Abstract
To investigate whether terrestrial life (TL) can survive in interstellar and interplanetary space, an experiment was performed to simulate conditions in the Earth's orbit. There are many factors which influence survivability. Among them, the effects of temperature fluctuations and UV irradiations were addressed in this paper. Six species of moss spores and 3 species of fungal spores were selected as target TL. Temperature was fluctuated between 80˚C and -80˚C once every 90 min, whereas UV at 254nm was irradiated for 10 min (471mJ/cm2) and 30 min (1,413mJ/cm2). The moss spores of Funaria hygrometrica (exp 1) and Pogonatum inflexum (exp 2) were the most tolerable species to the thermal cycle treatment, with germination rates of 3.3±1.2% (n=5) and 7.9±3.2% (n=6), respectively, after 3 weeks of treatment. Germination occurred even after the spores had been UV irradiated for 30 min (0.7% to 23.5%). Only a slight difference in the germination rate was observed using different culture media. The treated spores were transferred to soil where they grew into gametophytes, then sporophytes, and finally formed new capsules after 7-8 months. Two species of fungal spores were allowed to adsorb onto beads before the beads were directly irradiated for 10 min and 30 min, respectively. Colonies developed the spores irradiated for 30 min. On the other hand, a colony did not develop if the spores were taken off the beads and irradiated for 10 min. This indicates that UV does not penetrate to the other side of the beads, and so the spores on that side can be protected from UV radiation.
