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On February 5, 2023 I will celebrate my 70th birthday. Yay! As I do every year during this birthday month, I run a campaign to raise money to support my work here at Behind The Black. I do not run ads. My only support comes from my readers, which leaves me utterly free to speak my mind openly about space, culture, and politics. Please consider supporting me in this work by giving either a one-time contribution or a regular subscription, in any one of the following ways:


1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.


2. Donate through Gabpay, using my email address zimmerman @ nasw dot org.

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The eroding edge of Mars’ largest volcanic ash field

Eroding yardangs at the edge of Mars' largest volcanic ash field
Click for full image.

Cool image time! In the regions between the biggest volcanoes on Mars is the Medusae Fossae Formation, a immense deposit of volcanic ash that extends across as much surface area as the nation of India. As planetary scientist Kevin Lewis of Johns Hopkins University explained to me previously,

In general, much of the [formation] seems to be in net erosion now, retaining very few craters on the surface. …One hypothesis is that this long term erosion, since it’s so enormous, is the primary source of the dust we see covering the much of the planet’s surface.

The image above, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on January 25, 2020. It shows one very small area at the very edge of the Medusae ash deposit, in a region where that deposit is clearly being eroding away by the prevailing southeast-to-northwest winds. The mesas of this ash that remain are called yardangs, their ash more tightly pressed together so that it resists erosion a bit longer than the surrounding material.

In the context map below the location of these yardangs is indicated by the white cross, right on the edge of the Medusae ash field.

Overview map

Inset showing exposed ash layers

Other images taken by MRO along this edge, such as this one, show variations of the same type of erosion, though not as dramatic in scale or extent. A second high resolution MRO photo taken just to the north of the image above shows that this wind-blown mesa terrain continues for at least one to two miles northward.

To the right is a zoomed in close-up of the area in the white box. It shows why this image was dubbed “Exposed Layers in Medusae Fossae Formation.” The volcanic ash deposits apparently were not the result of one, or even ten volcanic eruptions, but many over a long period of time, each placing a new layer down that the wind is now exposing as it erodes the ash away.

That this vast ash deposit is made of many layers from many volcanic eruptions should not surprise us. The region is surrounded by gigantic volcanoes, the largest in the solar system. When they were active and growing, there must have been many violent repeated eruptions, spewing ash over large distances. The Medusae Fossae Formation is the remains of that volcanic era, now thought to have ended one to two billion years ago.

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.

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