QUICK FACTS
The place is it? Guérou, Mauritania [16.930575400, -11.759622605]
What’s within the photograph? Three black mesas surrounded by uncommon sand dunes within the Sahara Desert
Who took the photograph? An unnamed astronaut onboard the Worldwide House Station (ISS)
When was it taken? Could 3, 2023
This intriguing astronaut photograph reveals a trio of historic “black mesas”, which sit side-by-side within the Sahara desert. The darkish buildings have enabled a sequence of uncommon sand dunes to type round them whereas additionally making a shocking “dune-free zone.”
The darkish colour of those round hills is the results of “rock varnish” — a black, clay-based coating, wealthy in manganese and iron oxides, that varieties on uncovered and arid rocks over hundreds of years, in accordance with NASA’s Earth Observatory. This coating was probably partly mounted in place by microorganisms and is made up of a number of micrometer-thick laminations, in accordance with Science Direct.
To the west of the mesas (on the left of the photograph) is a barren rocky plain with a shocking lack of sand dunes. However to the east of the flattened hills, you’ll be able to see a number of sizable dunes which are seemingly flowing away from the black rocks like a rippling tail.
There are two fundamental forms of sand dunes seen within the picture. The primary kind are uncommon “climbing dunes,” that are the bigger, ridge-like piles of sand which have piled up alongside the mesas’ jap partitions. The second kind are “barchan dunes,” that are extra widespread and make up the mesas’ stripy tail. In each instances, the dunes have a particular reddish-yellow hue.
The sand dunes solely type on the jap facet of the mesas as a result of the wind predominantly blows from that path, carrying sand that then will get caught on the sloped elevations surrounding the black rocks.
Sand doesn’t accumulate to the west of the mesas due to a phenomenon referred to as “wind scour,” which ends from superfast vortices inside the wind that will get squeezed in between the mesas, which blow sand away from the flattened hills, in accordance with the Earth Observatory.
One other astronaut photograph, taken in 2014, reveals this odd impact over a bigger space (see under). On this shot, you’ll be able to see the barchan dunes lengthen a lot additional away from the mesas within the photograph, in addition to one other bigger mesa additional east.
In the course of the Paleozoic period, which lasted from 541 million to 251.9 million years in the past, all these mesas have been probably a part of a single huge rock formation that has since been damaged up by millennia of water and wind erosion, in accordance with the Earth Observatory.
This formation might have been just like the Richat Construction — an enormous set of concentric rings of rock, also referred to as the “Eye of the Sahara,” which is situated in Mauritania round 285 miles (460 km) north of Guérou.
Mesas will be discovered throughout the globe however there’s a significantly excessive focus of them within the Sahara, in addition to all through components of the U.S., reminiscent of Colorado, New Mexico, Utah, and Arizona, in accordance with the Nationwide Park Service.
Elsewhere within the photo voltaic system, mesas are a distinguished geological function on Mars, having been carved out of the Pink Planet by billions of years of wind erosion, in accordance with Reside Science’s sister web site House.com.
For extra unbelievable satellite tv for pc images and astronaut photographs, try our Earth from area archives.
