Unpeeling the history of water on Mars

By Phil Plait | February 22, 2010 8:04 am

Years ago, I visited the Grand Canyon with my family. The beauty of it was overwhelming, and everything they say about it is true. It’s magnificent.

That grandeur is only amplified by the obvious scientific significance of it. The layers of sedimentary rock, exposed by the eons-long patient erosion of the Colorado river, are a dramatic open textbook of the geological history of our planet, as if the Earth itself is saying "Look here, and learn of the past!"

Learn we have. And the Earth, as we have also learned, is not entirely unique. From millions of kilometers away, another canyon beckons us to uncover a planet’s past.

hirise_gale_oblique

[Click to engrandcanyonate.]

What you’re seeing here is a topographical model of a small part of a crater floor on Mars: Gale Crater, to be precise, a monster 150 km (90 miles) wide impact located nearly on the equator of Mars. In its center rises a mountain, a central peak common in large impact craters. Surrounding this central peak is an enormous mound of material, rising kilometers above the crater’s floor (see the topographic image below; the ellipse represents an old potential landing site of the Spirit rover). It’s not entirely clear how this mound formed; however, it’s likely that the entire crater was once filled with material laid down as periodic deposits, and that most of it has eroded away, leaving just that lopsided mound.

gale_crater_topoIf that sounds familiar, it may be because the Grand Canyon has a similar history (without the crater, of course).

And like its terrestrial counterpart, the exposed layers tell a history of Mars’s geologic past. Scientists studying those layers using images from the HiRISE camera on the Mars Reconnaissance Orbiter have uncovered a startling feature: while sulfates (deposited by salty water) are seen throughout the layers, clays are only seen lower down, deeper into the past. Clays are only seen where water is abundant, but sulfates alone indicate conditions where water evaporated away.

What the floor of Gale Crater appears to be telling us is that standing water, at least locally, existed long ago on Mars, but later evaporated away. This is consistent with what we have seen in other parts of Mars, of course. Ever since the rovers landed on Mars we’ve seen one piece of evidence after another of standing water in the Red Planet’s distant past.

But there’s something about this news that appeals to me, that touches more than the scientist part of my brain. If I hadn’t told you that first image was from Mars, you might very well think that it was from the Grand Canyon or some other Earthly feature. And it really is a canyon, as you can see from this HiRISE image of the same area:

hirise_gale_crater

This image shows the very lower left of the oblique view shown above. It’s upside-down, making features difficult to compare (check out the full HiRISE image of the area to see the whole thing), but the crater floor is at the top of this false-color image, and the mound begins to rise toward the bottom. You can see the canyon carved right into the floor, with sand dunes rippling across it.

Whatever carved this canyon, perhaps hundreds of millions of years ago, perhaps more, tore away the deposited material and revealed all those layers of rock. These layers can be read like a history book written in reverse chronological order, showing us the deep past of Mars, and telling the sad tale of how an entire planet lost its water.

Mars was once more like the Earth is now, though just how much is anyone’s guess at the moment. I doubt it was exactly like Earth; the evidence of water we see indicates it was incredibly salty, far saltier than we have here at home. But still, Mars is a brilliant ochre cautionary tale in our sky. There but for the grace of water go we…

Comments (23)

  1. feroxx

    “engrandcanyonate” :D

    Awesome pictures, thanks!

    …oh, the link to the picture is broken here?
    did you mean this?
    http://www.nasa.gov/images/content/424745main_pia12507-full.jpg

  2. bigjohn756

    Gosh, this means that there was a Flood there, too. That pretty much confirms life on Mars at one time, doesn’t it? Otherwise, Almighty God would have no reason to flood the place.

  3. Pictures like this are amazing. Who would have ever thought we could know so much about mars? I too am very interested in how those canyons were carved.

    Wait! Maybe it was by the same people who built the pyramids on Earth! (Darn gremlins.) :)

  4. But does this yield any information on whether or not the water does in fact contain sentient viruses intent on piggybacking to Earth? These are questions that must be answered before we risk a manned mission!

  5. Peptron

    <creationist mode>
    Just as you’d think creationists were losing support by scientists about the biblical flood theory of the Grand Canyon formation.

    Here is what Phil Plait had to say about the creationists supporting global flood geology:
    “Years ago, I visited the Grand Canyon with my family. The beauty of it was overwhelming, and everything they say about it is true.” -Phil Plait
    </creationist mode>

    (I consider that my attempt at quote mining deserves bonus points, since the paragraph directly after what I quoted completely contradicts it and proves that I am full of it. But I am not full of it, I am merely persecuted. And you all know how I like being persecuted *wink* *wink* *nudge* *nudge*.)

  6. DaveS

    I think it’s totally wasteful of resources to mount manned expeditions to the Grand Canyon. I think we should focus our limited budget on scientific robotic expeditions, and just look at the pretty pictures that produces. If private industry wants to visit it in person, fine.

  7. Just remember, if you ever do find water on Mars, don’t let it touch you. NOT. ONE. DROP.

  8. Doug

    “…everything they say about it is true”

    You might want to specify the antecedent to your pronoun there! :)

    http://creationwiki.org/Grand_Canyon

  9. Jim

    If the world was created 5,000 years ago, would a YEC say that there must have been a flood on Mars too?

  10. I don’t know about *a* flood on Mars, but *The* Flood were on Mars.

    Ok, last “The Waters of Mars” comment, I promise.

  11. 24601

    “As you are now, so once was I,
    As I am now you soon may be…” ?

  12. Messier Tidy Upper

    What you’re seeing here is a topographical model of a small part of a crater floor on Mars: Gale Crater, to be precise, a monster 150 km (90 miles) wide impact located nearly on the equator of Mars.

    Named after the West Indian batsman and cricket cpatain Chris Gayle, I presume? ;-)

    See : http://en.wikipedia.org/wiki/Chris_Gayle

    I doubt it was exactly like Earth; the evidence of water we see indicates it was incredibly salty, far saltier than we have here at home.

    Well, we do have some incredibly salty waters on Earth too – the Dead Sea in Israel and, when they have water in them, South Australia’s Lake Eyre, the USA’s Bonneville (spelling?) salt flats, Utah’s Great Salt lake, Lake Mono (I think) and so on. How do they compare with the saltiness of Mars?

    Actually, even in the south east corner of my home state of South Australia there’s a small lake of highly salty water called the Pool of Siloam which I’ve personally swum in myself!

    Mind you, I’m guessing the chemical concentrations and constituents would be quite different Earthly versus Martian, right?

    But still, Mars is a brilliant ochre cautionary tale in our sky. There but for the grace of water go we…

    Actually, isn’t it more the “grace of *mass*” because if Mars was more massive it would have retained its atmosphere, likely have plate tectonics and still hold its water?

    If Mars was the mass of Earth or even a bit less – if Mars and Venus had switched places I ‘d suggest it could still be a habitable living planet today.

  13. llewelly

    USA’s Bonneville (spelling?) salt flats, Utah’s Great Salt lake

    Water on the Bonneville salt flats is seasonal; they are usually bone dry in August. Beautiful place to visit (seen a few drag races and a few model rocket launches there), but do not forget your sunblock.
    It could be argued the Great Salt Lake is the non-seasonal part of the Bonneville Salt Flats.

  14. Gary Ansorge

    Phil:

    “telling the sad tale of how an entire planet lost its water.”

    I’d suggest it would be more accurate to state that an “entire planet lost its’ water” w/o referring to the “how”. I saw little in your post that would posit the “how” of water loss. THAT might take another, longer post.(granted, you were probably referring to the historical “how” rather than the mechanism of water loss, but still,,,)

    Now, if we could just figure out how to move Venus to the orbit of MArs,,,

    Great pics.

    GAry 7

  15. Messier Tidy Upper

    @ 13. llewelly Says:

    “USA’s Bonneville (spelling?) salt flats, Utah’s Great Salt lake”

    Water on the Bonneville salt flats is seasonal; they are usually bone dry in August. Beautiful place to visit (seen a few drag races and a few model rocket launches there), but do not forget your sunblock. It could be argued the Great Salt Lake is the non-seasonal part of the Bonneville Salt Flats.

    Okay thanks – I didn’t know that last bit there. :-)

    I *did* know about the seasonal or often dry nature of Bonneville Salt Flats though – that’s why I prefaced it and Australia’s Lake Eyre with ” … and, when they have water in them…” in my comment originally. (#12) ;-)

    Anyone know how the saltiest waters on Earth compare with the salty waters of Mars? Equally salty? Saltier? Less salty?

    (& where can you get fish & chips on Mars to add that salt too? ;-) )

  16. Jon Hanford

    Came across this on arXiv today and couldn’t resist. Any comments Phil?

    “Bacterial survival in Martian conditions” at: http://arxiv.org/abs/1002.4077v1

    Made my day! :)

  17. Jon Hanford

    Still stuck in ‘moderator limbo’! Try cut & paste this link: (http:) //arxiv.org/abs/1002.4077v1 to read “Bacterial survival in Martian conditions” (I kid not) from today’s arXiv. :)

  18. Grand Lunar

    Pretty cool stuff!
    Shows what good science can do.

    You’ve seen the Grand Canyon, Phil, but have you hiked in it yet?
    One time when I did so, I noticed some areas on the walls that looked as red as Martian soil.

  19. Roen

    peel = To strip or cut away the skin, rind, or bark from; pare.
    Therefore to “unpeel” is to put it all back on.

  20. Markle

    @M_T_U Don Juan Pond is about as salty as it gets. It’s so salty that it doesn’t freeze in winter even when the temp reaches -30C. It’s less than a foot deep. Still supports life. Lake Vanda nearby, is about 2/3 as salty and more lake-like in depth and extent. Outside Antarctica’s dry valleys, there’s a crater lake in Africa and then the Dead Sea.

    It’s Mono Lake, BTW.

  21. Pi-needles

    @ ^ Markle : Thanks. :-)

    - aka Messier Tidy Upper

  22. James Mayeau

    More interesting then the question of how the water on Mars was evaporated away is the realization that there was a point when water flowed as a liquid on the surface next to a geological record which allow correlation with historic climate periods on Earth.

    In the previous thread Phil Says:
    February 21st, 2010 at 12:03 pm
    Jason (55): The Sun is not the cause of global warming on other planets. If Mars were warming a little, the Earth would warm a LOT. Read this.

    That statement is in conflict with the facts.

    Care to revise your statement sir?

  23. den

    Mars lost its water when the “Fifth Planet” exploded
    to create the asteroids. This is evidenced by
    the one side of Mars which is heavily cratered.
    Any intelligent astrophysicist could figure this out.
    den
    *****

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