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Seasonal avalanches in Martian dune gully

Seasonal changes in Martian dune gully
Click for full image.

The science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) today released a very cool pair of images, taken a Martian year apart, showing some significant changes that had occurred during that time in a large sand dune slope inside a crater. On the right is that pair, reduced and with the top image slightly lightened to bring out the features. As they wrote in the caption,

One large gully in particular has had major changes in every Martian winter since [MRO’s high resolution camera] began monitoring, triggered by the seasonal dry ice frost that accumulates each year.

This time there was an especially large change, depositing a huge mass of sand. The sand divided into many small toes near its end, or perhaps many individual flows descended near the same spot. Additionally, a long sinuous ridge of sand was deposited. This could be a “levee” that formed along one side of a flow, but there is not much sand past the end of the ridge, so it might also be the main body of a flow.

Nor is this dune gully the only active one in this crater, dubbed Matara Crater, located in the southern cratered highlands at about 50 degrees south latitude. If you look at the full image and compare it with an image from 2009 there are many changes across the entire slope field that extends a considerable distance to the north and south of the cropped section shown above.

At this latitude atmospheric carbon dioxide settles as frost during the winter, then sublimates away with the coming of spring. The freeze-sublimation process disturbs the sand each year, causing these avalanches.

Conscious Choice cover

Now available in hardback and paperback as well as ebook!


From the press release: In this ground-breaking new history of early America, historian Robert Zimmerman not only exposes the lie behind The New York Times 1619 Project that falsely claims slavery is central to the history of the United States, he also provides profound lessons about the nature of human societies, lessons important for Americans today as well as for all future settlers on Mars and elsewhere in space.

Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space, is a riveting page-turning story that documents how slavery slowly became pervasive in the southern British colonies of North America, colonies founded by a people and culture that not only did not allow slavery but in every way were hostile to the practice.  
Conscious Choice does more however. In telling the tragic history of the Virginia colony and the rise of slavery there, Zimmerman lays out the proper path for creating healthy societies in places like the Moon and Mars.


“Zimmerman’s ground-breaking history provides every future generation the basic framework for establishing new societies on other worlds. We would be wise to heed what he says.” —Robert Zubrin, founder of founder of the Mars Society.


All editions are available at Amazon, Barnes & Noble, and all book vendors, with the ebook priced at $5.99 before discount. The ebook can also be purchased direct from my ebook publisher, ebookit, in which case you don't support the big tech companies and I get a bigger cut much sooner.


Autographed printed copies are also available at discount directly from me (hardback $24.95; paperback $14.95; Shipping cost for either: $5.00). Just email me at zimmerman @ nasw dot org.


  • sippin_bourbon

    These posts do not get as many comments, but I do enjoy them immensely.

    I feel I should comment so you know they are appreciated.

    Also, came across this yesterday:

    As an amateur astronomer, I have advocated for a far side observatory myself, I think
    this is great. I have not found a whole lot about this project just yet.

    I also advocate for a standard spectrum scope on the far side as well.

  • sippin_bourbon: Thank you for the kind words. I do wonder at times if anyone is actually reading my science posts. It seems from the comments the only thing people these days really care about is politics. Though very very important, life should never be all politics. When it is, things are not good.

    A radio telescope on the far side of the Moon makes great sense. This research however is very much in the powerpoint stage. We need to be able to get there, reliably, at low cost, before I will take it very seriously.

  • Ian C.

    I do wonder at times if anyone is actually reading my science posts.

    Definitely. But it’s often hard for me to ask or add something of substance when it comes to geological aspects.

  • Ian C: As I used to tell my film students when I was teaching film in New York back in the early 1990s, the only stupid question is the one you don’t ask. Feel free to speculate and ask! In truth, as I say repeatedly, your guess is often as good as mine. And mine are sometimes (rarely) as good as the planetary geologists who do this for a living.

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