Click for full image.
Cool image time! The photo to the right, cropped and reduced to post here, was taken on June 5, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a ridgeline at the base of the giant volcano Pavonis Mons, with slope streaks on ridge’s north and south sides.
Slope streaks are a mysterious phenomenon unique to Mars. While they resemble an avalanche, they do not change the topography of the surface at all. They appear to occur randomly year round, fading slowly with time. Also, while most are dark, scientists have also spotted bright slope streaks as well.
Slope streaks also only appear on surfaces covered with a layer of fine dust, something that is obviously the case in the cool image to the right. There is so much dust on the surface here that bedrock only appears at the top of the ridge, peeking out in only a few places.
The location of this image, as shown in the overview map below, adds some additional details.
Pavonis Mons is the central volcano of the three that sit between the giant canyon Valles Marineris to the east and Mars’ biggest volcano, Olympus Mons, to the west. The white rectangle marks the location of this photo, at the very base of Pavonis.
Thus, under the fine dust layers that allowed the formation of these slope streaks it is likely that all the rock is volcanic in nature, part of the vast lava flows that came down this volcano more than a billion years ago.
Why there is a ridge here is a little unclear. It appears that as the lava flowed downhill, it might have pushed debris in front of it, which piled up to form this higher ridge. (That is a pure uneducated guess, however.) Later, the dust piled up on the surface, allowing for slope streaks to appear periodically, likely instigated by a small rock fall at the top.
As for the streaks, the process that forms them remains unknown. Several theories have been proposed (dust flows, brine flows) but none really fits all the facts. They remain one of Mars’ many geological mysteries.
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.
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.