Western Slope Skies - Phosphine & Venus

Oct 16, 2020

Concept for a Venus Airplane
Credit NASA

Astronomers announced the surprising possibility of life on Venus last month, based on the discovery of phosphine in the atmosphere. What is phosphine? And are we really ready to reclassify Venus from scary greenhouse-effect nightmare to potentially livable place?

The word phosphine may sound like shimmery fairy dust, and perhaps you’re already imagining a delicate floating ecosystem full of aerial jellyfish. However, phosphine is a stinky gas produced by things like rotting plants and penguin poop. Here on Earth, it can be toxic; phosphine is produced when rat poison mixes with water. The chemical structure is one phosphorus atom linked with three hydrogen atoms. Like methane, astronomers are more interested in its origins than its smell. The only known ways on Venus to make phosphine all involve life.

The team that discovered Venusian phosphine, led by astronomer Jane Greaves, was testing a way to remotely sniff the atmospheres of distant exoplanets, planets orbiting other stars, for the possibility of life.
Unlike those tantalizing exoplanets, Venus is close enough to ground truth. Since the discovery, astronomers have been examining all the data. Imagine the surprise when scientist Rakesh Mogul discovered that an early NASA Pioneer Mission caught a whiff of phosphine on Venus – way back in 1979. Pioneer Venus 2 had dropped a probe to learn about the atmosphere. That mission focused on major components, like carbon dioxide. Phosphine went unnoticed.

Perhaps our prior knowledge was blocking our view. We’ve been thinking of Venus as an unpleasant place since the late 1960s, when several Soviet craft were crushed by enormous pressure even before landing. Spacecraft data revealed a broiling surface where, according to Neil DeGrasse Tyson, you could cook a pizza in 9 seconds. Even Venus’s brilliance in our night sky is due to reflective clouds of dangerous sulfuric acid. Can you blame us for labeling it un-survivable?

The discovery breathes new life into speculations of habitability in clouds. Around 50 kilometers up, temperatures drop from about 900 degrees Fahrenheit to a more comfy 30-200 degrees. This is where the phosphine was found.

The US hasn’t sent a mission dedicated to Venus in over 30 years, and it is clearly time to take another look. The exploration of what life could be, and where it could survive is far from over, even in our own solar system. It’s a good reminder to open the door to surprise, especially if you think you already know.

You’ve been listening to Western Slope Skies, produced by the Black Canyon Astronomical Society. This episode was written and recorded by me, Alice de Anguera, a park ranger at Black Canyon of the Gunnison National Park.