Liquid water on Mars? Maybe not.

By Phil Plait | March 1, 2008 10:00 am

Well, nuts.

A little over a year ago, NASA announced it had found strong evidence of liquid water flowing, at least temporarily, on the surface of Mars. Pictures taken a few years apart showed flow-like gullies in the sides of craters, and there were a few different pieces of evidence that these were due to sudden flooding of liquid water downhill. Here are the original shots:

However, a new study just released says that these images fit better with being dry grains flowing downhill.

The researchers, led by Jon D. Pelletier of The University of Arizona, used HiRISE, the very high-resolution camera on board the Mars Reconnaissance Orbiter, to look at the same regions as observed before. By taking images at different angles, they could establish a digital elevation model, a topographical map of the same crater shown in the earlier announcement. They then modeled the way liquid water would flow under Martian conditions compared to how dry grains would flow. To their surprise, they found that dry grains were a better match. From their press release:

“The dry granular case was the winner,” said Pelletier, … “I was surprised. I started off thinking we were going to prove it’s liquid water.”

Finding liquid water on the surface of Mars would indicate the best places to look for current life on Mars, said co-author Alfred S. McEwen, a UA professor of planetary sciences.

“What we’d hoped to do was rule out the dry flow model — but that didn’t happen,” said McEwen, the HiRISE principal investigator and director of UA’s Planetary Image Research Laboratory.

An avalanche of dry debris is a much better match for their calculations and also what their computer model predicts, said Pelletier and McEwen.

While this isn’t conclusive, it does seem compelling (they can’t rule out very thick mud, incidentally). The press release doesn’t have any statements from the scientists who made the previous announcement about water, and I’ll be very curious indeed to hear what they have to say.

If it holds up, it’s too bad. I’d love to see better evidence of ubiquitous water on (or immediately under) the surface of Mars. But facing reality is what we have to do. Of course, as our tools get better, we’ll get better at figuring this stuff out, too. It helps that so many people involved are so very clever.

A final note: I reread my original blog post about the announcement of possible water. While I think the content of my post was suitably skeptical, I let my feelings get away from me a bit in the headline: "LIQUID WATER ON MARS!" Hmmmm. Looks like sometimes I need to remember my own advice. :)

CATEGORIZED UNDER: Astronomy, Cool stuff, NASA, Science, Skepticism

Comments (38)

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  1. zeb

    Yep, the cold hard slap of reality is always better than what we might want it to be. I’ve had to come face to face with this many times in my life (I used to believe in a bunch of wierd things like ghosts, UFOs, etc.) and I’m glad I’ve chosen critical thinking and skepticism for my life over woo.

  2. Phil, your acknowledgement of premature excitement is much appreciated. Nevertheless, it’s a shame the way that emotional reactions occur so frequently in this particular realm of scientific inquiry. Hopes and wishes often quash diligent research. NASA knows what the public wants to hear. After the Martian water story was released in 2006, some true believers were trumpeting that they knew it all along while everyone else had been closed minded.

    Much of NASA’s funding from Congress depends on attempting to find life or at least water. Remember when NASA got the president to announce possible microbial fossils in a Martian meteorite? Not long after that, one of the chief NASA engineers on the 1990’s Mars Pathfinder vehicle was a guest on my TV program. When I showed him fresh news off the wires of European scientists with access to the meteorite claiming the nodules were ordinary chemical formations, he was crestfallen.

  3. Guy

    Hi Phil. That’s “HiRISE”. “HiRES” is a soft drink. Thanks for the link though!

  4. chimango

    I think that is a nice example on how science shows things for what they are, rather than what we want them to be.

  5. Guy- d’oh! I know precisely why that happened. I used to work on a computer we named HIRES (we had a LORES too). I sometimes have to stop and force myself to write HiRISE.

    I had a hard time not calling Swift STIS, too. :)

  6. Well, that’s all part of the process. Sometimes you get em right, sometimes you get em wrong. But everytime you learn something. And that’s the real deal.

  7. I think the universe we have will always turn out to be more interesting than the one we think we want. I share Curt Renz’s concern that the fortune of astronomy (particularly planetary exploration) is too closely tied to astrobiology. I think that ultimately it’s a failure to learn the lesson of Copernicus: we are always looking for ways to put ourselves back at the centre of the universe. I applaud the universe for frustrating us.

    This paper adds to our knowledge of Mars and the processes on it: how could that possibly be a cause for disappointment?

  8. Don’t take it too hard, BA. Confirmation bias is a sneaky thing, and it bites us all from time to time.

  9. bkallee

    Your original post was on the mark for what we knew at the time. Easy to forgive a screaming headline. I’ve (partially) trained myself to ignore them. I follow the Mars projects closely.

    One thing that is not explained to my satifaction is how equatorial water, even as rock hard ice can exist in martian conditions near the surface for a couple of billion years, say within 10 meters . Coming from deeper in the crust I understand. Even though I’ve asked the question of a couple geoligists that I know who follow the Mars projects, their possible explanations don’t ring a 100%. Any water would long ago have evaporated, unless it is near the poles, deeper that a few meters and would exist only as vapor.

    They don’t work on any Mars projects though, they work on the Grand Canyon and local ruins.

  10. Chek

    Cool !!!!!!!!!!!!!

    have you seen the latest amazing news on Saturn !!!!!

    Right hand side of page under astronomy news …

    http://astronomy-watch.blogspot.com

  11. madge

    The scientific method wins again! You look to prove a theory and the evidence seems to point in exactly the opposite direction. If you are a Creationist you completely ignore the evidence. Scientists look, look again and then try to figure out what the evidence is telling them. I LOVE SCIENCE!

  12. Brando

    See, here’s a prime difference between Faith and Science. In this case, we really WANTED to find evidence for water on Mars, but thanks to intellectual honesty and the scientific method, we get an answer we’re not exactly too thrilled about but is more likely the truth. Science: it works, bitches! Oh and CFD does too ;)

  13. revmonkeyboy

    I would tend to believe that it is the dry grains, as this has been modeled with more data. The atmosphere of Mars is so very thin, so it is not surprising that this is most likely not water. Mars geology is pretty great and I welcome all the data we can get. The poles are really the best places to look. Lucky we have a lander with a small shovel on its way. I am not sure it will find water either, because what we need is a good drill, IMHO. But I am very curious to see what it does find out about the chemistry and such. I am also excited about the finds of what appear to be caverns or caves. This may be areas that formerly had ice, that has evaporated over time. Mars is very cool, the same laws of physics, different conditions.

  14. Chip

    Critical thinking also means that it would be quite premature to totally rule out any microbial life anywhere on Mars because topographic features thought to be the result of seeping water in a crater are very likely dry dust.

  15. Grand Lunar

    At least we know frozen water is on Mars.

    Maybe somewhere, beneath all that ice, we can find something…

    ‘Course, I’d love to see a similar search take place at Europa.

    Someone must yell to Congress “Hey! We’ve got this great place that has a chance for life! Approve a mission to go there, okay?”

    Then again, maybe they’re afraid of what we’ll find at Europa, or at least the consequences of such a discovery.

  16. blizno

    Chip:
    “Critical thinking also means that it would be quite premature to totally rule out any microbial life anywhere on Mars because topographic features thought to be the result of seeping water in a crater are very likely dry dust.”

    Absolutely. This calculation greatly weakens earlier (water-gushers on Mars!) speculation that was very emotionally appealing. This news in no way shows that there was never life on Mars or that simple Mars-life may not still exist under the best conditions that Mars still offers. It just means that the observations in question probably were not of recently flowing liquid water.

    Brando:
    “…In this case, we really WANTED to find evidence for water on Mars, but thanks to intellectual honesty and the scientific method, we get an answer we’re not exactly too thrilled about but is more likely the truth. …Oh and CFD does too”

    So true. I read blog after blog from conspiracy-sayers shouting that scientists are marching shoulder-to-shoulder fighting against anything that doesn’t agree with their “dogma”. This report is a prime example of scientists heaving a sigh for the loss of a very emotionally appealing possibility and then continuing their pursuit of figuring out the universe with clear eyes.
    I’ve tried to argue on woo-woo sites that many scientists would sell their first-borns for the chance to disprove a well-accepted theory and thereby become centuries-famous and fabulously wealthy. No woo-woo artist has bothered to respond to that argument…

    By the way, what is “CFD”?

  17. blizno

    Grand Lunar:

    “…Then again, maybe they’re afraid of what we’ll find at Europa, or at least the consequences of such a discovery.”

    Such as an abandoned Earth vessel with skeletons in the cryo-pods and two EVA pods waiting for what’s left of HAL to activate them?

  18. It looks like a win for the scientific method.

  19. I agree this is a classic example of how the scientific method works and will be good conversation material in the classroom.

    There is something I’ve been curious about since the initial report – has anyone figured out how liquid water would react under those conditions? I was a little skeptical (though hopeful) about the liquid water report because it seems to me that water would sublimate or freeze almost instantly under these conditions. Has anyone actually tried simulating a large mass of water running down the side of a hill at temperatures and pressures present at these crater locations? I would think this could be done fairly easily with a computer model.

    On the issue of Europa, my understanding is that it isn’t so much a funding issue holding up a Europa mission as it is that we don’t yet know what we want to do or how to go about doing it. Keep in mind that we have drilled to within a few meters of Lake Vostok in Antarctica and have refrained from drilling the rest of the way for fear of contaminating the lake. How would we drill through the ice of Europa, which is over a hundred kilometers thick and harder than steel at those temperatures, without contaminating the ocean below it? This is both an ethical question and a scientific one. We must, on one hand, take into consideration the possibility of permanently changing an alien environment that has an excellent chance, in my opinion, of having life. Also, if we do find life, we need to be totally sure that anything we find didn’t come in on the spacecraft. The power source needed for this task must also be considered. The only power source I can think of that could do this job is nuclear. I don’t have any issues with putting nuclear reactors in space, or even orbit. But, if you start talking about putting one on the surface of the ice or into the under-ice ocean, this is a whole new game and we need to think long and hard about that one. These kinds of issues have to be resolved before we can go to Europa.

  20. “I was surprised. I started off thinking we were going to prove it’s liquid water.”

    I often see scientists making this sort of statement, which is essentially “If I’m right, we should see A, and not B. We found B. I was wrong, and I’m glad to be corrected.”

    When’s the last time a priest or theologian made a similar statement, or was even surprised at their conclusion?

  21. blizno

    The Wiccan Scientist:
    “The only power source I can think of that could do this job is nuclear. I don’t have any issues with putting nuclear reactors in space, or even orbit. But, if you start talking about putting one on the surface of the ice or into the under-ice ocean, this is a whole new game and we need to think long and hard about that one. These kinds of issues have to be resolved before we can go to Europa.”

    I don’t see this as a significant problem. By far the greatest danger with nuclear-powered spacecraft is the possibility of them exploding during launch or re-entry (or entry, in the case of Europa), and spreading hundreds of kilos of highly radioactive matter across territory visited by living things.

    In the case of Europa, the greatest danger will take place outside the thick ice-shell protecting the possible ocean(s). If the craft explodes and sprays ultra-toxic nuclear material across kilometers of frozen surface, any critters living in the liquid far, far beneath the surface will never know it. It’s only once the spacecraft has landed and is in good condition that its probe will begin to melt its way through the thick ice. Travel through the ice and into any liquid under the ice is very, very safe compared to the journey the craft had to endure to even land on the surface.
    My concern is the inadvertent survival of a few Earth-microbes in small crevices in the spacecraft. Hopefully, the heat of the entry shock-wave should sterilize any Earth-critters not human-sterilized before launch that manage to survive the very long journey through the vacuum and solar radiation. It’s barely, just barely, possible that one or more micro-spores could make it that far and then proceed to colonize the under-ice ocean to the possible detriment of Europan life.
    A sub-ice nuclear accident involving the Earth robot…vanishingly unlikely.

  22. Tom Marking

    I’m actually a little bit skeptical of this new report which concludes that the plume of material in the Martian crater was caused by dust grains. It’s pretty obvious from the photo that the plume is lighter in color than the surrounding rock. If it’s composed of dust grains then wouldn’t the dust grains have to originate from some mineral source that was lighter in color than the surroundings? If you look closely at the photo there does not appear to be any rock that’s significantly lighter in color at the top of the plume. If there was a big ol’ lightly colored boulder just above the plume then I would buy this explanation. But there doesn’t appear to be. I still think the fluid deposition explanation is better.

  23. Yay for science although I don’t find this surprising for reasons going back a few years…pull up a chair.
    Many years ago, about 1995, I was on a caving expedition to the Nullarbor Plains in Australia. We were in an area overflown by others in ultralights and interesting surface features had been logged with those new fangled GPSr things. For those who are not aware, this is a very desolate bit of Australia and is a huge flat area with very little rainfall. It is a typical Karst landscape with no rivers or streams and when it does rain the water soon goes underground. It’s really dusty, really old and not a lot grows there.
    In one particular new cave with a promising breeze, which we had to open up the main passage, we found a large cave system, which we proceeded to explore and survey. A long way in from the surface and through many twisty tight passage we came across a low room which had incredibly deep dust. The sort of dust that is so fine it never seems to settle if disturbed and easily gets through seals into camera bodies, watches etc.
    It was bloody horrible to say the least. You could easily push your hand 15cm down into it where it was piled up.It was also totally non-disturbed by any creature for many tens of thousands of years but something did catch my eye.
    Around the edges of the low chamber the dust was quiet steep and there was these little flow marks that looked like tiny rivers down the steep parts of the slopes that were perhaps half a meter high. They started in random places and went for few centimeters. What was interesting was the braiding and little delta shapes where they ended.It looked like grains of rock, sugar-grain size or smaller, had been falling off the roof and walls and causing a mini landslide. The wall and roof rock grain size was much, much larger than the dust.
    At the time I (stupidly) didn’t think much of it nor take a photo (I wasn’t the photo dude) as I was busy with a tape and compass.

    However years later when the first hi-res images came back from Mars showing the potential water caused landforms I remembered that cave on the Nullarbor. Sure the scale was different however it basically looked the same. Someone should do the experiment with a sealed stable box and really, really fine dust, just out of interest.

  24. Douglas Watts

    Tom — the surface material should be darker than that underneath due to chemical weathering and accumulations of dark iron or manganese oxides (ie. desert varnish on Earth deserts). The granular material underneath the surface would be lighter in color.

  25. Damien Evans

    That’s a great example of good science in action

  26. Tom

    It seems to me we should have the ability to check this kind of thing our first hand, instead of having to model it in computers and take our “best guess.” Why can’t we plant an automated rover factory on one of the martian moons and start dropping them all over the surface? Hold some in reserve, in orbit, ready to check out any interesting discoveries as necessary.

    Honestly, when I look at Phobos and Deimos, I just see raw material, and considering the relative cost of flying out a single rover vs. a rover factory…

  27. Tom Marking

    “Tom — the surface material should be darker than that underneath due to chemical weathering and accumulations of dark iron or manganese oxides (ie. desert varnish on Earth deserts). The granular material underneath the surface would be lighter in color.”

    I’m not sure what is being claimed in the new report. Is it claiming that the plume is really subsurface material that is lighter in color and we can see it due to the overlying darker material being blown away or falling down the hill? If so then there are several questions we might want to ask such as is the direction of the plume in the same direction as the prevailing winds? Or can we see where the darker material fell to down the wall of the crater? It’s been a while since I read the article about the original discovery but as I recall they had several reasons to believe the plume was deposited by running liquid.

  28. Tom Marking

    http://www.nasa.gov/mission_pages/mars/news/mgs-20061206.html

    .
    .
    .
    “The shapes of these deposits are what you would expect to see if the material were carried by flowing water,” said Michael Malin of Malin Space Science Systems, San Diego. “They have finger-like branches at the downhill end and easily diverted around small obstacles.” Malin is principal investigator for the camera and lead author of a report about the findings published in the journal Science.

    The atmosphere of Mars is so thin and the temperature so cold that liquid water cannot persist at the surface. It would rapidly evaporate or freeze. Researchers propose that water could remain liquid long enough, after breaking out from an underground source, to carry debris downslope before totally freezing. The two fresh deposits are each several hundred meters or yards long.

    The light tone of the deposits could be from surface frost continuously replenished by ice within the body of the deposit. Another possibility is a salty crust, which would be a sign of water’s effects in concentrating the salts. If the deposits had resulted from dry dust slipping down the slope, they would likely be dark, based on the dark tones of dust freshly disturbed by rover tracks, dust devils and fresh craters on Mars.

    .
    .
    .

  29. Tom Marking

    “It seems to me we should have the ability to check this kind of thing our first hand, instead of having to model it in computers and take our “best guess.” Why can’t we plant an automated rover factory on one of the martian moons and start dropping them all over the surface?”

    I agree that it’s best to check these things out up close and personal. Your automated rover factory stationed on Phobos sounds suspiciously similar to a Von Neumann probe or a Bracewell probe. I’m not sure our present technology is up to building one of these things yet. Maybe in the future we will be able to do this but at the moment each rover mission is $200 million apiece.

  30. Tom Marking

    http://www.physorg.com/news123491857.html

    .
    .
    .
    “It rules out pure liquid water,” said lead author Jon D. Pelletier of The University of Arizona in Tucson
    .
    .
    .
    They added that their research does not rule out the possibility that the images show flows of very thick mud containing about 50 percent to 60 percent sediment. Such mud would have a consistency similar to molasses or hot lava. From orbit, the resulting deposit would look similar to that from a dry avalanche.
    .
    .
    .

    So the Pelletier study is not ruling out liquid water at all, just pure liquid water. Well, duh. I doubt pure liquid water could even travel 100 meters without evaporating first in a 0.006 atm atmosphere. Who claimed that it was pure water? Certainly not Malin.

  31. Tom Marking

    http://www.msss.com/mars_images/moc/2006/12/06/gullies/not_dust/index.html#Fig1a

    Why the New Gully Deposits Are Not Dry Dust Slope Streaks
    MGS MOC Release No. MOC2-1621, 6 December 2006

    There are many excellent images on this page which compare the gully deposits versus slope streaks which are common on Mars.

    “In developing geologic interpretations from inspection of images, many factors are considered: size, relief, shape and pattern, color or brightness, texture, and association (context). Context is often the final discriminator between features that look similar. It is undeniable that the gully deposits resemble slope streaks, but they do not share the same context. If they are slopes streaks formed by downslope movement of dry, unconsolidated dust, then they are extremely rare features, because the new gully deposits (a) do not occur in regions where slope streaks occur, (b) are not found near any dark slope streaks, while typical light slope streaks have dark ones nearby, and (c) formed during the MGS MOC mission, while no new light slope streaks were observed to have formed anywhere else on the planet during the mission. Conversely, their presence within craters with gullies and the existence of similar light-toned features on other gullied (and in some cases on adjacent) slopes, with which they share geomorphic attributes, may be coincidental but is probably not. The gullies themselves provide the context for the gully deposits, and argue for a genetic relationship.”

  32. Chris

    I’m not surprised that this wasn’t water. It’s hard for me to sort out what the mainstream media is saying about water on Mars and what the researchers and respectable scientists are saying.

    I know that Mars has large areas of Olivine on the surface. From what I understand this mineral readily weathers in water. I don’t know how quickly it weathers. In decades, millenia, or millions of years? I don’t know when it formed before or after a supposed Mars wet period. Does this put an upper limit on how much water Mars has or had? http://www.psrd.hawaii.edu/Nov03/olivine.html

    I think we should explore Mars just for the sake of exploring Mars, not to look specifically for water (and life). Because if it’s hyped that Mars was very wet (and by implication could have harbored life), and it turns out that Mars was never very wet nor very hospitable for life then I think we lose public interest and support. We can learn as much about the Earth by contrast in studying Mars as by what the two worlds have in common. Discovering liquid water and life on Mars would be icing on the cake.

    I’m more inclined to accept that Mars was damp but not wet. Any pointers to more info would be appreciated.

  33. It should be noted that whatever created the recent bright deposits and the older gullies could be two completely different things. So the deposits might be just dust slides, but that doesn’t take away from the fact that the _gullies themselves_ were most likely, from the reports I’ve read, originally created by water, even if a long time ago.

    Paul

    The Meridiani Journal
    a chronicle of planetary exploration
    http://web.mac.com/meridianijournal

  34. Douglas Watts

    I recommend taking low-res jpegs off the Internet, blowing them up to 800 percent on Photoshop, jacking up the “saturation” control, and wildly speculating.

    But that’s just me …

    Cheers.

  35. The Wiccan Scientist,

    There’s another problem with voyages to Europa — it’s right smack in the middle of Jupiter’s radiation belts.

    Contaminating the ocean is probably not an immediate issue, since the ocean, if present (and it probably is), would be about 50 km beneath the ice. Humanity has never dug a hole that deep and may never do so.

  36. sean d

    everbody say it with me we don’t know!

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