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On the rim of Mars’ Grand Canyon

The rim of Valles Marineris
Click for full image.

Cool image time! Mars has many grand geological features that will surely attract tourists in the far future, when the planet has been successfully colonized and humans live there with the same ease that we today live in what was the New World wilderness several hundred years ago.

Of those features, none probably compare with Valles Marineris, the largest known canyon in the solar system. When compared to it, the Grand Canyon — at about a mile deep, about ten miles wide, and about 280 miles long — is a mere pothole, hardly noticeable. Valles Marineris averages a depth of five miles, a width of 370 miles, and a length of 1,900 miles. You could fit many Grand Canyons within it.

The photo to the right, cropped to post here, was taken on July 13, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows only a tiny section of this gigantic canyon’s rim. At this spot the depth from rim to floor is about 4.3 miles, or about 22,700 feet. In the image itself I estimate the cliff at the rim to be somewhere between 6,000 to 8,000 feet high, more than the depth of the entire Grand Canyon. And that’s only this top cliff.

The three overview maps below show the context of this location within Valles Marineris.

Wide view of all of Valles Marineris

Wide view of this region of Valles Marineris

Close overview of the rim

The top overview map provides a view of Valles Marineris in its entirety, with the location of today’s image indicated by the white cross. The middle overview map zooms in on this particular part of Valles Marineris. The canyon in general is so large its interior canyons and mountains have their own names. At this point, the canyon’s width from the north rim to the narrow peninsula to the south is about 120 miles. Since Eos Chasma has a length of about 300 miles, the entire Grand Canyon could fit into it, with lots of room to spare.

The white rectangle with the small white box within it shows the area covered by the bottom overview map, with the image above indicated by the red box.

For the planetary scientists, this image is of interest because of the layers visible in that cliff wall. Even at this resolution, about 10 inches per pixel, at least two dark bands can be seen in the west-facing cliff, with several thinner bands hinted at.

It is believed [pdf] that the dark layers are lava flows, with the lighter layers between ash deposits, all built up by different volcanic events over time. Though scientists have not yet completed a full map of these layers, the first rough geological work estimates numerous eruption events and lava flows, covering more than a billion years, from about 3 to 4 billion years ago.

None of these conclusions however are certain. For example, while there is more certainty that the dark layers are hardened lava, the lighter and weaker layers between might not be volcanic ash. There is not enough good data yet to be certain.

If true however they suggest that Mars had volcanic eruptions of a size and extent that dwarf anything found on Earth. Nor should we be surprised, considering that just to the west of this humongous canyon are Mars’ largest volcanoes, also the biggest in the solar system.

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 available at Amazon, Barnes & Noble, and all book vendors. The ebook can 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. Note that the price for the ebook, $3.99, goes up to $5.99 on September 1, 2022.


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


  • Carl

    Incredible. In the thin, low H2O atmosphere, the view would be even more amazing.

    Too bad no limestone in those cliffs!

  • Alex Andrite

    Ah … a long way from Saturday morning cartoons ….

  • Robert17

    I suggest that due to the depth of the canyon, the atmospheric pressure is enough to maintain a higher temperature such as is found on Earth where the surface is lower than sea level, think Dead Sea as an example. Boyle’s Law. If this is the case there would be a greater likelihood of liquid water at the surface during some seasons if H2O is present in the canyon. Therefore a greater likelihood of finding some type of life form. To me the hurdles of navigating this type of terrain safely and successfully would be difficult but worthwhile.

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