THIS PROPOSAL IS BASED ON A PRELIMINARY EXPERIMENT WITH FRESHWATER ALGA CHLORELLA WHICH INDICATES THAT A CA BRINE CAN BE UNINHABITABLE EVEN THOUGH ITS WATER POTENT IS BIOLOGICALLY PERMISSIBLE. THIS RESULT IS CONSISTENT WITH FRANZ HOFMEISTER S 1888 DISCOVERY THAT CA IS A CHAOTROPIC ION THAT DESTABILIZES PROTEINS AND BIOLOGICAL MOLECULES WHEREAS NA IS HARMLESS (BEYOND CREATING OSMOTIC STRESS) OR STABILIZING I.E. KOSMOTROPIC. IN OTHER WORDS THE TERM WATER POTENTIAL DOES NOT CAPTURE ALL ASPECTS OF THE IONIC STRESS INHERENT IN A CA BRINE. THE PROPOSED ONE-YEAR PILOT STUDY WILL EXPAND THIS INQUIRY TO INCLUDE FIFTEEN HALOPHILC CYANOBACTERIA BACTERIA AND ARCHAEA THAT HAVE BEEN ISOLATED OR TO BE ISOLATED FROM LAKE VIDA IN THE ANTARCTIC DRY VALLEYS HOT LAKE IN WASHINGTON STATE AND THE DEAD SEA. OUR GOAL IS TO TEST THE PREDICTED HALOPHILIC HOFMEISTER SERIES CA>MG>NA (FROM THE MOST CHAOTROPIC TO THE MOST KOSMOTROPIC) AND TO SHOW THAT THE PRESENCE OF NA CAN MITIGATE THE CHAOTROPIC EFFECT OF CA AND MG. SPECIFICALLY WE WILL DETERMINE EACH ISOLATE S OSMOTIC TOLERANCE FOR NACL MGCL2 AND CACL2 AND IN THE LATTER TWO CASES BOTH IN THE PRESENCE AND ABSENCE OF NACL. VIRTUALLY ALL ASTROBIOLOGICALLY INTERESTING ENVIRONMENTS ON MARS AND EUROPA ARE HIGH CA OR MG SALINE ENVIRONMENTS. IF OUR THESIS IS CORRECT HABITABILITY ASSESSMENT THERE MUST TAKE INTO CONSIDERATION THE DEGREE OF CHAOTROPICITY AS WELL AS THE OSMOTIC POTENTIAL OF THE BRINES.