No dewfall or frost in the Antarctic Dry Valley summers: Comment on Büdel et al. (2008).

Microbial communities within porous rocks in the upper elevations of the McMurdo Dry Valleys of Antarctica are an interesting analog for life on Mars. The primary source of moisture for this community is summer snowmelt adsorbed by the porous stone. Büdel et al. (2008) suggested that dewfall/frost may be an alternative and frequent source of water, implying that in comparison to other prokaryotic communities in which the apparent use of dew by prokaryotes was challenged (cyanobacterial soil biocrusts and lithic cyanobacteria in the Negev), this community stands out as one that presumably utilize dew/frost. By assuming the utilization of a frequent source of water, the authors concluded that this community cannot be regarded as inhabiting the "edge of life" as often suggested. Nevertheless, over almost 50 years of investigation of these systems, this is the only report of dew/frost in the summer. We believe that this report is in error due to faulty temperature measurements of the rock surface and miscalculation or misuse of the condensation theory.