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Darkened craters on Mars

Darkened craters on Elysium Planitia
Click for full image.

It’s time for the first cool image of 2020! The photo to the right, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 10, 2019. It shows a handful of darkened craters on the vast volcanic Elysium Planitia plain between the giant volcanoes Olympus Mons to the east and Elysium Mons to the north.

My first thought was that these dark craters were recent crater impacts, possibly a set of secondary impacts from a larger nearby impact. However, in looking at the archive of MRO’s high resolution camera at this location (Latitude 5.925° norther; Longitude 164.965°) I found that almost no high resolution images have been taken in this region, as shown by the overview map below to the right.

Overview map

The black cross indicates the location of the image above. The red rectangles indicate where MRO has taken other high resolution images. As you can see, this area, about a hundred square miles plus in size, is largely untouched by high resolution images. The nearest other image, to the south, also showed the same features, a generally featureless plain with a few scattered small craters, some of which are darkened in their interior.

That not all the craters are darkened strengthens the hypothesis that the darkened craters are recent impacts, all occurring at the same time. However, for an impact to have created so many secondaries suggests that it was relatively large, and though I could find some research that found recent impacts in this region (here, here, and here [pdf]), no impact seemed large or close enough to account for all these darkened craters.

Then again, maybe this area was not hit by one large impact with secondaries, but by a rubble pile asteroid like Bennu, that broke up upon entering the Martian atmosphere and splattered a scattering of rocks across a wide area. That could account for the many recent small impacts.

Or maybe wind is removing dust to reveal the darker basalt volcanic material below, as seen in the dark splotches on the lower western flanks of Olympus Mons. The problem with this theory is that it is difficult to explain why only some craters are attracting wind, and why the wind removal is only happening in craters. Some of the same theories that explain the Olympus Mons splotches might apply (these craters happened to be thermally warmer for any number of reasons, thereby attracting dust devils). Somehow this explanation does not promote enthusiasm.

So what do we have? We have another cool image, and another Martian geological mystery that likely cannot be solved until people are actually roaming about on the surface of Mars.


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.


  • Lee S

    Has anyone done any research on the effects of the Martian atmosphere on meteorites? I remember reading ( a long time ago!) Of the threat that micro meteorites pose to potential moon colonies, but I wonder if like Earth, Mars has enough atmosphere to burn up the majority of incoming space rocks?
    And regarding the theory of wind clearing the craters… Dust devils did a good job of clearing spirit and opportunities solar panels, so perhaps the same, localised effect is in play here?

  • I note that the large craters are clustered together improbably. Why might this be? Were the large craters the result of a single meteorite that had broken up?

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