Phobos passes Jupiter… as seen from Mars!

By Phil Plait | June 17, 2011 12:40 pm

Mars Express is a European Space Agency probe that’s been orbiting the Red Planet since 2003, returning vast amount of data. Lately it’s been taking some amazing images and video of the tiny Martian moon Phobos, and the ESA just released this amazing footage of the lumpy potato moon passing by Jupiter as seen from the orbiting craft:

How cool is that? Engineers saw this viewing opportunity and actually changed the orbit of Mars Express to be able to see it. Phobos passed a mere 11,400 km (6800 miles) away when these shots were taken, but Jupiter was 530 million km (320 million miles) in the background. That’s why a moon only 27 km (16 miles) across can appear to dwarf a planet 140,000 km (86,000 miles) across! In the diagram here, the relative positions of all four players is shown; click to enbarsoomenate.

The animation consists of 104 frames taken over a period of just over one minute. It’s useful, too. By knowing the position of the spacecraft and Jupiter, the orbit of Phobos itself can be better determined. Phobos is weird: it orbits so close to Mars that tidal drag is actually lowering its orbit. In roughly 10 million years the moon’s orbit will have dropped so much it will impact the planet!

One other thing: my love for red/green 3D anaglyphs is on record. So I was delighted to see the ESA also put this terrific one up:

I know, it’s just a gee-whiz thing, but I can be a kid too sometimes. That’s simply cool!

Credits: ESA/DLR/FU (G. Neukum) & USA Today

Related posts:

Phobos is, like, totally groovy
It’s rabbit^h^h^h Phobos season!
More *incredible* Phobos imagery
The shadow of a moon goes passing by


Comments (22)

  1. Carey

    I wish videographers and photographers would also create stereo images when they create red/green and red/blue anaglyphs, for those of us who prefer our 3D in the correct color and sans glasses.

  2. jay

    ‘Lumpy Potato Moon’ is now the name of my next band.

  3. Rich

    I’m with Carey. Give us stereo pairs! I had to learn how to view them in college without glasses and darn it I want to put all that money I spent go to good use!

  4. bouch

    Wow. Wicked cool. I’m amazed at how well you can see the Jovian cloud layer. I know Mars is a lot closer than Earth, and I’m sure the picture was taken through a a pretty good telescope on that satellite, but when Jupiter is a dot to us on earth, I didn’t expect it to appear that much bigger.

  5. Moss

    I wonder if/when Phobos impacts Mars if it would send a dangerous spray of debris in Earth’s direction?

  6. cy

    My thoughts are the same as bouch? What kind of magnification is needed to see Jupiter that well? Mars is closer, but not that much closer.

  7. Unaspammer


    Actually, I’m a bit disappointed that the video looks like a bad Flash animation, although I don’t know why I should be expecting anything else over such a small viewing angle.

  8. Matt L

    NASA and the ESA and such should get together with Nintendo to create 3D images I could see on my 3DS screen. I have a really hard time going back to the red/green anaglyph stuff. And it just makes so much sense! Imagine how many people’s imaginations would be stirred by high quality 3D images on their handheld? They could tap into an audience that might otherwise not even know about this stuff.

  9. I sincerely hope that the “regular” 2D images will never go out of style. Since I only have one good eye and can’t see 3D.

  10. Keith Bowden

    FYI: I clicked through to the ESA’s page to watch it, but all I see here is a big blank white space where (presumably) the animation should be.

  11. DrFlimmer

    Sometimes I get the impression that Mars Express is almost forgotten, with all the American counterparts at and on Mars.
    Good to see that ME makes some good stories as well from time to time!

  12. I have no idea why but I thought that was hilarious. Phobos looks like some kind of dopey headed thing and the way it was set up just made it look silly.

  13. Grand Lunar

    “I know, it’s just a gee-whiz thing, but I can be a kid too sometimes”

    You and me both, Phil!

  14. Messier Tidy Upper

    Great clip. Thanks. :-)

    @13. Grand Lunar : Me too! Thirding that. 😉

    @12. Endyo :

    I have no idea why but I thought that was hilarious. Phobos looks like some kind of dopey headed thing and the way it was set up just made it look silly.

    Well, as (#7.) Unaspammer has noted it does look a bit like an animation – even though we know it’s real. Hilarius? Not to me but curious and a bit quirky perhaps. 8)

    @5. Moss :

    I wonder if/when Phobos impacts Mars if it would send a dangerous spray of debris in Earth’s direction?

    Exceptionally unlikely! Given the distances apart that Earth and Mars are and the amount of space in, well, space I really don’t think so.

    Most of the debris will probably crash back onto the martian surface – some of it could be ejected into martian orbit and the area near the planet, with, (I’d expect) some of that material later being gathered up by the red planet again on subsequent orbits. I suppose it is possible that some tiny percentage of the debris will eventually reach the Earth but if it does it is unlikely to be for a very long time afterwards and unlikely to do much serious damage.

    Phobos is a very tiny moon – so small it’s been noted that :

    “If we could transport Phobos and Diemos to our own Moon, they would fit comfortably inside the wide crater Copernicus with room enough for two moons of similar size.”
    – Stephen James O’Meara, page 102 “The Demon Sprites of Mars” in ‘Sky & Telescope’ magazine, June 2001.

    Thus we’re talking about a very tiny percentage of a very tiny moon which is NOT going to make a major impact. Even adding in a fraction of possibly ejected Mars rock this is still, I think pretty much the case. I may be mistaken tho’ natch.

  15. JohnDoe

    Carey and Rich, turning this Red/Cyan anaglyph into Stereo Pairs is trivial, since the original is just greyscale. Just separate the R,G and B channels, the G and B should be identical in this case so you can drop one. The remaining channels are your stereo pair. Alternatively, you can just set either R or G and B intensity to zero and save the result as a greyscale image, as I did here:

    While I do have a pair of cyan/red glasses on my desk just for those images, I have trouble seeing any 3D effect at all in this case.

  16. Lars Bruchmann

    Das Video ist absolut super! Es sieht zwar mehr wie mehrere Bilder aus anstatt ein glattes Video aber das man rechnen konnte wohin man die Sonde lenken muss um den Mond und Jupiter im Bild zu haben ist doch eigentlich unglaubbar!

  17. Harmen

    I’m amazed at the relatively big apparent size of Jupiter at the distance of 530 million km (320 million miles), and the fact that we can see the cloud bands in its atmosphere! There must be quite some magnification involved.

  18. James

    I agree with Harmen, being able to see such detail on Jupiter in that shot is outstanding. That was the first thing that grabbed me in that picture.

  19. Regner Trampedach

    Thanks, Phil, for yet another post with stirring pictures. And an applause to ESA and the Mars Express team!
    Nitpick: It is just “ESA” not “the ESA” – just like it isn’t “the NASA”, “the JAXA” etc.
    Cheers, Regner


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