Mars Gullies Produced by Dry Granular Debris and Not by Recent Water Flow

Article written: 1 Mar , 2008
Updated: 26 Dec , 2015

The High Resolution Imaging Science Experiment (HiRISE) on board NASA’s Mars Reconnaissance Orbiter (MRO) observed what appeared to be fresh gullies formed by a rapid release of water on the Martian surface in 2006. However, new computer models simulating the creation of gullies on the surface of Mars suggest that they are in fact created by the flow of dry debris (i.e. landslides) and not by the flow of water. A blow for the microbial life hunters and a huge blow for mission planners looking for easy sources of water for manned missions…

The MRO isn’t the only orbiter to view apparent gullies forged by spurts of water. The Mars Orbiter Camera (MOC) onboard NASA’s Mars Global Surveyor (MGS) also made news in 2006 when scanning the cratered regions of Terra Sirenum and Centauri Montes. Images taken several years apart revealed some changes in the most recent pictures, highlighting what looked like outflow channels from surges of liquid water (pictured below). What made this especially exciting was that this was possible evidence for the existence of liquid water flowing on Mars within the past few years (albeit very quickly).
Before and after pictures by MOC of a gully inside a crater (credit: NASA/JPL)
New work by scientists at the University of Arizona appears to conflict with these observations. In an attempt to demonstrate the characteristics of water flowing in Martian conditions, Associate Professor Jon D. Pelletier (Geophysics) and colleagues used topological data from the HiRISE instrument (the most advanced imaging system currently orbiting Mars) and modelled the flow of water down a slope. What the simulation showed was a surprise; the researchers went into the project thinking they were going to prove that the gullies were formed by water. Instead, they had shown that the shapes and characteristics of the observed gullies most resembled that of the modelled gullies shaped by dry debris tumbling down a slope.

The dry granular case was the winner. I was surprised. I started off thinking we were going to prove it’s liquid water.” – Jon D. Pelletier

Looking at the comparison between the two cases (water and dry debris flow) and the HiRISE observations, it is very easy to see the striking resemblance between dry debris flow and what is actually observed. The water simulation appears to be more diffuse, lacking the characteristic “fingers” reaching down the slope.

On hearing the news in 2006 that there was a possibility of liquid water flowing on the Martian surface, biologists hoped that a new tool had been found to pinpoint where sub-surface deposits of liquid water may be stored. This will have provided future missions with a location to hunt for life in the most likely place, near fresh gullies, near a source of water. Unfortunately it seems that these gullies are in fact shaped by small landslides, not by surges of water from a sub-surface reservoir.

Research to be published in the March issue of Geology, entitled: “Recent bright gully deposits on Mars: wet or dry flow?“.

Source: University of Arizona News

15 Responses

  1. Terragen says

    Just be cause we want to discover something, doesn’t make it true. Ah well, keep hunting, water diviners! Nothing is proved yet, but looks like we all got caught up in wishful thinking… again…

  2. Ben Shelef says

    The “hunt” for microbial life is not on the surface, but several feet underground, where we know there’s plenty of water. Even the most optimist of hunters don’t think that surface water can persist or can harbor life.

    If anything, such water is a shortcut to digging and looking for life in the underground water ice or any underground liquid water that can persist under that ice.

  3. tacitus says

    Terragen, there is nothing wrong with wishful thinking, as long as it doesn’t get the way of doing the science. I don’t believe anyone say their had proof of running water on the surface of Mars, it was just one theory that seemed to fit the initial evidence. There was always a good chance that once more research was done, we would find that it wasn’t water after all.

    The only people who look stupid now are cranks like Richard Hoagland who said the streaks confirmed that they were “right all along” in claiming that flowing water would be found on Mars.

  4. Valcanoman says

    tacitus: you might read the article a little more carefully, no one quoted Richard Hoagland in any of those reports or in the article. Only good solid scientific authors made the remarkable statments, water.

  5. Earl Towson says

    Why do the streaks disappear so rapidly? And why are they mostly found in the shodows of craters at high latituds?

  6. Astrophysician says

    However, Terragen has a point.

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

    Science needs to be objective – the hopes of scientists need to be bracketed before plunging into experiments. When scientists launch into studies and experiments looking for something specific, they run the chance of ruining it by finding things that aren’t really there.

  7. NeoGuru says

    Has anybody else noticed that the temperature on Mars is cold enough to freeze CO2? Water is a comfortable solid at those temperatures. What’choo talkin’ ’bout “water flowing on Mars”?

  8. Kevin Koski says

    Lets see what the Pnoenix tests arrive at for a conclusion, and what else the MRO will find,probaly just at the poles now in the form of water ice,should be an exciting time.

  9. Astrofiend says

    “NeoGuru Says:
    March 2nd, 2008 at 11:14 am

    Has anybody else noticed that the temperature on Mars is cold enough to freeze CO2? …”

    Yeah, but water has a very high specific heat capacity, which means that it can store a lot of heat energy. Hence, it would take a while for it to freeze solid if it was hot and then suddenly gushed out onto the surface.

    There are a few conceivable scenarios in which warm water could be located not too far from the surface and then expelled, but nobody knows how likely or not they may be. Hence the interest over this result.

  10. Alphonso Richardson says

    Oh well, keep looking, they may turn something up. Then again…………………..

  11. GBendt says

    The temperature on Mars as well as the atmospheric pressure are too low to allow any liquid water to exist on the martian surface.
    Nevertheless it seems that Mars does not care about our concepts of science. There is stuff flow ingat places and at conditions where we were taught that nothing can flow. Seems there are plenty of facts of which we do not have an idea yet. Within a couple of years from now, we will hopefully know a lot more.

    Every computer simulation is based on a set of formulas that are together meant to describe the behaviour of a system. If this description is incomplete because not all aspects of the system were available and considered properly, the simulation may yield an impressive result, but a wrong one.

    Many people hope that we may find liquid water on Mars. The idea of fresh water seeping from the slopes of a hill on a planet , makes such a planet to become something earthlike and inhabitable, something worth while to conquer. Such an idea is of some help if you struggle for more funds for the exploration of Mars.

    The result of these exploration may very well be that we will estimate our planet higher than ever. So let us explore that remote, cold dry, airless and most unpleasant place. It will help us.

    Not everything that is flowing on Mars must necessarily be water. Perhaps it might make you shiver and turn your inside out once you take a sip of it.



  12. Chuck Lam says

    Astrofriend’s reference to temperature is most likely correct. As everyone knows, water is liquid within a very narrow temperature range. It is true, however, that there may be a volcanic hot-spot that could maintain liquid water. Maybe an early snow-ball comet smacked into Mars near or onto one of the hot-spots. Scifi? Maybe not!

  13. Wigs says

    I know a couple of people I wouldn’t mind sending on a one way trip to Mars to see if there’s any water on it.

  14. Wigs says

    There’s no water on mars, never was.

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