More Mars caves found!

By Phil Plait | September 21, 2007 12:41 pm

Well, now we have some better martian news: Mars Odyssey appears to have found many new cave openings on the surface of Mars!

The possible cavern entrances (called skylights) were found by looking for warm spots on the surface during the martian night. The surface of the planet cools rapidly after sunset, but caves don’t have rapid temperature variations. By using a thermal (infrared) imager, scientists were able to spot the cave entrances. They then looked at daytime images taken in visible light to spot the shadowed openings.

The image above shows six of the potential cavern openings. They are all located on the north slope of the volcano Arsia Mons; you’d expect caverns in such a location. The first such skylight was found a few months ago by the Mars Reconnaissance Orbiter.

Something funny– see how those other round features in the images look like domes? They’re actually craters! This is an old illusion (I’ve talked about it before) where the direction of illumination can fool your brain. Don’t believe me? Well, take a look at the image again. See the arrows? One is the direction of north, and the other shows you the direction of the illumination: in all the images, the Sun is on the left. Look what happens when I rotate the image so that the Sunlight is coming from the top:

Amazing, isn’t it? They really are craters! This shows a very important point: you cannot always trust your eyes. You have to understand how the brain works too before interpreting images. Otherwise you might make a mistake, and the data are always prepared to fool you.


Comments (38)

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  1. A Ler…-- Rastos de Luz | September 21, 2007
  1. bigjohn

    Maybe we should rename Mars to Dune.

  2. zeb

    Ahhh! Giant snakes on Mars! Ahhh!

  3. ABR


    In other news, Science Friday on NPR discussed the recent water/no water on Mars issue this afternoon.

  4. Irishman

    Actually, even after rotation they still look domed to me. I can eventually force them to craters, but not just because they’re rotated.

  5. Carey

    Uhh, they look like craters in the first picture, and like domes in the rotated picture. So the data must have fooled me twice! And as our esteemed president says, “Fool me once, shame on… shame on you… you fool me, can’t get fooled again!”

  6. opsmgr

    Nope, still looks like domes to me. O.o

    It’s really amazing how round the holes are. You’d expect them to be more jagged-edged.

  7. Ed Myers

    Further proof that Dr. Plait is one of “them!” Those are actually old city domes! When the water disappeared the Martians dug the tunnels to survive! Then they carved a big face as a distress message! Then “the Military” bombed the face to cover up the existence of Martians!

    Hoagland was right all along and Dr. Plait is just a Bush stooge! The “facts” fit the theory perfectly, so it must be completely correct!

  8. tacitus

    Is there any chance we might eventually want to make use of one of these Martian caves as the site of a human settlement? IIRC, one of the problems of a long stay on Mars is increased exposure to cosmic rays. Finding a suitable cave, say the entrance to a network of lava tubes that we know exist on Mars, could provide excellent shielding at a much lower cost and effort than would otherwise be possible.

  9. Remek

    The amount of ancient caverns/lava tubes and their sizes could well be used for future Mars habitation settlements. The only problems are in sealing the natural opening diameters, and the ‘altitude’ above Mars’ average “sea level” height.

  10. Marlayna

    @The Bad Astronomer: I think you meant to rotate the picture 90 degrees to the *left* ūüėČ

  11. Tukla in Iowa

    But have they found a Martian Daryl Hannah living in any of the caves?

  12. ACW

    Notice the plume of lighter material stretching north from Aperture F. Are there any theories about what that is?

  13. The dome/crater illusion reminds me of the classic Necker cube:

    The rotation of the above photos didn’t force me to see craters either, but what did was the BA’s suggestion. I would have probably continued to see them as domes had I not been alerted and made the effort to see them as craters.

  14. Walter Brameld IV

    Both those pictures look like domes to me. I had to rotate the original image 180 degrees so that the sunlight in the image was coming from the same direction as the lamp on my desk before my visual cortex would admit that those are craters.

  15. Nope, they look more like domes in the rotated image than in the original.

    ACW – I saw that too. I have no clue what it is, but it looks interesting. To my sleepy eyes, in the original picture it looks like elongated, wavy flames. Or a wavery impression of someone giving us the finger.

  16. KaiYeves
  17. There is a little masochistic voice in the back of my mind that wants me to go over to Enterprise Mission to see what amazing cliams Hoagland is making in regards to these caves, but I think I’m going to have to fight it.

  18. Hoagland was right all along and Dr. Plait is just a Bush stooge! The √Ę‚ā¨Ňďfacts√Ę‚ā¨¬Ě fit the theory perfectly, so it must be completely correct!

    [DEITY] I love the Interwebs.

    all those pipes


  19. CR

    I, too, saw craters in the first pic, then domes in the rotated pic. Strangely (or perhaps awesomely), I rarley have trouble seeing craters as craters when looking at pics of them… I guess it comes with having viewed so many of them in my spare time, and knowing what they are ‘supposed’ to be.
    On the other hand, the cautionary advice is still sound: examine all the data, don’t necessarily just trust a first glance.

    Cool pics, by the way, and cool way of locating the caves via their heat signatures.

  20. Thanny

    I frequently get the dome illusion when looking at pictures like that. It doesn’t matter which way the picture is rotated. I think the most important factor, beyond the inability to move and get a different perspective, is that the pictures are face on. I don’t believe our brains expect sunlight from any particular direction, and there are no good cues in the image to go on (such as a horizon).

  21. Lyle Gaulding

    Obviously that’s whee the Martians are. As forsccn by much old SF

  22. Tom

    Very cool discovery, but this is old news. Alan Boyle reported on it (with the same picture) in March.

    Is NASA losing track of their press releases?

  23. BlockStacker

    Mars Caves?! We could live in them! (If it turned out doing that conferred some advantage…)

  24. BlockStacker

    Epoxy the walls to make them airtight so that we don’t have build our own structures?

  25. Craters always look like bumps to me regardless of how I turn the pictures – maybe my eyeballs curve inwards or something…

  26. KaiYeves

    “Enterprise Mission to see what amazing cliams Hoagland is making in regards to these caves, but I think I√Ę‚ā¨‚ĄĘm going to have to fight it.”
    I often feel the urge to find RCH’s E-Mail address and send him the poem “We Wear the Mask”. I think it describes him perfectly.

  27. Are these “skylights” caused by meteors punching through a thin crust and exposing the cavern beneath? Is that why they are so uniformly round? But, if so, then why do the bigger impressions nearby not break through to the underground cavern?

  28. boggis the cat

    So if we do end up populating Mars we’ll be back to living in caves?

    They aren’t lying about history repeating itself, then. :)

  29. Tom

    Odds are, the caves are tubes, not vast open volumes under the ground. The orientation of the tube would be hard to discern in the picture, but I’m betting it would be in the ‘down’ direction of the mountain. The one double skylight in ‘E’ probably shows the direction of a tube, or it’s two tubes side by side. I hadn’t thought about meteors punching the holes, but it’s a mechanism that makes sense.

  30. Cheez Mastah

    I actually saw craters in the pictures until Phil mentioned the domes. Even then, I had to TRY and see domes, which I eventually did.

  31. Science Teacher

    Oh dear. I had to look at the photos again to see the domes.

    Sorry ’bout that. :)

  32. Meags

    In reply to Thanny’s comment: In my job I spend a lot of time looking at large scale aerial photos, and if I have north pointed down instead of up, I often see hills as valleys and vice versa. It can be a bit disorientating, but is instantly fixed as soon as I turn the photos the correct way up. This is irrespective of the time of day the photo was taken.

  33. Tracy

    Who knew that mars would be populated by cavemen? Bet they saved a lot on their car insurance.

  34. AndreH

    Domes / craters

    What helps me a lot is to know the direction were the ligth is coming from. then I “see” the source of light before my “inner eye” and immediately recognise what the shape is.

    It is even possible to flip from domes to craters and vice versa by “putting” the source of light to the other side.

    Great pics!!


  35. ipgrunt

    # ACW on 21 Sep 2007 at 2:32 pm wrote:
    # Notice the plume of lighter material stretching north from Aperture F. # Are there any theories about what that is?

    I share ACW’s curiosity about the light colored area north of the ‘hole’–is this perhaps some sort of wind effect we’re seeing? Could this be a clue to the nature of these phenomena?

    There seems to be similar markings on some of the other photographs, for instance, the photograph marked F on this page:

    has a very long light colored section at the top of the hole.

    In the high-res photo of Jeanne, also available from this page, at 400% magnification I’m seeing what looks to be cliffs and small shoreline-like features in the area of 11 to 12 O’clock, and the object appears to be a round pool of dark liquid, almost a Crater Lake-like caldera feature.

  36. Steven

    If anyone has done their studying; this may draw some interesting theories.
    If you read about the annunaki and etc., earlier civilization documentations, UFO’s and etc., fallen angels, cross-breeds. Aliens. Aliens may also be fallen angels who were casted away. Who’s to say they didn’t traverse space. They may have mutated; or change through physical damage from something or someone(s) or alterings; due to space travel. The caves on Mars could merely be where these beings drilled for precious minerals to bring back to their planet. Who’s to say they didn’t leave something behind.
    These caves could be proof for extraterrestrial existence. Their are too many UFO cases reported over the world. Too much evidence from early civilization documentation and evidence in space. Supports the theory of a tenth planet that comes in and out our solar system. The Broken Bracelet being the planet Tiamat at one time, cataklysmic damage shown on planets as scars, and etc. shows proof of a planet coming in and out. I could keep on going. I’ll stop here.

  37. ???

    if they are holes, wouldnt the way the light hit them be the opposite of how it hits the nearby dunes? i would expect the leading side of a dune in relation to the sun would be lit while the back is in shadow, which you see here. i would further expect that a pit viewed at the same orientation would have the back of its inner area lit, while the front of the visible interior would be cast in shadow by the leading edge of the overhanging crust, but that is not what i see in these photos.


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