The Sahara Desert is one of the driest places on Earth but a mighty river once flowed through it. Evidence of the river network, which used to carry water for hundreds of miles across Western Sahara, was found by a satellite buried in the sands of Mauritania.
Much of Sahara's expanse may no longer be hospitable to life now but this has not always been the case. The region used to have grasslands where animals fed. Humans, who left behind rock arts, also thrived in the region.
Scientists theorized that an ancient river drained that land and the mega lakes, one of which is believed to be larger than the Caspian Sea. Researchers called this lost river the Tamanrasett.
In an attempt to find evidence of this lost river, Charlotte Skonieczny from the French Research Institute for Exploitation of the Sea (IFREMER), and colleagues turned to Palsar orbital radar satellite imagery, which is capable of penetrating meters of material such as sand dunes and map the geological features beneath it.
The technique allowed the team to reveal the existence of an ancient river network spanning about 323 miles in length. Writing in the journal Nature Communications, the researchers said that if the river system continued to flow today, it would have ranked 12th largest on Earth.
The river would have helped plants, wildlife and people thrive in what is now one of the world's most inhabitable lands. It would have also transported nutrients that are crucial for organisms in the sea.
"It's a great geological detective story and it confirms more directly what we had expected. This is more compelling evidence that in the past there was a very big river system feeding into this canyon," said Russell Wynn, of the National Oceanography Centre in Southampton, who was not involved in the study. "It tells us that as recently as five to six thousand years ago, the Sahara desert was a very vibrant, active river system."
The results of the study have crucial implication on how sediment records off West Africa are interpreted as well as on current understanding of a wetter and greener Sahara.
"This finding provides new insights for the interpretation of terrigenous sediment records off Western Africa, with important implications for our understanding of the paleohydrological history of the Sahara," the researchers wrote in their study.
