A River Ran Through It: Why Do They Think There Was Once Water on Mars?

Why is everyone so excited about these dusty Mars rocks?

This week’s big news was the announcement of evidence for flowing water on Mars, based on images of what appear to be smooth river rock-type pebbles found by Curiosity. Of course that’s a big statement to make, and for good reason — identifying water, whether present or past, is one step closer to determining whether Mars was ever a suitable place for life to develop. Yet here we are, not even two months into the mission and Curiosity is already sending us solid clues that Mars was once a much wetter place than it is now.

JPL released a video today providing a brief-but-informative overview of what Curiosity has discovered in Gale Crater and why it’s gotten everyone so excited.

Check it out so you’ll have something to talk about over the weekend:

MSL Long Term Planner Sanjeev Gupta reviews Curiosity’s latest discovery

Video: JPLNews. Images: NASA/JPL-Caltech

9 Replies to “A River Ran Through It: Why Do They Think There Was Once Water on Mars?”

  1. For this to have been a river it means there had to be enough water vapor in the atmosphere for reasonable amount of rain. The mountain then could drive winds upwards, cooling the atmosphere and causing precipitation.


  2. This presents a nice mystery. Is the alluvial fan geologically old or recent?

    The central mound in Gale crater, and other more or less backfilled craters, predicts aeolian deposition and removal. The recent snowmelt theory predicts mound layered sedimentation, but I don’t think it is necessary for the backfill hypothesis.

    – The alluvial fan could be old, from before the backfill. The aeolian removal process would have slowed considerably when it hit more resistant streambed deposits.

    In this case the atmosphere would have been dense, and the water source and stream behavior could have been reminding of Earth conditions.

    – The alluvial fan could be recent, from after the removal.

    In this case the atmosphere would have been low pressure, and the water source would have been snowmelts. The 10 km long stream could well have wandered as shown in the video and deposited stream material where Curiosity found it.

    In the second pathway we would not expect to find much of organics. In the first pathway however, the stream persistence estimated to be thousands of years would have been time enough for any extant microbes to form so called desert varnish on any standing rocks nearby.

    I do hope they find a rock outcrop that they can sample with the SAM at Glenelg. It could be most auspicious.

    1. Big Bang Theory season premier this week was outstanding, Hope you were able to see it. Howard in space and wishing he could just stay there while his mother and Bernadette fight.

    2. I remember when the first rover landed on Mars back in 1996 where the images showed what clearly looked like flow lines around rocks. The area looked just as if flood water had been flowing the other day. Even back then it was very clear that liquid water had been flowing on Mars. The fact that even flow features on the scale of centimeters to meters were apparent raised this question. It is one thing to have large scale flow features persist for a couple of billion years on a .01 Torr atmospheric pressure. It seemed a bit odd to have such small scale features exist that long.


      1. I’m still unconvinced that the ‘flow lines’ you mention are caused by water. Instead I think we have vastly underestimated the wind’s capacity to transport materials in the 1/3 G on the Martian surface. Dust particulates on Mars appear to be extremely fine. When held in suspension due to atmospheric and surface heating, tribo electric currents generated in the direct impact solar wind, then you have what for all practical purposes are solids acting like liquids – liquifaction -.and therein ingredients for erosion.

      2. That could be, which would conform to an ancient theory of water flow. I think it is not likely that water has flowed on Mars for probably 2 or 3 billion years.


      3. I prefer horses before zebras when I hear hoof beats.

        Which makes me think LC is correct in that the ancient stream hypothesis is more likely. The finds are made on the older surface of the two southern ones (three surfaces comes together at Glenelg nearby) and it is at first view as heavily cratered as the rest of the crater floor.

        Still, I prefer to leave the dating to the Curiosity geologists.

  3. I think we’re seeing evidence of a whole new kind of weathering. One where dirt and dust particles act like a liquid when held in suspension. All of the info I’ve seen claim that particles of the size seen could not have been transported by wind… ON EARTH. But on Mars?

    We really don’t have a lot of experience with materials behavior in 1/3g, low pressure environments…

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