Free Astronomy Magazine November-December 2020

6 NOVEMBER-DECEMBER 2020 ASTROCHEMISTRY lecular detection and an interpretation in the absence of any known non-biological explanations. That said, one can only imag- ine the instinct to be the first to make such a discovery, however preliminary, known to the world as soon as possible. What has followed is a story of measure- ment, interpretation, reserved speculation, and controversy − not over the discovery of phosphine, but over its indication as a pos- sible biological marker, which has driven discussion beyond just the astronomical community. What is most clear is how little we still know about our own solar system, as a simple molecule can lead to heated debate because of our incomplete under- standing of the chemistry and geology of our near- est planetary neighbors. What we know and do not yet know about the production of phosphine, PH 3 , on Venus are central to the past few weeks of speculation. On Earth, phosphine can be pro- duced by lightning and volcanism, both common on Venus. That said, the atmos- pheric and geochemical routes to phos- phine could only account for a fraction of the amount detected based on our current understanding of both phenomena. The possible explanation put forth by the au- thors applies the predominant method of phosphine production on Earth – biochem- ical processes in low-oxygen conditions. As is obvious from the many design fea- tures of the few successful Venera and Pio- L eft, a false- color enhance- ment of an origi- nal photograph of the opaque Venus cloud cover taken by Mariner 10 during its gravity-assist maneuver en route to Mercury in February, 1974. [NASA/JPL] Right, the surface of Venus as cap- tured by the Magellan space- craft. [Magellan Project/NASA/JPL] On the side, an artistic enlarge- ment of a tiny region of the Venusian atmos- phere, showing the geometry of the phosphine molecule. [ESO]