Phosphine is one of the grossest chemicals out there. Not because of what it’s made of–one atoms of phosphorus and three atoms of hydrogen–but because it’s really, really stinky. It’s commonly associated with decaying organic matter, if you need a mental picture. It occurs naturally through a variety of processes, most notably as a byproduct of non-oxygen-using life. But since oxygen-using life is quite common on our planet, thankfully this stinky chemical is relatively rare.
Recently some astronomers have been raising a big stink (pun very much intended) about Earth’s sister planet, Venus. For those of you new to Venus: don’t go. It’s a nightmarish hellhole of a planet, choking on so much poisonous carbon dioxide that its surface pressure is over 90 times that of sea level. The temperatures at the surface are hot enough to melt lead. It rains sulfuric acid.
It’s nasty. And it just might–might – be a home for life.
A certain subgroup of astronomers known as astrobiologists (and yes, that’s a thing) are hunting for signs of life outside the Earth. One of the most promising ways is to look for (and this is a pretty awesome jargon word) biosignatures. These are signs of life in the form of chemicals that don’t normally come from chemical (i.e., boring unless you’re a chemist) processes.
An example of this is oxygen. The vast majority of the oxygen in our atmosphere comes as a byproduct of photosynthesis (in other words: life). If we were to find a lot of oxygen in another planet’s atmosphere, it just might be teeming with little critters.
Another potential biosignature is stinky molecule phosphine. Sure, it’s possible to create phosphine naturally, but it takes a lot of energy, and is very unstable–the UV radiation from the sun does a really good job at breaking it apart.
I’ll cut to the chase: a group of astronomers recently announced the presence of a load of phosphine in the atmosphere of Venus. A potential sign of life in basically the last place you would expect to find it.
Now we also see a lot of phosphine in the atmospheres of Jupiter and Saturn, and we really don’t think it comes from life on those giant planets–more likely it originates in some super-intense chemical process deep in their interiors.
The astronomers argue that they’ve thought of every possible way to make lots of phosphine in Venus without involving life, and keep coming up short.
Where could life exist in that hellscape? Well, a few dozen miles up in the atmosphere is pretty clement: room temperatures and standard air pressures. The air is still full of noxious carbon dioxide and sulfuric acid, but hey life has found footholds in stranger places.
But still, as with all stories of this nature, I urge caution and skepticism. Venus is a strange, strange environment that we barely even pretend to understand. Lots of crazy chemistry could be going on. There have been hints of life on Mars for decades that have been undermined by further study, and the same is likely true for Venus. By the time the news excitement dies down, there is likely to be a dozen hypothetical processes proposed that could explain the strange presence of phosphine on Venus.
Which is exciting if you’re into cool, weird chemistry, but not so exciting if you’re into life.