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Mars NASA Space Science

Martian Gullies Explained By ... Sand 97

Posted by CmdrTaco
from the well-thats-not-'as-much-fun dept.
eldavojohn writes "There's a lot of evidence that a very long time ago some fluid once flowed on Mars, but the primary evidence of water today — gullies inside craters — is explainable by a much less exotic reason: flowing dust and sand. It would now seem that the news from 2006 that NASA had found definitive evidence of flowing water on today's Mars needs to be comprehensively reexamined. The Bad Astronomer lays claim that flowing sand and dust doesn't explain all recent hi-res imagery from the red planet, but it certainly does seem more plausible, considering what we know about Mars."
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Martian Gullies Explained By ... Sand

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  • YEAH RIGHT! (Score:4, Funny)

    by Gerafix (1028986) on Tuesday May 04, 2010 @11:59AM (#32086290)
    That's what the Martians want us to think. Next they're going to try and contaminate our precious bodily fluids.
    • Re: (Score:3, Insightful)

      by mu51c10rd (187182)

      to try and contaminate our precious bodily fluids.

      We do that well enough ourselves already...no need for Martians to bother.

      • by Anonymous Coward
        I think when we determine, once and for all, that there is or is not water on Mars, then all of human suffering will come to an end. I propose that we increase taxes and spending to their very limits so that we resolve this crisis as rapidly as possible. We should divert all available resources to this matter, including seizing all ore mines and drafting of engineers to support the program. Anyone who shows any potential to be able to do math or computer science should be taken from whatever it is they a
        • Re: (Score:1, Funny)

          by Anonymous Coward

          Is it hard posting to Slashdot while volunteering at the soup kitchen?

    • Re: (Score:1, Funny)

      by Anonymous Coward

      On no account will a Martian ever drink water, and not without good reason.

    • Re: (Score:1, Funny)

      by Anonymous Coward

      That's what the Martians want us to think. Next they're going to try and contaminate our precious bodily fluids.

      Too late! They already have floridated the water!

    • by mjwx (966435)

      That's what the Martians want us to think. Next they're going to try and contaminate our precious bodily fluids.

      What makes you think we want your fluids monkey. We have already abducted the one designated Paris Hilton and have sequenced the DNA of half your race.

  • Oh yeah? (Score:4, Funny)

    by clang_jangle (975789) on Tuesday May 04, 2010 @12:00PM (#32086300) Journal
    Oh yeah, smart guy? Then answer this:

    WTF do the Martians drink?
  • by Monkeedude1212 (1560403) on Tuesday May 04, 2010 @12:01PM (#32086322) Journal

    Have they found the soundstage on mars where they faked the moon landing?

  • Water, microbes, can we fill it with CO2, no ionosphere, how do we colonize...

    Seriously. The only way to deal with Mars is to divert the asteroid belt's mass towards it to increase its mass. Force several tens of thousands of asteroids into a decaying orbit such that the mass is deposited on the planet. There's no water there, it all evaporates away without enough gravity to hold an atmosphere and enough pressure to remain liquid!

    • Re:Terraforming (Score:5, Interesting)

      by heck (609097) <deadaccount@nobodyhere.com> on Tuesday May 04, 2010 @12:08PM (#32086440)
      The only way to deal with Mars is to divert the asteroid belt's mass towards it to increase its mass. Force several tens of thousands of asteroids into a decaying orbit such that the mass is deposited on the planet. There's no water there, it all evaporates away without enough gravity to hold an atmosphere and enough pressure to remain liquid!

      Mass is not the issue; the lack of a magnetosphere is. Without a magnetosphere, the solar wind will strip the atmosphere, leaving you in the same state. We would need to provide some means of creating a field which shields the atmosphere from solar winds.

      Did a quick google to find an article - this one was published in 2010: http://science.nasa.gov/science-news/science-at-nasa/2001/ast31jan_1/ [nasa.gov]

      • by heck (609097)
        Yes I meant 2001. Crap. (Um, intentional reference to two of Arthur C Clarke's works. Yeah, that's it!)
      • by roman_mir (125474)

        Magnetosphere is easy, all you need to do is

      • Re: (Score:3, Interesting)

        by Brett Buck (811747)

        Well, if you crash a bunch of asteroids into it, it will likely become molten, creating a new phase of differentiation, and there is a reasonable chance that a new dynamo will form and create a new magnetosphere. It's at least as plausible that that would happen as you could crash a bunch of asteroids into it in the first place. It wouldn't likely last all that long in geological terms given the likely lack of useful radionuclides.

        • If you can move that much material around space, you could alter the orbit of Mars to bring it closer to Earth. Ok, that still wouldn't help with the magnetosphere but once you're moving planets, you can hollow them out and have a roaming planetship.

    • I think one of the bigger issues is that Mars doesn't have a molten core, and therefor, not much of a magnetic field. We already know that Nuclear reactions can cause bad radiation, and that the core of the sun is constantly going through nuclear reactions. As such, a lot of radiation gets shot towards Earth, but because our planet has a magnetic field a lot of it gets reflected or refracted away. This is what causes the Northern lights.

      So, I mean, should we get air on Mars, we'll still probably get bombard

      • by Yvan256 (722131)

        So, I mean, should we get air on Mars, we'll still probably get bombarded with Beta Particles.

        But that would be a perfect place to build a super-heroes training camp!

      • by mbone (558574)

        I think one of the bigger issues is that Mars doesn't have a molten core,

        Mars does have a molten core, which was shown by the combination of Viking and Pathfinder [harvard.edu] tracking data.

        I am pleased to say that I helped get make those finding possible, by going to various people at JPL with a colleague (Bruce Bills) and pressing all and sundry to get the DSN to range to Pathfinder after landing, specifically to improve the precession constant and determine this.

      • by mbone (558574)

        not much of a magnetic field

        Well, that is an interesting point. It has a liquid core. It has a fair amount of magnetization of its surface [usra.edu].

        So, it had a magnetic field, presumably from a core dynamo like the Earth's. To me, the question is, did the core dynamo die some long time ago, or is Mars currently undergoing a magnetic field reversal, as the Earth does regularly (i.e., was had a billion years ago, or a few thousand) ? The vast consensus is that the Mars magnetic field died a long time ago, but I think

      • by sznupi (719324)

        Don't equate nuclear reactions = bad radiation so readily in this case. Photons which start as gamma rays in the Sun core are in the spectrum around visible light when finally emitted towards us. Sure, also quite a lot of UV there...but that's not the most problematic element of "space radiation".

        That would be the stream of energetic particles; "solar wind". Mostly a result of good old heating and interactions with magnetic fields in the solar atmosphere.

    • by Gerafix (1028986)
      Why do we have to live on the surface? Let's move in underground, should be plenty of room and my impression is the geology is fairly stable although I could be wrong.
    • Re:Terraforming (Score:5, Informative)

      by CrimsonAvenger (580665) on Tuesday May 04, 2010 @12:27PM (#32086854)

      The only way to deal with Mars is to divert the asteroid belt's mass towards it to increase its mass.

      If the entire Belt were diverted to Mars, it would increase Mars' mass by about 1%.

      In other words, "your idea is silly"....

    • by d1r3lnd (1743112)

      Hey guys, let's take the most easily accessible resources in the solar system and then drop them into the giant fucking gravity well of a planet we don't live on.

      Awesome plan, dude.

      • The most useful resources there are nickel-iron, made of two highly common elements easily mined on earth for cheap.
  • It's a shame that our evidence for water turned out to likely be false, but that shouldn't stop us from continuing to look. We're not going to be travelling to Mars until at the earliest the '30s, so there's no real rush.
    • by Anne_Nonymous (313852) on Tuesday May 04, 2010 @12:10PM (#32086482) Homepage Journal

      Forget water. If you want to create a space stampede to Mars, announce the discovery of oil there.

      • Re: (Score:3, Insightful)

        by JoshuaZ (1134087)
        Well, that would make scientists ecstatic also. Oil means there was life in the past. Enough life to produce oil would upset a lot of models and make things very interesting. I doubt that the discovery of oil on Mars would actually cause industry to be that much more interested than they would be now. The energy cost of moving the oil back to Earth would probably be much larger than that gained from getting the oil. I'm not even sure it would make industry much more practical on Mars since there's not much
      • Do you realize the implication of oil being there? That would mean that once there was life there! ^^

  • Is it potable?

    I know that was the entire basis for one of the Doctor Who specials, but, do we even know how hard it would be to make it potable where it not to be drinkable?

  • by SnarfQuest (469614) on Tuesday May 04, 2010 @12:16PM (#32086632)

    Take those photos that the various missions have taken of Mars, and use the photo analysis software that CSI uses. You should be able to look at things down to a molecular level then. Even a photo taken with a disposable camera that happened to be pointing in the direction of Mars during a stormy night should be sufficient to determint the location of all water on Mars. They could look at the back side of Mars based on a reflection from one of the stars behind it, so you should easily have 360 degrees of visibility..

  • by Yvan256 (722131) on Tuesday May 04, 2010 @12:18PM (#32086658) Homepage Journal

    Nutrition Facts: Mars Bar

    Calories: 220
    Sodium: 70 mg
    Total Fat: 9 g
    Potassium: 0 mg
    Saturated: 6 g
    Total Carbs: 36 g
    Polyunsaturated: 0 g
    Dietary Fiber: 1 g
    Monounsaturated: 0 g
    Sugars: 30 g
    Trans: 0 g
    Protein: 2 g
    Cholesterol: 5 mg
    Vitamin A: 0%
    Calcium: 6%
    Vitamin C: 0%
    Iron: 4%

    Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.

  • by molo (94384) on Tuesday May 04, 2010 @12:24PM (#32086782) Journal

    The ESA already has a picture of water ice in a martian crater. Maybe they are talking about different types of craters in different regions, but this photo clearly shows that it is possible.

    http://www.esa.int/SPECIALS/Mars_Express/SEMGKA808BE_0.html [esa.int]

    -molo

  • by AlgorithMan (937244) on Tuesday May 04, 2010 @12:34PM (#32086984) Homepage
    http://antwrp.gsfc.nasa.gov/apod/fap/image/0504/WaterOnMars2_gcc_big.jpg [nasa.gov] this was really published by NASA a couple of years ago... on April 1st...
    • Sorry, I don’t follow links, that have “fap/image” anywhere in their name. Especially if they come from NASA. ;)

      P.S.: (I prefer videos. ;)

  • by ErikTheRed (162431) on Tuesday May 04, 2010 @12:49PM (#32087224) Homepage

    This actually hits on one of my personal bugaboos - scientists that claim to know something "definitively" while the research or hypothesis is still warm from the metaphorical oven. Unfortunately, the institutions that employ them have figured out that you can get funding through "science by press release" - the initial press release gets the headlines; the retractions are hardly noticed (except on Slashdot). The scientists themselves are certainly culpable as well for going along with this - they should know better. Only a small percentage of theories stand the test of time. Yes, I understand that it's 2010 and we all want answers right now, dammit, but 99.99% of the time life just doesn't work that way.

    So anyway, "definitively" - You keep using that word. I do not think it means what you think it means.

    • Re: (Score:2, Funny)

      by MathiasRav (1210872)
      They're definitely doing it on purpose.
    • The scientists don't write the press releases. They dont exercise editorial oversight, they don't choose the headline. That's the science press, and they are to blame.

      Now, some scientists do get quoted for making statements that are too strong, but the press is like the National Enquirer: If they can't get you to make some ridiculous claim, they will find someone who is desperate enough to do so.

      The solution: Don't read science press releases or newspaper articles - read the actual peer-reviewed articles

      • by H0p313ss (811249)

        The scientists don't write the press releases. They dont exercise editorial oversight, they don't choose the headline. That's the science press, and they are to blame.

        Which makes me wonder what the comparative rate of alcoholism is between scientists whose research is (badly) publicized and those which are not.

    • by Chris Burke (6130) on Tuesday May 04, 2010 @02:17PM (#32088598) Homepage

      This actually hits on one of my personal bugaboos - scientists that claim to know something "definitively" while the research or hypothesis is still warm from the metaphorical oven.

      And one of my personal bugaboos is people getting their panties in a twist over scientists claiming something that they're not and never have actually claimed.

      The word "definitive" appears nowhere except in this slashdot summary. It does not appear in the previous slashdot summary that the offending word links to, nor does it appear in the article that slashdot summary links to either, and certainly does not appear in the original statement by the scientists. In fact, the article says that more work needs to be done to determine if what they discovered was definitely water.

      So basically your whole rant about "science by press release" is baseless slander because you assumed a word in a /. summary twice removed from the original source was the actual word used by scientists, rather than click a couple links and learn that you were wrong.

      Good job.

      • by bit01 (644603)

        "If this was coming down the slope [toward you], you'd want to get out of the way," said NASA's Kenneth Edgett, a scientist with Malin Space Science Systems. "This is the squirting gun for water on Mars"

        And numerous other similar comments by the scientists involved.

        So basically your whole rant about "science by press release" is baseless slander

        Actually, it's the "scientists" who should be reprimanded.

        In fact, the article says that more work needs to be done to determine if what they discovered was def

        • by Chris Burke (6130)

          And numerous other similar comments by the scientists involved.

          Yeah like "water seems to have flowed".

          One cop-out sentence at the end of the article does not somehow make it okay when the basic thrust of the article was the exact opposite.

          Some people love to put obscure modifiers in the small print and pretend that that justifies a dishonest main article/ad/whatever. It doesn't.

          It wasn't at the end of the article, it wasn't small print, it was right in the middle of the article and you know it. And there's

    • Re: (Score:3, Informative)

      by DM9290 (797337)

      The original press release did not say anything about "definitive" evidence of water. In fact it said:

      "Certain tasks remain, according to the panelists. For example, a spectrographic analysis of the “white stuff,” to prove that it is definitely water. These might be carried out by the Mars Reconnaissance orbiter, recently arrived in order to replace the aging Global Surveyor.
      "

      So the original report said something looks like water. It isn't just a flow of dust.

      And the current summary is WRONG. Th

    • Re: (Score:3, Interesting)

      by B1oodAnge1 (1485419)

      The more time I spend in college the more I realize that nearly everything that we "know" is really just semi-educated guesses.

      In my experience this applies to just about every science except perhaps math.

  • by SpaceMika (867804) on Tuesday May 04, 2010 @01:06PM (#32087544)

    I love that "above some critical threshold" is listed like a mysterious or complex thing. It's the angle of repose, the angle that a material naturally sits at when you let it fall from a height and pile up. It might be, if things are very complicated, the angle of repose + cohesion, but then you're back at water-based theories again since water is the easiest way to remove cohesion and trigger failure.

    I also really like that the experimenters managed to recreate a sand flow in their lab. Of course they did. The field of prior research involving laboratory sand flows is immense, especially if you start including the ones with tiny glass beads of carefully varied diameters instead of sand. The only problem is thioxtropy -- landslides are renowned for having material that exhibit viscosity inversely proportional to velocity -- which is not easily replicable in small-scale lab settings.

    I'm not sure if this is a, "Physicists discover what geologists already knew" moment, or a "Journalists are puzzled by the mundane mysteries of science," or what, exactly, but if you want to learn more about landslides on Mars, check out geotechnical journals starting with Lucchitta 1978 (Bulletin of the Geological Society of America, v89, pg 1601) and work your way forward. As the lunar and Martian landslides discredited an entire set of excess mobility theories, they're very well described and discussed.

    • by blueg3 (192743)

      The journalists read or had described to them the research, and arbitrarily picked (based on what seemed interesting or novel to them) parts to talk about. Science journalists rarely have any real understanding of which parts of research are actually novel and which aren't. Of course, they can repeat (badly) the summary "what these results mean", but when talking about the methodology, unless the scientist is careful to point out which parts are novel, they never get it right. Since a lot of the more intere

  • How come every announcement by NASA has you going away saying 'Ah Well." Should be called NAWA
  • Martian Water (Score:5, Informative)

    by mbone (558574) on Tuesday May 04, 2010 @01:37PM (#32088032)

    From the original blog post : "over this timescale, the Martian atmosphere has been too cold and thin for liquid water."

    I read something like this frequently, and yet it is simply wrong and I wish people would stop repeating it.

    Liquid water is not magic, but governed by physics. For there to be liquid water on Mars, all that is needed is that water be present, that the surface pressure be above the triple point of water, and that the temperature be above the freezing point. (Actually, this can be relaxed somewhat for brines and the like, but let's put that aside for the moment.) We know that Mars has water. What about the other two conditions ?

    Much of the surface of Mars is above the triple point of water (i.e., at a low enough elevation that the surface pressure is higher than 611.7 pascals). Any low lying region is. The Viking 2 landing site is (some of the time) and the Phoenix landing site is (all of the time). The entire Hellas basin is, and it is highly likely to have liquid water at times (as the surface temperature there is warm enough during the day). Remember, peak surface soil temperatures on Mars can reach 27 C, even under current climate conditions.

    Further, the atmospheric pressure on Mars varies greatly during its obliquity cycle, and it is highly likely that the entire planet (except for the high volcanoes of Tharsis) can support liquid water at times during each obliquity cycle. During those phases of the cycle, the atmospheric temperatures will be generally warmer, as well.

    Now, this does not prove or disprove that these gullies are formed by water rather than sand, but you don't need unusually strong brines or geothermal vents to have liquid water on Mars (even though both of those probably exist as well), and it is quite reasonable to expect its presence in places, even under current atmospheric conditions.

    • Re:Martian Water (Score:4, Interesting)

      by SpaceMika (867804) on Tuesday May 04, 2010 @02:46PM (#32089036)

      I share your exasperation with the lack of popsci understanding of Mars' variable temperatures & pressures.

      When I used to run planetarium shows for kids, I used to explain the temperature gradient by telling them, "If you stood on Mars, you'd wear sandals and a parka, since your feet would be as warm as a summer day but by the time you reached your head it'd be colder than winter in Antarctica!" which, although on the "tiny lies of oversimplification" side, is true-ish and a vivid enough image that they remembered months later.

  • It means in future we can migrate to Mars. http://cleancolonpro.net/ [cleancolonpro.net]
  • The paper in this article is pretty interesting, but I don't think it explains the newest features seen in these gullies; the way they terminate in the sand looks more like a liquid flow than solid [discovermagazine.com]. I suspect that the authors can explain many gullies on Mars, but not all the gullies. There may be more than one mechanism at work here!
  • This comment [technologyreview.com] on the article at Technology Review challenges the conclusions reached. Quoted below; I've added in square brackets a couple of little elaborations of terms.

    We've Been Down This Road Before
    This model suffers from the same problem as the dry gully hypothesis put forth by Shinbrot et al. (2004) (http://www.pnas.org/content/101/23/8542.abstract [pnas.org]). Yes, you can get an alcove and an apron, but it's missing the key defining characteristic of gullies, which is the channel. Their experiments did not p

  • Sand is a fluid ..... so a fluid still flows on Mars ....

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