Jan 12 2014

Postcards from Mars

Smithsonian Magazine offers snapshots taken by Spirit and Opportunity over the past ten years.

Another bow to the engineers. They figured the two Rovers would last three months. Spirit lasted six years and Opportunity is still working, a decade in.

Check out the rounded rocks. A long-gone river?

A closeup of tiny spherical rocks clustered in a square inch of the Martian surface, captured by Opportunity. Full size version. (NASA/JPL-Caltech/Cornell/USGS/Cathy Weitz)



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  1. 1

    Could sand blasting from Mars’ known high winds have produced the roundness?

  2. 2
    Al Dente

    Opportunity is still working, a decade in.

    I am impressed.

  3. 3
    Ophelia Benson

    I’ve been wondering that, about sand & wind. But someone who talked about a different photo of rounded rocks, this one sent by Curiosity, emphasized that the rounding is characteristic of rushing water as opposed to anything else. Naturally I have no idea, personally, how reliable that is…but he said it as part of a case for thinking there had been a large and fast-flowing river there in the past.

    I wonder if sand-blasted rocks are more pitted…

  4. 4
    Ophelia Benson

    Is there a geologist in the house?!

  5. 5

    There is Dana Hunter, just off the mainpage from you. Give her a bell.

    What has really interested me is the sand. There are cracks in it and you can see steep sides where either the sand has shrunk away from some pebbles or the pebbles have been pushed into the sand. That doesn’t happen in dry sand.

  6. 6

    The one that really gets me is the fourth image.

    It looks for all the world like pebble imbedded, calcium rich sedimentary rock, the sort that forms under water.

  7. 7

    They’re beautiful. I would also recommend contacting Dana Hunter regarding the water/wind question.

    I’m just… That’s a whole different world in those photos. A different planet. That is mind-numbingly amazingly astounding. Wow.

  8. 8
    Ophelia Benson

    I askt Dana.

    I know, isn’t it? So, so amazing. Lucky us to be alive for it.

  9. 9
    Dave Ricks

    @5 badweasel, your observation about the gaps around the pebbles made me remember how a river current can scour sediment from bridge pilings on the upstream side, and that led me to this story about Martian wind making rocks and pebbles walk into the wind. Funny how that story is in the realm of classical physics, but counterintuitive and only known in the last 5 years.

    The drawing on this page about the same story might explain gaps around pebbles. My first thought was the gaps were from scouring on the upwind side, but after seeing the drawing, I think the gaps are from deposition on the downwind side (and changing wind direction might make the gaps go all around).

  10. 10
    Ophelia Benson

    Wo, interesting.

  11. 11

    @9 Dave. Thanks for your reply. It is an suggestion for the picture shown above but I am not convinced it is wind that is causing the gaps between taround the pebbles. For one the gaps are narrow and fringed with a sharp edge. I would have though that wind would have eroded a wider, smoother depression in the sand around the pebbles. The second thing is that such gaps appear only around a few of the embedded pebbles.

    Push a pebble into wet sand and what you get is something very similar. My pet theory is that Opportunity has run over those pebbles. But its the apparent ‘wetness’ of the sand that is far more interesting.

  12. 12
    Bernard Hurley

    Erosion of small rocks or pebbles by water tends to by symmetrical because they get bounced about a lot. Erosion from particles in fast moving gasses tends to be more asymmetrical because the objects get bounced around less. However they do get bounced around so to be absolutely sure it would be necessary to investigate the precise conditions under which these pebbles were formed. But it does look like water erosion to me, not that I’m an expert of any kind.

  13. 13

    These are amazing. I especially admire the sunset. People comment on how familiar it is, but is it really? No deep blues or purples, No deep reds or oranges. It looks cold to me, desolate. For many good reasons though I suppose. I’d love to see some microscopic shots of the sand itself.

  14. 14
    StevoR : Free West Papua, free Tibet, let the Chagossians return!

    For those who haven’t seen it yet this Youtube clip – ‘Good Old Girls’ by shammond42 music by Marian Call :


    is a wonderful poignant tribute to the Mars Exploration Rovers Spirit & Opportunity. Opportunity still roams the rusted sands of Mars.

  15. 15
    Dana Hunter

    Still trying to track down this photo – the article provides no link to where it came from and I’ve had no luck spelunking NASA. It says in the article that we’re looking at an inch of space – that means these rocks are itty-bitty. So this probably isn’t a river. Without finding the source for this photo so I can find out more about the location, I can’t say what we’re looking at.

    But I can tell you, water flowed on Mars. I’ve got ten million topics in queue right now, but I’ve downloaded a bunch o’ recent papers, and I’ll have something written up by summer. Probably.

    For anyone who’s impatient, you can see the press release here and there’s a nice write-up by geologist Wayne Ranney here.

  16. 16
    Ophelia Benson

    Cool, Dana, thanks. It even says right in the caption that it’s an inch of space, but I didn’t realize that translated to probably not a river. (Is that because rocks that small would be eroded out of existence in a river?)

  17. 17
    Dana Hunter

    You’re welcome! It’s a fun little investigation and reminds me I was gonna do up some Mars geology someday. No time like the present to get crack-a-lackin.

    ” Is that because rocks that small would be eroded out of existence in a river?”

    Sorta, but my first thought was, at that scale, mini-things sometimes eerily resemble big things without being at all related. Also it now occurs to me that at that scale what looks like sand is probably finer than what geologists consider sand, so it’s not. We’re not looking at the result of a recently-running stream, therefore.

    I’d narrowed the search down last night to the region of Mars I thought the photo *may* have come from, the Meridiani Plains. But I couldn’t find the actual image, so I tweeted the author of the piece to see if he had the link to the source image. And he did! And I’d actually nailed the broad geographical location! *Happy dance* I downloaded a crap-ton of papers on that area and Mars geo in general last night, so I’ll have something nice and thorough soonish. In the meantime, this is the link to the photo , with the caption explaining what it is. This is what our “rocks” are. So neat!

    Thanks for the inspiration!

  18. 18
    Ophelia Benson

    Cool! Isn’t it amazing having instant access to the authors of things? I’m still not jaded about it.

    Dana’s post is posted, y’all:


  1. 19
    In Which I Find the Solution to a Martian Geomystery » En Tequila Es Verdad

    […] yeah, what Ophelia said: “So, so amazing. Lucky us to be alive for […]

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