Phobos up close and very personal

By Phil Plait | April 9, 2008 6:00 pm

Mars has two dinky moons, Phobos and Deimos. Phobos is the bigger of the two, and is about 22 kilometers (13 miles) across. There have been hi-res images of Phobos taken in the past, but none like this!

That’s the creepily good HiRISE camera from the Mars Reconnaissance Orbiter, of course, that took the image. Click it to embiggen and get much higher-res versions: the raw data has a resolution of 7 meters per pixel. That’s smaller than a house. There have been more detailed images taken in the past, but these collected more light from the tiny moon and so have better quality.

The detail is remarkable. The image is false color, and blue may represent fresher material.

The crater Stickney on the right is huge compared to the moon; if the impactor had been any bigger or moving faster it would have shattered the moon. The long parallel grooves were probably formed as stress fractures in the impact. Check out the awesome image of the crater itself. Wow.

And if that’s not enough, pull out your red/green glasses and take a gander at the 3D anaglyph they made. The tiny craters really stand out… uh, I mean, stand in. Whatever. They’re cool, so take a look.

And do it while you can. Eventually Phobos will crash into Mars, and that’ll be that. Chances are that by then we’ll boost it to a higher orbit ourselves (it makes a handy base), but still. Coolness prevails on Mars.

Hat tip to BABloggee and HiRISE guy Timothy Reed, who tells me he "lovingly installed and aligned all the optics".

Comments (41)

Links to this Post

  1. Science Doesn’t Sleep (4.10.08) | Beyond Bones | April 10, 2008
  1. Cello Man

    So, where is the crate with the chainsaw hidden?

  2. Sili


    Craters within craters.

    So purdy.

  3. BaldApe

    Are the grooves connecting the craters in the top right (and other places) caused by ejecta from the big crater rolling and bouncing after the impact? They seem to radiate from it.

    I know Phobos doesn’t have very much surface gravity at all, but that’s what they look like to me.

  4. Yoshi_3up

    Argh, I only have cyan-red 3D glasses.

  5. If you look hard enough, and long enough, and smoke enough mushrooms, that bluish area starts to kinda look like Jesus…. Or maybe one of the guys from ZZ Top. Hard to say.
    Speaking of pareidolia….

  6. tacitus

    Actually, Emily over at the Planetary Society blog talks about a paper that theorizes that the groves were made by Phobos running into debris from asteroid impacts on Mars:

  7. Jeffersonian

    So, if you were able to stand on the surface, would it fell like standing on a giant beach ball, with all horizons quickly curving out of sight? Due to the small diameter and low gravity, could you potentially bounce-hike west for a couple hours and end up right back where you started? Man, that would be cool and visually mind-bending, given the view of Mars, etc.

  8. So, where is the crate with the chainsaw hidden?

    Nah, it’s sitting on a pedestal in the second or third level, you’ll have to hit a button to bring it down, then just shove it in the eye of a Cacodemon. :D

  9. Dallas

    “if the impactor had been any bigger or moving faster it would have shattered the moon.”

    Do objects this big actually shatter, or do they more so melt and deform? I know large chunks can some times come off, but does the entire object really shatter?

  10. BaldApe


    Very cool. Thanks

  11. dave

    I dunno, that moon looks awfully hollow and fake to me. Maybe the rumors are true.

  12. complex_field

    That face-on-mars guy will be all over this like flies on ___. Of course! The parallel lines are not, in fact, stress fractures! They are alien agrarians.

  13. eddie

    I see ancient ruins.

    RCH, where are you?

    Oh yeah, still on Mercury….

  14. The BA says: “The tiny craters really stand out… uh, I mean, stand in. Whatever. ”

    Turn the picture upside down. Then they’ll stand out.

    - Jack

  15. revmonkeyboy

    A very nice picture. You just have to love the resolution of HIRISE. Very nice picture of a rocky, lumpy moon.
    Thanks for the post, I enjoyed it greatly.

  16. Michelle

    Oh my. That’s such a great picture!

    A tiny tiny moon but it’s so fascinating anyway.

  17. Fauxnetikz

    These pictures are fake! If they were real, there would be stars showing in the background! Clearly I’m an expert and have just proven that the whole Mars Reconnaissance Orbiter thing is a hoax.

  18. It’s cool to think that if there was a UPS truck parked there it’d be visible as a brown pixel!
    Way frakin’ cool!
    Rich in Charlottesville

  19. Bruce

    Silly scientist!
    That’s not Phobos.
    It’s a prop from the 7th Star Wars movie, of the Death Star after a really ferocious Rebel attack.

  20. Dr. Al McEwen, the man behind HiRISE will be a guest speaker (along with BA, Carolyn Porco and others) at Spacefest 2009. BTW, those parallel grooves are affectionately called “stretch marks”

  21. kvenlander

    What amazing pics. Thanks to Timothy Reed and all the people in the team for getting those optics out there so we can ooh at the results! I’m afraid my kids are growing up a bit blase about all these fantastic images of other moons and planets nowadays…

  22. Mark Hansen

    These are really great images.
    BTW, has anyone noticed that the “BA, isn’t this supposed to be an astronomy site?” crowd haven’t come around and thanked Phil for giving them what they wanted?

  23. HvP

    For those of you without 3D glasses (like me) you can make a cross-eye pair out of the anaglyph if you have access to Photoshop or similar photo editing software. Just load it into your photo program, split it into seperate RGB channels, discard the green channel and line up the red and blue channels side-by-side. You will probably need to reduce it in size to view it comfortably, but just cross your eyes until they overlap in the center. If it doesn’t “pop out” right then you have them on the wrong side.

  24. Giffy


    I doubt I will be, but I really hope I am alive to see that happen.

  25. Nigel Depledge

    That’s a very nice pic. Thanks once again, Phil, for bringing it to our attention.

    Oh, yeah, and… [rant mode]How come you post all this stuff about astronomy!?!?!?? I thought this was supposed to be a site about religion and politics???!!! !!!![/rant mode]

  26. Sanity

    Dear Martians:

    Our moon is bigger then your moon! nananana!

  27. Martians

    Dear Sanity,

    We’ve got two, you have only one! nananana!

  28. Chris CII

    @ Jeffersonian :
    With a gravity less than a thousand of earth’s, you’d have to be pretty careful about ‘bounce-hiking’ not to fly off into the void. But with 70 km (45 mi) round-trip it would be quite easy to ‘circum-bounce’ the moon in a few hours.

  29. Jupiter

    Dear Sanity and Martians:

    Pipe down you two.

  30. J. D. Mack

    Did you mean “red/blue glasses”? I have a pair of red/blue glasses, and they worked fairly well with the anaglyph.

    I also like the paraedolia effect on the anaglyph image. Kind of looks like a cartoon character.

    J. D.

  31. @Fauxnetikz: It is fake because of no stars? How silly.

    The real reason it’s fake, is that it looks like it’s made in the 3D program Maya, therefore it is made in Maya, therefore it is fake.

    And it would be no problem to put stars in Maya. Which proves… that uhm, that it’s even more fake!

  32. Michelle

    @Bruce: Are you kidding? That’s way too small to be the death star! Silly you.

  33. RL

    How much bigger (compared to today’s rockets) would a rocket need to be to move Phobos to a better orbit??? And do you really think we would do that given the alternative to watch an astronomical event like Phobos breaking up and falliing into Mars?

    And would that cause a big enough impact to eject material towards Earth again? This kind of event would be very interesting to observe a lot of these theories (Roche Limit, Parts of one planet ejecting and hitting another, etc). Yes, evidence does exit for all of this but it would be even more remarkable to observe this kind of thing directly.

    Unfortunately, this won’t happen for 30-80 million years! Maybe it will be passe by then.

  34. wÓÒ†

    That’s no moon. It’s a space station.

  35. AJ

    I’m not a doubter, but I find it amusing how much this looks like a bad computer rendering.

    Of course, it’s because of the simple lighting. There’s no ambient, and with no atmosphere to soften the light, the sun acts as a very sharp single light source, so shadows have very defined edges.

  36. Chip

    I know these great images are in false color – but are they partially in false color? The reason I ask is that it looks like Phobos has acquired a coating of reddish Martian dust over many years, which may not be too far off given its low orbit.

  37. Duane

    I loved the description in one of Kim Stanley Robinson’s MARS books of astronauts standing on Phobos’ surface. The moon is so small that each astronaut was standing at a different angle from all the others.

    Is it even possible to stand upright, let alone walk, on a “moon” like Phobos? It seems like a human, used to 1g, would kick up a tremendous amount of dust and gravel just trying to stay balanced in such a weak gravity field. Can’t wait to get there!!

  38. bigjohn

    Those grooves are made by 4-wheelers. Those damn things are everywhere.

  39. TravisM

    The blog entry over at mentioned earlier has a map that shows just where the grooves lie (lay?)
    It lines up nicely with them having been made by “running over” impact ejecta from mars impact events, not from the Stickney itself. (Bad BA… ;) Is that a double negative?)
    These grooves are entirely concentrated radially from Stickney, but on it’s west side in particular they are tangential to it. Not what you’d expect from the crater being the origin.
    Furthermore, the trailing and leading hemisphere’s of the moon show exactly what you’d expect for this to be due to debri smacking into the windshield, so to speak. The leading hemisphere shows the most scattered chains, the trailing hemisphere is nearly devoid of any such chains!
    Sews it up nicely, I might add.

    Also, if you shoot the ceiling above the chainsaw box, you’ll get a blue health sphere and berserker pack!

    And, in closing: I gotta a bad feeling about this…

  40. Twodogs

    I heard recently that the two moons that orbit Mars are missing and that their is an extencive dust storm on Mars that is lasting longer than usual.


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