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Phobos and/or Deimos from Mars

  1. Mar 29, 2009 #1
    Hi.
    I've been searching the internet for images that the Mars rovers may have taken of either Phobos or Deimos from the surface of Mars, preferable in the daylight. I'm just curious to see that. I would think that the astronomers would have tried to capture such a sight.

    All I've found are time-lapsed images of those bodies passing "in front" of the sun.

    Any information or links would be appreciated. Thanks!
    -Chris H.
     
  2. jcsd
  3. Mar 29, 2009 #2

    DaveC426913

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    Phobos and Deimos are itty-bitty moons (less than 20mi in diameter). They will look like nothing more than stars in Mars' sky.
     
    Last edited: Mar 29, 2009
  4. Mar 29, 2009 #3
  5. Mar 29, 2009 #4
  6. Mar 30, 2009 #5
    Thanks for the reply. Good to know!
    -Chris H.
     
  7. Mar 30, 2009 #6
    I need to hit refresh more often. I was thanking Dave C. But thanks "Touch" for the links. The consensus seems to be that there is no "naked" eye phenomenon with the Mars moons, as we (are fortunate to) have here on earth.

    So, you can tell I'm not a scientist, but I guess I wondered if even though Phobos and Deimos were small, they might be close enough to see. I guess not! :)

    I do appreciate the replies & links. This is very good information for me, nonetheless.
    -Chris H.
     
  8. Mar 30, 2009 #7

    Ich

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    No, Phobos has an angular diameter of up to 0,2°, as seen from Mars. Our moon -seen from earth- is merely 2.5 times bigger (0.5°) in one dimension. Phobos should be easily visible for LGM.
     
  9. Mar 30, 2009 #8

    DaveC426913

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    Yes but visible from the surface as little more than a point. Especially since I doubt any of the landing craft have telescopic equipment. It's likely more wide-angle.
     
  10. Mar 30, 2009 #9
    Glad to hear additional comments, Ich & Dave.

    So, Phobos would basically appear as a grain of rice held at arm's length? And that's if the atmosphere didn't obscure it too much, I suppose?

    Good point about the camera equipment, too. I'm sure that those robots are using wide angle lenses to get all the geographic features.

    I guess I'm just curious: can one stand on the Martian surface and see Phobos with the naked eye during the day?
     
  11. Mar 30, 2009 #10

    DaveC426913

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    Well, it's albedo is ~.06 which is somewhere between fresh ashphalt and charcoal so it wouldn't exactly shine like Venus.

    OTOH, it makes an orbit three times a day, so it would almost move visibly (at least if you saw it against a background of stars).

    I would guess it would be visible at dawn and dusk as a very dim star-like point. But I'm just guessing.
     
  12. Mar 30, 2009 #11

    Ich

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    Phobos' magnitude (from the German Wikipedia) is given as ~-8, which should be pretty bright at dawn.
    I don't think that the rover's angular resolution is a problem, the transit pictures show otherwise. Maybe they need a brighter source and/or the possibility to track phobos during exposure.
     
  13. Mar 30, 2009 #12

    Janus

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    For a visual reference, here's how Phobos woud appear in size as seen from the surface of Mars, compared to a full Moon as seen from Earth.

    http://home.earthlink.net/~parvey/sitebuildercontent/sitebuilderpictures/phobos_moon.jpg [Broken]
     
    Last edited by a moderator: May 4, 2017
  14. Mar 30, 2009 #13

    DaveC426913

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    Really? That's significant!
     
    Last edited by a moderator: May 4, 2017
  15. Mar 30, 2009 #14

    Janus

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    During "full moon" Phobos has a visual magnitude of about -9. Venus, at its brightest, has a magnitude of about 1/2 of that. Since Venus, at its brightest, can be seen during daylight hours on the Earth Phobos should be visible, at times, during Martian daylight even though it won't be full at those times.
     
  16. Mar 30, 2009 #15

    russ_watters

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    I didn't realize until seeing this thread and googling: Phobos orbits Mars at ~9,400 km from the center of Mars, whereas our moon's is 384,000 km. So Phobos looks so big because it is so close.
     
  17. Mar 31, 2009 #16
    Hi all.
    Clearly, we've identified an item for the next Mars mission wish list.

    I first thought about this when I was thinking about whether the Martian atmosphere was too "hazy" to see very good starscapes, etc. and how crazy that would be from its high altitudes to see many, many stars against a very curved horizon (due to its much smaller diameter than Earth).

    Than I saw "Watchmen" which depicted some activities on Mars, and they showed a moon (it was Phobos) in the sky. I was then curious if you could actually see it that well, and if you could see it in the daytime.

    Anyway, it's all very fascinating. Mars seems to be even cooler now than it did in the 70s!
     
  18. Mar 31, 2009 #17

    mgb_phys

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    Magnitude is the total flux of course - so Phobos might not be all that visible if it is the brightness of Venus spread over 1/5 of the area of the moon
     
  19. Jun 21, 2010 #18
    Here is an image I found online. I'm not sure what it is. It doesn't appear in the forum I found it on though. It appears to be the mars rover taking pictures of both demos and phobos on various times they are both in the same part of the sky. Then later someone came put them in together to make it look like a continuous video. But if that's the case you'd expect there to be more of these.

    [PLAIN]http://www.muk.uni-hannover.de/~theusner/mars/2P_SOL585_Phobos_Deimos.gif [Broken]
    Here is the forum that google brought up with it even though i didn't see it on the page. There are other pics that are interesting. It's about astronomy from mars
    http://www.space.com/common/forums/viewtopic.php?f=12&t=4673&start=80
     
    Last edited by a moderator: May 4, 2017
  20. Jun 23, 2010 #19

    Vanadium 50

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  21. Jun 23, 2010 #20

    DaveC426913

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    :confused:

    If it isn't where it is, where is it?
     
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