Cells of Halococcus dombrowskii following exposure to a simulated martian UV flux and subsequent staining with the LIVE/DEAD kit. Red: nonviable cells due to damaged membranes; green: viable cells with intact membranes. Insert: Scanning electron micrograph (photo by Chris Frethem, CharFac, University of Minnesota) of a typical small aggregate of the coccoid cells of Hcc. dombrowskii.