Free Astronomy Magazine November-December 2020

9 NOVEMBER-DECEMBER 2020 ASTROCHEMISTRY Sagan in 1961, titled “The Planet Venus.” In it, he comments on the likelihood of de- tecting life on the sur- face: “...it appears quite certain that ter- restrial organisms de- posited on the surface of the planet would quickly be killed. Con- sequently, there seems little danger of biolog- ical contamination of the surface of Venus.” Enough was then known about the Venusian atmosphere that its possible hosting of simple lifeforms could not so easily be ruled out. Sagan wrote: “conditions are much more favor- able at higher altitudes, especially just be- neath the cloud layer, and there is the distinct possibility of biological contamina- tion of the upper Cytherean atmosphere.” The most recent data-driven analysis of Ve- nusian life harkens back to the days of Per- cival Lowell and his Martian canals, with the Russian scientist Leonid Ksanfomaliti claiming to have found life in images sent back from the Soviet Venera 13 lander mis- sion in 1982. The consensus now is that the disc-like and scorpion-like creatures were, in fact, lens caps and processing artifacts – a clear example of the inverse relationship between data and speculation. Anyone basing Venusian life on the single- celled organisms inhabiting ponds on Earth would have to take dramatic leaps in biol- ogy to make such organisms robust enough to survive the hyper-acidic, poisonous, and water-poor conditions of the upper Venu- sian atmosphere. That said, similar leaps already abound on Earth. A few examples include thermococcus gammatolerans , which can survive high doses of gamma radiation, pyrococcus furiosus , which thrives at the boiling point of water (we sim- ple surface-dwellers rely on boiling water to kill harmful bacteria), or clostridium para- doxum , which is found in acidic mine drainage and volcanic springs. Extreme conditions call for extreme adaptation. We find organisms on Earth exist- ing in places, including the upper atmosphere, where we would not even think to look for them if not for the constant reminder that life, within a very wide range of environ- ments, always finds a way. Even without an actual life- form, the presence of certain small molecules in planetary T his video summarizes the discovery of phosphine in the atmosphere of Venus. [ESO] Below, the unfor- gettable Carl Sagan (with the famous message sent on Pioneer probes), who, sixty years ago, had already hy- pothesized the possible existence of life in the up- per atmosphere of Venus. [CBS via Getty images]