Discovery and microbial content of the driest site of the hyperarid A tacama D esert, C hile

Summary The A tacama D esert is the driest and oldest desert on E arth. Eleven years ago, the Y ungay region was established as the driest site of this hyperarid desert and also close to the dry limit for life on E arth. Since then, much has been published about the extraordinary characteristics of this site and its pertinence as a M ars analogue model. However, as a result of a more systematic search in the A tacama here, we describe a new site, M aría E lena S outh ( MES ), which is much drier than Y ungay. The mean atmospheric relative humidity ( RH ) at MES was 17.3%, with the RH of its soils remaining at a constant 14% at the depth of 1 m, a value that matches the lowest RH measurements taken by the M ars S cience L aboratory at G ale C rater. Remarkably, we found a number of viable bacterial species in the soil profile at MES using a combination of molecular dependent and independent methods, unveiling the presence of life in the driest place on the A tacama D esert reported to date.