Venus, Earth's sister with a sulfuric acid atmosphere, seems inhospitable. What could possibly survive on such a blistering-hot planet?
Image of Venus constructed through data from NASA's Mariner 10 spacecraft (1974). JPL // NASA
On Sept. 14, astronomers announced the detection of phosphine gas in Venus's atmosphere. It was discovered lurking in sulfuric acid clouds surrounding the planet - only in small trace amounts, according to an astrophysicist at the Imperial College of London. So, what's the big deal?
“It’s equivalent to a few tablespoons in an Olympic sized swimming pool,” - David Clements, an astrophysicist
Well on Earth, phosphine gas is artificially manufactured by humans - or it's a natural byproduct of life. Typically, it's produced by microbes and found in swamps or marshlands. Additionally, the molecule can be found in the guts of animals. In sum, phosphine gas is almost always associated with life.
We're left with two possibilities: these small trace amounts were produced by an unknown chemical interaction - or life. Sara Seager, an MIT planetary scientist, and her co-workers published their speculations on possible alien life on Venus this summer, before the grand discovery. They hypothesized a living rain of microbes inhabiting droplets of sulfuric acid in the clouds.
"We did exhaustively search through all known chemistry ... and we didn’t find anything that could produce more than the tiniest amount of phosphine in Venus’s atmosphere," - Sara Seager, planetary scientist
Aliens? Not Quite
In 1996, Earth was rocked by the discovery of fossilized bacteria in a Martian meteorite. Except... that evidence didn't quite hold up. The astronomical community has been down this road before, discovering "alien life" in our solar system. However, those claims don't stand under closer scrutiny.
In this situation, we have to begin by verifying that the gas is, in fact, phosphine. Detecting biosignatures, although one of the astronomer's best methods in locating life, isn't always credible. According to researchers, this signal could be explained by another gas, sulfur dioxide.
“We’re in a “Let’s wait and see,” kind of situation. I think it’s a very intriguing discovery, but it definitely needs to be explored more.” - Victoria Meadows, an astrobiologist
Furthermore, alien life isn't a definite explanation for the presence of phosphine gas. Venus, seemingly, is a barren wasteland. Temperatures soar to 900 degrees Fahrenheit, and pH levels are well above measurable. Although Venus's sulfuric acid clouds have moderate temperatures, the planet's still a difficult place for any organism, even microbes, to survive.
"There’s nothing definitive saying it is biology. There’s still a lot of unknowns. And it’s nice to put biology as the answer, but really, as scientists, we need to back it up and make sure we exhaustively study all the other possibilities." - Rakesh Mogul, biological chemist