Conscious Choice cover

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.

 

Available everywhere for $3.99 (before discount) at Amazon, Barnes & Noble, and all ebook vendors, or direct from the ebook publisher, ebookit. And if you buy it from ebookit you don't support the big tech companies and I get a bigger cut much sooner.


Isidis Basin, on whose margin Perseverance will roam

Pedestal craters in Isidis Basin
Click for full image.

Overview map

Today’s cool image to the right, cropped and reduced to post here, highlights the floor of one of Mars’ largest basins, dubbed Isidis Planitia, and located at the transition zone between the planet’s northern lowland plains and the southern cratered highlands.

The overview map below of Isidis Basin provides some context. The white box shows where this particular image is located. Jezero Crater, indicated by the red circle (which is also about the size of the crater), is where the rover Perseverance is going to land and roam come February 2021, should all go well. For scale, Isidis is about the size of the eastern half of the United States. If Chicago was located at Jezero Crater, Baltimore would be on the basin’s eastern edge, at around 4 o’clock.

This particular section of the full photo, taken on April 5, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), shows many features very typical of the floor of Isidis Basin, which also immediately reveal a great deal about its possible history.

In this small snippet we can see what at first glance appear to be pedestal craters standing up like mesas, with ordinary craters scattered about on that lower surrounding terrain. Clearly, if these are pedestal craters they had to have been created first, and then over a very long time erosion processes ate away at that plain, leaving these pedestals (which had become resistant to erosion because the impact had packed their material together and made it harder) behind as mesas.

Then, after this period of erosion was complete enough additional time was required for at least one or two rounds of cratering to occur, leaving behind the many more younger craters on the plain floor, many of which are now partly buried by dust and sand.

The problem is that these mesas are almost certainly not pedestal craters, despite their appearance. Most such craters are found at much higher latitudes, above 30 degrees latitude. Instead, scientists believe that these are cones formed by volcanic processes, not impact.

Isidis is thought to have been created around 4 billion years ago by an large impact [pdf]. Since then volcanic processes followed by the long slow erosion caused by the wind of Mars’ thin atmosphere as well as the planet’s cyclical and changing climate have sculptured its floor.

The cones are thought to have formed during that volcanic period in the basin’s first billion years. Some scientists think the process that produced them was purely volcanic, others think that water ice might have also been involved. The latter theory has a problem in that it requires an ice sheet at the low equatorial latitudes of Isidis. Though this is not impossible, considering the wide swings in the planet’s rotational tilt that is thought to cause large cyclical climate changes, it has been difficult so far to come up with any scenario that makes it possible.

At this point no theory is strongly favored. The data is simply too inconclusive. We really don’t know what happened here precisely, and likely won’t know until we can put footprints on the ground and get a better understanding of Mars’ entire geological and climate history.

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3 comments

  • Greg the Geologist

    The light-toned linear ‘streaks’ surrounding the craters have a unique appearance. Thought they might represent fracturing, but looking at what appear to be dunes in the 2 craters in the lower left, and the generally common orientation, I’d call them thin ‘linear’ (properly longitudinal or seif) dunes. Cool features!

  • Greg the Geologist: Gee, I hadn’t even noticed those linear dunes. Tells us something about the prevailing winds here. Thanks!

  • Star Bird

    Mars has Craters lots of Craters it looks like Marvin a has not prefected his Eludium Q-36 Explosive Space Modulator yet

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