaceful conditions we enjoy today.


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