MSGID: 1:317/3 639f554f   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
   December 18, 2022 - Richat Structure   
      
      Richat   
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      This true-color image of the “Blue Eye of the Sahara” was acquired by   
      the Moderate Resolution Imaging Spectroradiometer (MODIS) on board   
      NASA’s Aqua satellite on December 15, 2022.   
      
      The startling circular structure, more properly known as the Richat   
      Structure, is a geological formation in Mauritania’s sand-swept Maur   
      Adrar Desert, which is also part of the Western Sahara Desert. The   
      peculiar round shape, with concentric rings of ancient weathered rock,   
      tucks in close to spectacular rocky cliffs—and both are surrounded by   
      vast orange-toned sand seas, where the ripples of tall dunes are easily   
      seen from space. Combined together, this feature has captured the   
      interest of scientists ever since it was first photographed by the   
      Gemini crew in the 1960s.   
      
      Early speculation was that the round shape was the result of an impact   
      crater created when an object fell from space and struck the Earth’s   
      surface. Further study shows that the Richat Structure was initially   
      formed primarily by volcanic activity many millions of years ago,   
      roughly around the time that the supercontinent of Pangea began to pull   
      apart. During that turbulent time, a lengthy series of eruptions   
      created a volcanic dome, which hardened into an elliptical shape. The   
      slow erosion by wind and water (the region was not always desert)   
      slowly exposed the onion-like rings that we see today. The rocks that   
      form the center of the Richat Structure are older than those found in   
      the outer rings.   
      
      Image Facts   
      Satellite:  Aqua   
      Date Acquired: 12/15/2022   
      Resolutions:  1km (69.6 KB),  500m (171.6 KB),  250m (82.8 KB)   
      Bands Used: 1,4,3   
      Image Credit: MODIS Land Rapid Response Team, NASA GSFC   
      
      
      
   https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2022-12-18   
       
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