The Mauritanian Sahara after a rainy day. (IMAGE) Proceedings of the National Academy of Sciences Caption The Mauritanian Sahara after a rainy day. Credit Image Credit: Rachid Cheddadi Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.