As I prepared to write this column, some intriguing space news broke, an announcement by an international team of astronomers that they had found evidence of the rare compound phosphine high in the clouds of Venus using spectroscopy, the study of how light (or other forms of electromagnetic radiation) shows evidence of interaction with matter in the spectra it produces. They duplicated their finding on two different instruments. Phosphine is a notable find because it’s considered a biomarker.

Ongoing biological processes, i.e. life, are the only thing we know of that would produce phosphine at the levels observed on Venus. Imagine anaerobic microbes floating in the sulfuric acid clouds high above Venus, where, by the way, the temperature is a tolerable 80 degrees Farenheit, not the 900 degrees or so it is on the planet’s surface. As amazing as this is, it’s not proof of life. It’s more like evidence of evidence of life. The team could be wrong about the phosphine, or there could be some non-biological process unknown to us that produces it. Still, it’s intriguing to note that there are features in the atmosphere of Venus that block or absorb ultraviolet light. A 2018 study found these features to be composed of something very small, about the size of bacteria on earth. Phosphine on earth is produced by anaerobic bacteria in rotting carcasses. Again, intriguing!

Ian Clarke is the director of the Hatter Planetarium at Gettysburg College. More information available at

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