Pits indicating a Martian underground river?

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A string of pits suggesting a past underground river system on Mars
Click for full image.

Cool image time! As my regular readers well know, I am a caver, and am thus always interested when the high resolution camera on Mars Reconnaissance Orbiter (MRO) takes a close-up of a pit that might also be an entrance to a cave.

The photo to the right, cropped and reduced to post here, was part of the most recent image release from MRO, but was boringly labeled “Arabia Terra” after the region where it is located, one of the largest transition zones on Mars between the northern lowland plains and the southern cratered highlands. When I took a close look, what I found was an intriguing string of pits whose arrangement is strikingly reminiscent of a river tributary system.

The white box indicates one section that I have zoomed into, as shown below.

Close-up of pits

Gosh, that sure looks like there was an underground drainage, flowing from the right to the left, with two tributaries coming to a confluence that on the wider image above continues to the north and west until it combines with another set of tributaries and then heads west. Whatever had flowed underground had eventually eroded a large enough passage for the ceiling to collapse in multiple places along its length.

Of course, we have no idea if these pits are skylights into a volcanic lava tube, or a former water passage. The low latitude, only 5 degrees north of the equator, argues against liquid water, but then, this is also the same latitude as the giant canyon Valles Marineris, which scientists think might have been formed by catastrophic floods.


The overview map on the right provides this context. The red cross indicates the location of this image. The blue cross indicates the area the rover Opportunity explored.

The implied direction of the underground drainage, to the west, also makes sense. The general downward grade for Arabia Terra is to the west and north.

Finally, the color strip in the top photo provides one more intriguing detail. The ground surrounding one string of pits is differently colored than the surrounding terrain, suggesting a different make-up. To my eye this looks like dust material that might have been blown from the pits, but that’s a pure guess.

Is there a cave system here? We do not know, though other research supports this hypothesis.



  • sippin_bourbon

    Nah….whatcha got there is a gopher problem…

  • Tom Billings

    I think this article by Leonard David may give even more info about martian lava tubes newly found, …or rather, “candidates” for lava tubes:


  • D3F1ANT

    What can one even believe about Mars? Whenever there’s a hiccup at NASA we find that they’ve been pulling yet ANOTHER gambit to recolor the images, or blur out the details, or otherwise misrepresent/camouflage what’s happening on Mars. And I’m not even one of the guys who swears there are aliens or cities there! Who knows why the government plays the games it plays? But it’s sad you can’t even trust them to share a snapshot.

  • Whisperin Pints


    Brilliant observation. Some folks are thoroughly rapt with the idea that in the Martian past there was a much different atmosphere and biosphere with abundant water. I suspect their flights of fancy are based on Earth’s history, which is understandable. Earth’s history also included megaflora and megafauna. Thus, positing the existence of mega-gophers in Mars’ past is NOT unreasonable.

  • Doc

    Hmmm…that could be a nice system that could provide habitat for long term colonization. Underground passages could be sealed, providing pressurized comfort, as well as protection from solar elements and meteorites. The penetrations could be sealed off with lexan to provide sunlight for plant production for food and oxygen. That would save a trillion dollars in transport costs for more conventional structures.

  • Bubba

    Mars cannot exist since the earth is flat. In order to have “gravity” the earth is continuously accelerating at 1G. If there was a mars it would have to be accelerating in the same direction as the earth in order for us to be close enough to fly to it. Plus mars is smaller than the earth and 1G acceleration of mars would be a different speed so it would not be anywhere near earth after 5 billion years. NASA is making this stuff up and it’s obvious to all.

  • wayne

    A message from Penn & Teller, just for you–


  • wayne: I really don’t consider this funny. It is the equivalent of cursing at someone, by having a proxy do it.

    As you didn’t directly break my rules, I think it would be unfair to suspend you. However. please don’t link to such videos again, or I will ban you.

  • wayne

    Ok, I understand. I shall endeavor to comport myself public-wise.

    “Rotation in Space”
    Professor Carolin Crawford
    Gresham College Public Lecture 2012

  • wayne

    Joe Rogan and Michael Shermer
    “Flat Earthers”
    (excerpt of show #847)
    September 2106

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