LIFE IN EXTRATERRESTRIAL ENVIRONMENTS
The objective of this program was to establish whether terrestrial life forms can survive and thrive in extraterrestrial environments. Other than Earth, the only solar body capable of supporting terrestrial life appears to be the planet Mars. The conditions selected to simulate a Martian environment were determined by a literature search and were: 1) Light of > 4800-A wavelength 2) Temperature changes from a diurnal high of 30 °C to a nocturnal low to -60 °C 3) Atmosphere composed of 95% nitrogen, 4% argon, 0.3% carbon dioxide, and less than 1% oxygen and moisture. The organisms tested in thesimjulated Martian environment were: 1) Algae: Trebouxia erici 2) Bacteria: Clostridium tetani, Bacillus subtilis, and Escherichia coli 3) Bryophytes: the liverwort Marchantia polymorpha; the mosses Eurhynchium strigosum, Atrichum undulatum, Mnium sp., Brium sp., Grimmia sp., Pogonatum sp., and Polytrichum sp. 4) Lichens: Cladonia conoeraea, C. rangifernia, C. cristatella, C. pyxidate, Parmelia conspersa var. isidata, P. conspersa var. leucophora, Lecidea cyanea, Umbilicaria dillenii, Physcia hypoleuca, and Ramalina sp. T. erici survived for about 2 weeks. C. tetani and E. coli cells decreased rapidly in number, but the tetanus toxin remained active for the 127=day period of the experiment. B. subtilis cells increased in number. Of the Bryophytes, only one moss survived. Complete results for the lichens are not yet available. It is suggested that the observed color changes on the Martian surface may be explained in part by color changes in the surface vegetation as a function of moisture content.