January 9, 2025 | David F. Coppedge

ENST: Living Murals

What causes “desert varnish”
on canyon walls? The answer
is lively and surprising

 

This article by CEH editor David Coppedge was published at Evolution News on July 16, 2021.


Living Murals: Wall Art Made by Photosynthetic Bacteria
by David Coppedge, Evolution News and Science Today
July 16, 2021

Familiar to every desert explorer, certain dark shiny walls stand out from the normally red cliffs of mesas and canyons in the southwestern United States. Native Americans for centuries etched drawings into them. The ubiquitous desert varnish that coats sunlit walls of sandstone in Utah and other desert environments around the world, though, has long been an enigma to scientists. How does it form? Why does it form? Now, they believe they have the answer: the artists are photosynthetic bacteria.

In their commentary in PNAS, “Shining light on photosynthetic microbes and manganese-enriched rock varnish,” Valeria C. Culotta and Asia S. Wildeman are glad that a comprehensive explanation has finally arrived….

Click here to continue reading.

Newer rock drawings are clearly distinguishable from those hundreds of years old. Photos by DFC.

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