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A Martian river of ice

Glacial flow on Mars?
Click for full image.

Cool image time! The photo to the right, rotated, cropped and reduced to post here, was taken on May 13, 2021 by the high resolution camea on Mars Reconnaissance Orbiter (MRO). It spans the entire 4.7 mile width of the southern hemisphere canyon dubbed Reull Vallis. The white arrow indicates the direction of the downhill grade

The scientists title this image “Lineated Valley Fill.” The vagueness of this title is because they have not yet confirmed that this lineated valley fill is a glacier flowing downhill to the west.

Nonetheless, the material filling this valley has all the features one expects glaciers to exhibit. Not only is the the lineation aligned with the flow, it varies across the width of the canyon as glaciers normally do. At the edge the parallel grooves are depressed, probably because they are torn apart by the canyon walls as the glacier flows past. In turn, at the center of the flow the grooves are thinner and more tightly packed, and appear less disturbed. Here, the flow is smooth, less bothered by surrounding features.

This pattern also suggests the merging of two flows somewhere upstream.

A glance at the spectacular Concordia glacier in the Himalayas near the world’s second highest mountain, K2, illustrates the similarity of this Martian feature to Earth glaciers.

Reull Vallis itself flows down to Hellas Basin, the deepest basin on Mars. As it meanders downhill along its 650 mile length it steadily gets wider and less distinct as it drops into Hellas. Along its entire length MRO has photographed numerous similar examples of this lineated fill, all suggesting that under a thin layer of debris is a thick glacier, slowerly carving this canyon out.

The overview map below illustrates these facts nicely, while further reinforcing these glacial conclusions.

Overview map

The small red rectangle in the center marks the location of today’s image. The two black crosses indicate earlier cool image posts (here and here), both of which exhibited similar glacial-like flow features.

In addition to the two other images mentioned above, I have highlighted many other glacial features in Reull Vallis. For example, an MRO image just to the west of this one and posted in October 2020 shows similar lineated features.

Do a search on Behind the Black for “Reull” and you will see plenty of cool images that say this canyon was carved by glaciers, not flowing water.

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. All editions can also be purchased direct from the ebook publisher, ebookit, in which case you don't support the big tech companies and the author gets 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.


  • Chris

    Are the distances between lineation (correct?) as expected with a 1/3 gravity planet?

  • There appear to be craters in the flow, or at least, circular formations. If it’s a glacier, the progress is ‘glacial’, even by that standard.

  • Blair K Ivey: It is presently believed that the glaciers on Mars are not active, at least in this region. With no additional material being placed at their upstream ends, they are not being pushed forward.

  • Geoman

    There is something on earth called a rock glacier. As a normal glacier begins to melt, slowly, talus accumulates on the top. This talus becomes thick enough to insulate the underlying glacier. They usually occur when the glacier has a very low flow velocity, which is confirmed by the craters we see. Also the craters, if small enough, might be carried along, since they are largely in rock, not the underlying ice.

    Under the rock it is likely a mix of rock and ice, having more ice toward the bottom. These features could be tens of thousands of years old. On Mars, maybe millions of years.


  • Geoman

    I forgot to add – the beauty of glaciers is they preserve a tremendous amount of information on climate. Imagine what an rock glacier ice core from mars could tell us!

    1) Whether life exists or existed.
    2) Climatic cycles on mars. Do they match up with the Earth? During what period?
    3) A record of volcanic activity.
    5) A record of major impact events.
    6) Captured historic samples of the atmosphere.
    7) Past air temps.
    8) ????? something new and different.

  • Geoman: I think you are new here. If so, so a search on Behind the Black for “glaciers.” If you think this image is amazing you might find the wealth of other glacial data on Mars to be of interest.

  • Robert:

    Even if no new material is introduced upstream, I would think the weight of material would flatten the glacier, so that it resembled an alluvial plain in the valley. But at 0.3g, maybe these things take time.

  • Alex Andrite

    ” …. A glance at the spectacular Concordia glacier in the Himalayas … ”

    Wow, I followed that link to my great surprise.
    That is some spectacular geography !!
    Great photos.

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