A river valley floor on Mars


Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

 
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit.

 
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
 

"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs." --San Antonio Express-News

Overview of Reull Valles region

Today’s cool image focuses in on a Mars Reconnaissance Orbiter (MRO) uncaptioned photograph taken of the valley floor of Reull Vallis, a meandering canyon that drains into Hellas Basin, the bottom of Mars.

The image on the right is not that photograph. Instead, it is an overview of the area surrounding it. The image location is indicated by the black cross, dead center within the floor of Reull Vallis itself. This valley, as well as Dao and Niger to the northwest but lower in elevation are all thought to have been formed from flowing water, all of which apparently drained from the east and to the west into Hellas Basin.

This last detail is very important and bears repeating before looking at today’s subject image. The river that formed Reull Vallis flowed from the east to the west. Now for that picture.

The floor of Reull Valles
Click for full image.

The cropped image on the left, slightly reduced to post here, shows the middle section of the full photograph, but it is typical of the entire image. What we have is a complex pattern of sharp curving ridges with depressions meandering in all directions. There is absolutely no indication that a river once flowed across this surface from the east to the west. None.

Other images of Reull Vallis do show this flow pattern. At this location, however, where the valley floor appears to be particularly wide, that flow pattern vanishes and is replaced by this helter-skelter terrain, illustrating what the planetary geologists readily admit: “The morphology of Reull Vallis suggests it had a long and complex history, including subsurface and surface movement of fluids followed by extensive modification by mass wasting.”

Here we see that the floor has been significantly eroded by later processes after the water disappeared. Later, wind action, which probably contributed to that erosion, also placed dust and dunes within the depressions here.

A lot of time has passed since that river flowed through Reull Valles. Or to put it another way, Mars has generally been a very dry place for a very long time. It might have considerable water at its poles as well hidden in an underground ice aquifer, but its surface is far drier than any desert on Earth, and has been for eons.

Future settlers need to recognize this. It will determine everything they do to establish a life here.

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