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Mars Earth NASA Space Science

Flowing Water On Mars' Surface May Just Be Rolling Sand Instead (theverge.com) 81

Two years ago, NASA made a big splash when it announced the discovery of flowing water on the surface of Mars. Unfortunately, according to new research from the U.S. Geological Survey, the surface features that NASA thought were made up of liquid water may actually be flowing grains of sand instead. The Verge reports: The features in question are dark streaks that show up periodically on Martian hills, known as recurring slope lineae, or RSLs. When one of NASA's spacecraft, the Mars Reconnaissance Orbiter, studied these lines more closely, it found that the RSLs were made up of hydrated salts -- meaning they were mixed with water molecules. At the time, NASA thought that was significant evidence that flowing liquid water caused these bizarre streaks. But researchers at the USGS say these features look identical to certain types of slopes found on sand dunes here on Earth. Those slopes are caused by dry grains of sand flowing downhill, without the help of any water. It's possible the same thing is happening on Mars, too. Since liquid water is key for life here on Earth, many thought these strange lines of flowing water may help support life on the Martian surface. But now these RSLs may not be the best place to look for life anymore.
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Flowing Water On Mars' Surface May Just Be Rolling Sand Instead

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  • by Frosty Piss ( 770223 ) * on Thursday November 23, 2017 @02:40AM (#55609221)

    Well that does it, I'm out.

  • ... that explains why Mick Jagger looks like he does. He and his mates must have grown up on Mars!

  • Given the atmospheric pressure, and the temperature, it was highly unlikely that they had any flowing liquid water anyway.

    • by doctorvo ( 5019381 ) on Thursday November 23, 2017 @04:17AM (#55609425)

      Liquid brines are not only plausible under Martian conditions, they have been reproduced experimentally [nih.gov].

      Given the presence of large amounts of calcium perchlorate (eutectic point -74C), there are almost certainly liquid reservoirs of brine somewhere on Mars, the only question is how big they are and where/when they are exposed to the surface.

      • by Rei ( 128717 )

        The whole discussion has always seemed more academic to me than anything else. Deliquescent perchlorate brine concentrates aren't somewhere you'd look for life, they're something you'd use to sterilize a surface. Even normal levels in Martian regolith are probably enough to slowly burn your skin from handling it, in a manner akin to lye. [nasa.gov]

        • by Anonymous Coward

          That's missing the point. The calcium perchlorate deposits suggest that large bodies of water previously existed. Pointing out that life is unlikely to form in highly-concentrated caustic salt solution is odd because nobody proposed that in the first place.

          • by Rei ( 128717 )

            That's not true; Mars's perchlorates are believed to be due to the same process that forms perchlorates in places like the Atacama, just on a much larger scale: UV-driven gas-phase oxidation of volatile chlorine species (such as HCl) and/or chlorine-bearing aerosols in cold, exceedingly dry environments.

            The fact that Mars was once wet has nothing to do with its present perchlorate inventory.

          • by Mr D from 63 ( 3395377 ) on Thursday November 23, 2017 @07:59AM (#55609903)
            There is clearly (and understandably) a desire in the scientific community to find as much evidence of water on mars as possible. More water means higher chance of life and better chance of human colonization support. I think its possible the scientific community was biased toward a water flow explanation, or possibly that's just the one the media stuck to. Did they work as hard to prove other explanations? I'm not sure they did, but this story is evidence that they are doing just that.
            • I think its possible the scientific community was biased toward a water flow explanation, or possibly that's just the one the media stuck to. Did they work as hard to prove other explanations? I'm not sure they did, but this story is evidence that they are doing just that.

              You're making the mistake of equating what's published with some measure of scientific truth. The scientific literature is a place for debate, not truth. You can't have a debate if you insist that everything everybody says is known to be t

              • You're making the mistake of equating what's published with some measure of scientific truth.

                No, I clearly said "or possibly that's just the one the media stuck to". I never said anything to equate what is published with scientific truth. And I never ' insist(ed) that everything everybody says is known to be true".

                You can't have a debate putting words in the mouths of others.

                • You can't have a debate putting words in the mouths of others.

                  I'm not putting words in your mouth, I'm trying to explain to you where you misunderstand how science operates. Scientists are biased, in terms of what they work on, in terms of what they believe to be true, and in terms of what they publish; you don't need to look for "evidence" of that, it's part of the process. That's why the scientific literature is full of papers that provide incorrect explanations and incorrect results; the literature is pr

                  • You can't have a debate putting words in the mouths of others.

                    I'm not putting words in your mouth, I'm trying to explain to you where you misunderstand how science operates. Scientists are biased, in terms of what they work on, in terms of what they believe to be true, and in terms of what they publish; you don't need to look for "evidence" of that, it's part of the process. That's why the scientific literature is full of papers that provide incorrect explanations and incorrect results; the literature is probably biased towards such papers.

                    I don't misunderstand how science operates. I never claimed bias plays no role in science, that is your twist. I merely pointed out a specific bias. It is YOU who put words in my mouth and took that as some misunderstanding or commentary on bias in science in general.

                    Biases in science are not always helpful. Pointing out biases can be very helpful. Sorry I pointed a potential one out. Why do YOU misunderstand how that can be helpful?

                    • Sorry I pointed a potential one out. Why do YOU misunderstand how that can be helpful?

                      And I keep telling you: your reasoning was wrong and you misidentified the bias. You said "I think its possible the scientific community was biased toward a water flow explanation" as an explanation for why a paper was published postulating water flow when new interpretations contradict that. In actual fact, the scientific community is, if anything, biased against, not towards, a water flow explanation.

                      That is, your reason

                    • And I keep telling you: your reasoning was wrong and you misidentified the bias. You said "I think its possible the scientific community was biased toward a water flow explanation" as an explanation for why a paper was published postulating water flow when new interpretations contradict that.

                      Your seeming desire to tell me I don't understand science is clouded by your lack of reading comprehension. I did NOT say the bias was an explanation for why 'a' paper was published. Rather, the bias "could" explain the propensity to look at water first and focus on water based explanations.

                      Then, I followed with; "but this story is evidence that they are doing just that.", working hard to prove other explanations. In other words, the bias, if it exists, did not in the end prevent them from considering ot

                    • Well, I think both your original statement and your level of understanding of science are pretty clear. We'll just have to live with having a low opinion of each other.

        • Deliquescent perchlorate brine concentrates aren't somewhere you'd look for life, they're something you'd use to sterilize a surface

          Actually, the presence of perchlorates is good news for the possibility of life on Mars [space.com].

          • by Rei ( 128717 )

            The "safe drinking level" for perchlorate in water on Earth for a 70kg human is 32 parts per billion. The average level of perchlorates in Martian regolith is half a percent, and the hypothetical perchlorate brines were "perchlorate salts containing only the minimum amount of water to make them flow". Even bacteria do not survive in such perchlorate concentrations (only the hardiest of species can handle the half a percent found in average regolith, let alone concentrated brines). Heck, Martian regolith

            • The "safe drinking level" for perchlorate in water on Earth for a 70kg human is 32 parts per billion.

              Perchlorate is so toxic to humans because of specific protein interactions (mostly, that it blocks an iodide pump in the thyroid). Giving this example in a discussion of perchlorate effects on bacteria is downright stupid.

              The average level of perchlorates in Martian regolith is half a percent, and the hypothetical perchlorate brine ...

              Terrestrial bacteria have not had any need to adapt to perchlorate brines,

      • by phayes ( 202222 ) on Thursday November 23, 2017 @07:50AM (#55609875) Homepage

        This Ars Technica article [arstechnica.com] was much more informative than the cited sources.

        Brines evaporating should have left detectable level of salt deposits which we are not seeing.

        That said, if it is sand, we should also be seeing a build-up of these darker sands at the bottom of the slopes which we are not seeing either.

        Clearly we are missing something that a visit would resolve.

        • by Strider- ( 39683 )

          That said, if it is sand, we should also be seeing a build-up of these darker sands at the bottom of the slopes which we are not seeing either.

          A possibility, though, is that the sand is weathering once exposed to the Martian atmosphere. I don't know what the chemical process would be. All it would take is a change to the composition of the material directly on the surface, and it would look different from above.

          • by phayes ( 202222 )

            I didn't want to quote too much from the Ars article (which along with the comments is as usual more insightful that comments here on /.) but:

            But even the authors admit there are some problems with this idea [of solid sandy traces & not water]. To begin with, when a slope destabilizes and some of the material flows downhill, the largest particles should flow the farthest. This should leave the slope in a more stable state and less likely to have RSL appear the Martian year following; instead, they seem to reappear in the same places.

            Then there are color issues. Darkening could be ascribed to the uncovering of material that hasn't been lightened by its exposure to harsh Martian conditions. But many of the RSL show a complicated pattern of darker and lighter features. In addition, there's no obvious mechanism to lighten the RSL back up again in less than a single Martian year. The review suggests a coating of dust might help, but there would have to be additional factors involved.

            Finally, like the salt left behind by evaporated brines, the downward flow should leave piles of material at the base of the slope and near any features like boulders that protrude from it. But there's no sign of that in most of the images. So, based on these issues, the idea that these are granular flows has nearly as many problems as the watery explanation.

            So where does that leave us? The paper argues that we're right back where we started: we don't expect liquid water on the surface of Mars, and the RSL simply aren't conclusive evidence of it. "Flowing liquid water in the current Martian climate has always been an extraordinary claim," the authors write. "The observations and interpretations presented here suggest that RSL are no longer extraordinary evidence." As long as we're not sure what they are, they can't be used as evidence of anything else.

    • Yes and it was a well known fact decades ago. This water-on-Mars affair was the usual publicity stunt to get more funds from the government with pseudo-science (because real science makes the headlines rarely). It is a fact that Venus is the more earth-like planet inside the solar system (and probably even beyond the solar system), however since studying Venus is too costly and complicated we got this Martian frenzy.
      • > It is a fact that Venus is the more earth-like planet inside the solar system

        By mass and gravity. The surface and atmospheric conditions on Mars are closer to Earth than those of Venus, by a longshot. Mars, for instance, has remnants of a magnetic field, Venus doesn't. Mars has an average temperature of -60c, Venus is 462c. Mars has a surface pressure of 600mbar. Venus has a surface pressure of 93bar. The Martian atmosphere is mostly CO2, as is that of Venus... but Venus also has sulfuric acid. A

        • If you ask me which rock is more like Earth, for anything other than mass and density I'll choose Mars.

          Other than mass, density (which is also related to the composition of the planet) and distance from sun, that is everything. Saying that Mars is more like Earth than Venus is like saying that a chimpanzee is more similar to George Clooney than an amputee, because both the chimpanzee and George Clooney have two legs and two arms. In fact, like a chimpanzee could never be a human being (like George Clooney), Mars could never be a life supporting (that is Earth-like) planet because it is too small (hence no at

  • They’ve been sending probe after lander after probe for decades now trying to prove there is or once was life on Mars. The battle between Science and Religion played out across the planets. Like the believers would ever be dissuaded by any scientific facts.
    • Re: (Score:2, Interesting)

      by Anonymous Coward

      They’ve been sending probe after lander after probe for decades now trying to prove there is or once was life on Mars. The battle between Science and Religion played out across the planets. Like the believers would ever be dissuaded by any scientific facts.

      There is an international agreement on not contaminating Mars until we know that there isn't life there.
      If you are sure that there isn't life on Mars then it is still of interest to prove it so that future missions there doesn't have to worry about it.

      (Unfortunately saying that there isn't life on Mars is a bit like saying that there isn't a God. There is always another rock you haven't looked under so he might be there. You can only prove that something exist, not that it doesn't.)

    • You do realize the existence or non- of life elsewhere has no bearing on religion? The Catholics already have set up a protocol if any is found.
      • You do realize the existence or non- of life elsewhere has no bearing on religion? The Catholics already have set up a protocol if any is found.

        The battle I was talking about will certainly get hotter if life is discovered independent of the earth. It would certainly advance the cause of evolution and science in general with people open to new facts, at least.

  • this isn't news (Score:4, Interesting)

    by doctorvo ( 5019381 ) on Thursday November 23, 2017 @03:58AM (#55609409)

    People already knew that sand/dust can cause similar features. They believed (and still believe) that this is indicative of flowing water because of seasonality, temperatures, and association with hydrated minerals. We won't know for certain until we observe flowing water more directly, of course.

  • Living in Canada, I have often observed the interesting patterns in dry snow lying on the ground caused by stiff winter breezes over a period of several days. And sometimes when I have seen photos of "evidence of water on Mars", the similarities to wind patterns in our snow has seemed obvious. Fine sand and ordinary dry snow probably have pretty similar aerodynamic responses. Add to this the fact that sand is much more abrasive than snow and you have the possibility of Martian sand causing gradual change
    • > I wonder why these similarities and possibilities have never been considered in the drive to prove that water existed or exists on Mars.

      I'm just going to throw this out there - when you're talking about dynamic activity on another planet... the people doing this research have not only considered those things, but done their best to model them to an infinite number of decimal places.

      They're looking for life, and the best way we know of to find it is to look for liquid water. So they look for possible (

    • My understanding is that the sand rolling down hypothesis is strange because if sand does roll down and not accumulate at the bottom of the roll, where is it?

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