Free Astronomy Magazine January-February 2019

45 JANUARY-FEBRUARY 2019 few weeks or months, ensuring the integrity of the vital load. Unfortunately, the more those planets are studied, the less they seem hospitable to life as we know it. The great- est unknown concerns the existence and consistency of atmospheres, as well as the presence of land. According to a study by re- searchers from Arizona State University and Vanderbilt University, between 20% and 50% of the mass of TRAPPIST-1 planets would consist of water (Earth = 0.2%). The deep global oceans that, in this case, would cover the planetary surfaces would inhibit the geochemical cycles necessary to main- tain an atmosphere and would instead favor the “snowball” effect. Since there are no better candidates, we just have to wait for new discoveries. Find- ing any evidence of life, even as a fossil, on Mars that shares chemical similarities with life on Earth, or recognizing identical bio- markers in the atmospheres of two exo- planets of the same extrasolar system, could lend support to the panspermia hypothesis, and our conception of the diffusion of life in the cosmos would radically change. O n the right, some speci- mens of Bacillus pumilus. Microor- ganisms of this type can form en- dospores − tough, dormant, and non-reproductive structures that allow it to survive harsh conditions and extreme envi- ronments. The tough shells of the endospores pro- vide the organism with the means to protect its genetic material from cos- mic radiation and other factors. [Science Photo Library] in the future will help other re- searchers to estab- lish whether, from the dynamic point of view, pansper- mia is possible in multiple planetary systems. In a system struc- tured like TRAPPIST- 1 it is very probable that elementary forms of life are able to move from one planet to an- other, because the interplanetary jour- ney of the material in which they could take shelter would be quite short, on average. Note that stellar and cosmic radiation ex- posure is the worst threat to the pansper- mia hypothesis. The experiments con- ducted so far tell us that colonies of ex- tremophile bacteria ex- posed to outer space in low Earth orbit can survive well over a year if sheltered by the rock. Under ideal conditions of protection, a very large colony can probably survive for decades or cen- turies. What if there were extraterrestrial forms of life able to survive in space for mil- lennia? In the TRAPPIST-1 system, the three phases of panspermia could occur within a !