Curiosity spies gravel, proving existence of ancient stream bed on Mars

Curiosity spies gravel, proving existence of ancient stream bed on Mars

Summary: The Mars rover has made its first significant finding, providing geological evidence of a water stream flowing, once upon a time, on the Red Planet.

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TOPICS: Nasa / Space
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The Curiosity Mars rover has made its first major discovery: solid geological evidence of an ancient water stream on the surface of the Red Planet.

We have had suggestions of old river beds on Mars since the early Seventies, thanks to images from the Mariner 9 mission, and we also know that Mars has ice at its poles and a small amount of water vapour in its atmosphere. However, Curiosity has now provided conclusive evidence of a fast-flowing and lengthy stream at some point in the past.

Mars ancient riverbed
The 'Hottah' outcrop surveyed by Curiosity. Scientists believe it to be an ancient riverbed. (Image credit: NASA)

The evidence comes from gravels surveyed by the rover. The gravels are cemented together in a conglomerate that now looks like a rocky outcrop. The scientists believe it looks that way due to being hit by a meteorite, long after it dried up.

According to the Planetary Science Institute (PSI) in Arizona, the rocks vary in size from grains of sand to golf-ball-sized pebbles and, crucially, some are rounded.

"The shapes tell you they were transported and the sizes tell you they couldn't be transported by wind," PSI senior scientist Rebecca Williams, a co-investigator on the Curiosity mission, said in a statement. "They were transported by water flow."

Williams added that the discovery would help scientists work out the amount of water that flowed at the site — right now, they reckon it moved at just under a metre a second and was between ankle- and hip-deep — and for how long it flowed.

Ultimately, this will aid their quest to figure out which bits of Mars might have once been habitable.

Topic: Nasa / Space

David Meyer

About David Meyer

David Meyer is a freelance technology journalist. He fell into journalism when he realised his musical career wouldn't pay the bills. David's main focus is on communications, as well as internet technologies, regulation and mobile devices.

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  • Curiosity spies gravel, proving existence of ancient stream bed on Mars

    "The shapes tell you they were transported and the sizes tell you they couldn't be transported by wind,"

    Is this enough to conclude that the flow was water? Why not some other liquid? What gases are present in the atmosphere - is Oxygen one of the gases?

    It would appear that this conclusion is hasty, except if there is other evidence apart from what was stated.
    ckharry@...
    • Re: Why not some other liquid?

      What else would be liquid at likely temperatures in Mars' past?
      ldo17
    • Planetary Geology

      I took a class in planetary geology in my freshman year. So I know from that experience that though their math is sloppy, planetary geologists do have a pretty good idea what they are talking about: they know the physics quite well enough.

      So if they way it had to be transported by water, odds are they are right. They certainly did not forget to account for possible changes in temperature and atmospheric composition over the millennia. They know, for example, that in the past, the atmosphere could have been thicker (certain if you go back far enough), and could have contained the oxygen that is now mostly in the crust.

      As for other fluids, even today, it is not cold enough for liquid ammonia. Nor is there that much nitrogen.

      BTW: we already have pretty solid evidence of PAST existence of water in the phyllosilicate rocks found back in 2006.
      mejohnsn
      • I'd be looking for hydrate minerals

        I'm guessing that their presence at the surface would be proof, since they certainly don't come out of volcanoes.
        John L. Ries
        • Carbonates would also be a good indicator

          AFAIK, the only chemical processes that produce carbonate involve water. Furthermore, most carbonates are decomposed by heat (the only exceptions I'm aware of are those of alkali metals like sodium and potassium), which means they don't occur in igneous rocks.
          John L. Ries
  • Of course they could be transported by wind

    if your atmosphere was thick enough or your wind high enough. But, we're looking for water, by thunder, and we're going to find evidence of water no matter how much we have to twist and strain.
    baggins_z
    • Re: of course...

      Of course NOT. There is no evidence the atmosphere on Mars was ever THAT thick. Not even on Earth do we get rocks that weight transported by wind.
      mejohnsn
      • The big rocks

        are conglomerate rocks of fused pebbles. The pebbles themselves are only a few centimeters across. Look at the scale on the image. These are not boulders or even rocks. They are pebbles.
        baggins_z
        • Oh, and the scientists already admit

          that a meteor has come along and blown everything up in the area, but somehow the water-polished rocks are completely unaffected. This is typical modern science at work. Take a possible explanation and present it as uncontested truth because it fits the paradigm.
          baggins_z
  • Mars

    I agree with mejohnsn.
    rmctwo@...
  • Wind travel not possible!?

    "The shapes tell you they were transported and the sizes tell you they couldn't be transported by wind,"

    The larger gravel was only golf ball sized. Winds speeds measured by Viking in the 1970's were measured as high as 60mph. I realize rock is more dense, and the surface more uneven, but I've seen my golf ball moved on greens by wind in the 30mph range. I would imagine golf ball sized rocks could indeed be transported by strong enough wind. Also Mars, like earth, has prevailing winds, so it it seems conceivable high winds could have an effect here. This is the problem when scientists want to find something (i.e. water); they can easily draw facts based on the conclusion.
    dadxfour
    • Atmosphere on Marse is about 1/10 that of earch.

      To get a corresponding effect of 30mph on earth you would need between 200 and 300 mph on Mars. Current measures of wind speed there are less than half that.
      jessepollard
    • Rocks! not golf balls ffs

      You cannot compare an experience involving a very smooth, near-spherical object (which has been manufactured, at least in part, to roll as easily as possible moving along a surface which is cultivated carefully in order to reduce friction) to similarly-sized but randomly-irregular pebbles moving along a rough and irregular surface in order to discredit scientists in general. Go try and putt a couple small rocks down a gravel driveway and see the difference these factors make. Go back to playing golf and try not to hurt yourself.
      theJof
  • Big Bang Theory - Who Needs it?

    Who needs to watch Big Bang Theory when you have these conversations? I feel like I am fully integrated and have no clue what is being said. Thanks, this is a blast.
    tomtazz