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A chain of Martian sinkholes

Chain of sinkholes on Mars
Click for full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on June 17, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a somewhat straight depression with several wider and deeper pits along it.

The feature immediately suggests sinkholes that exist because the ground is sagging into voids below ground. Yet, both the straight and circular depressions also appear filled, showing no evidence that they connect to any below ground cavities.

Are the sinks the result of a fissure produced by a graben, when two large blocks shift relative to each other to cause a fissure to appear? Or are they evidence of an underground lava tube? Or maybe they are the filled remains of a now mostly buried canyon carved by water or ice?

As always, a wider view helps clarify things, though whether it answers the question is uncertain.

Overview map

Mosaic of two MRO context camera photos
To see full images, go here and here.

The overview map to the right, with the photo’s location indicated by the white rectangle, shows that this depression is located in the Tharsis Bulge, the region on Mars where its largest volcanoes are found. To the southeast is Ascraeus Mons, Mars second largest volcano, about 600 miles away. To the west about 1,900 miles away is Olympus Mons, Mars’ largest.

Thus, the feature is not likely a flow feature carved by water or ice. The altitude is too high, almost all the geological features here are volcanic, and the latitude, 17 degrees north, is in the Martian dry equatorial regions where little evidence of surface water or ice is found.

The second image to the right, created by me from two MRO context camera images, shows a wider view of this region. The black rectangular marks the area covered by the photo above.

As you can see, there are two pit chains in this area. They are parallel to each other but also appear have formed separately. Based on the lobate flow to the northwest that resembles very much frozen lava, both chains run in a direction that seems at right angles to the downhill grade.

Based on the wider images and the location, my guess therefore is that these depressions signal a graben, fissures created along a fault. The sinks suggest that the fissures are not entirely filled, but have some voids below in which the surface dust and debris is sinking.

What is most puzzling about these features is their isolation. If formed from faults, you would expect the faults to be more extensive. Instead, the two cracks are relatively small features on a smooth flat lava plain.

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.

One comment

  • Greg the Geologist

    Cool and very curious for sure! Another puzzling aspect is the clear wind-driven dunes in the depressions (maybe graben), and the streaks on the mesa just south of the linear depression, indicating wind generally west-to-east. Then on the surrounding mesa, the only features that appear wind-shaped are the many very small linear structures oriented north-northeast. Not sure what they could be.

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