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.

Scientists propose new theory to explain mysterious slope streaks on Mars

Slope streaks on Mars
Click for full image.

In a paper published earlier this month, scientists have proposed a new theory to explain the the origin of slope streaks on Mars, a unique Martian geological feature that at first glance look like a stainlike avalanches which also appear to do nothing to change the surface topography. (See earlier posts here and here for a description of this strange Martian phenomenon.)

Essentially, data from the orbiters suggests that carbon dioxide frost develops just under the surface during the night. In equatorial regions this frost mixes with dust (allowing it to exist even in these warmer climates). When the morning light hits the frost it causes it to sublimate away, which in turn causes the appearance of slope streaks as the dust is released from the frost.

From the paper’s abstract:

At sunrise, sublimation-driven winds within the regolith are occasionally strong enough to displace individual dust grains, initiating and sustaining dust avalanches on steep slopes, forming ground features known as slope streaks. This model suggests that the CO2 frost cycle is an active geomorphological agent at all latitudes and not just at high or polar latitudes, and possibly a key factor maintaining mobile dust reservoirs at the surface.

The cool image above, cropped and reduced to post here, was taken on October 28, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and shows an excellent example of two very spectacular large slope streaks, one long and narrow and another short and wide. Located at 23 degrees, this is an area where no ice has yet been found near the surface.

This new theory joins two other popular theories attempting to explain slope streaks. The others postulate that the streaks are either dust avalanches of a different type or the percolation of a brine of chloride and/or perchlorate in a thin layer several inches thick close to the surface.

None have been proven. None likely fit all the known data at this point.


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  • Greg the Geologist

    Does appear to modify topography in a small way. Look at the previous streak tracks on either side of the long active streak – note how they swerve in response to hills in the pathway. So there’s clearly a deposit there, even if a thin one. And, near the center, notice the streak tracks in the same area as elongate ‘S’-shaped dunes (I think they’re dunes). Would be interesting to work out relative ages of streaks and dunes using classic geological principles. A lot going on in this image!

  • Further up the image is the same phenomenon, also exhibiting flow around features. The flows seem to be partially filled-in, and there looks to be flow deposits at the base of the hill. Possible dunes adjacent?

    I am curious about the dunes (?) in the featured image. Why that particular pattern? I am thinking that the surface of Mars is more ‘plastic’ than we have experience with.

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