As it has been rumored for a few days now, Nature has just published that we have found significant amounts of phosphine on Venus. A team of researchers from four universities (Cardiff University, Manchester University, Cambridge University and the Massachusetts Institute of Technology) used the James Clerk Maxwell Telescope in Hawaii and the ALMA radio astronomy complex in Chile to identify the gas within the atmosphere of our neighbouring planet.
Phosphine — also known as phosphane (PH3) — is a colorless, flammable gas that smells like garlic or rotten fish. None of this is what makes it interesting: the main thing is that it is produced, naturally, when organic matter is degraded. On Earth, in fact, biological is the main source. That is why in some contexts it has been proposed as a sign that there is life on that planet, especially on temperate exoplanets.
However, this does not necessarily mean that there is life on Venus, nor is it something especially unique to the planets around us. Already in 2009 Cassini found phosphine on Jupiter and Saturn or in the tail of the comet Chury. The key would be elsewhere: in its quantity. What exactly does it mean that there is phosphine on Venus?
As far as we know, with an average temperature that exceeds 450 degrees and an atmospheric pressure 90 times that of the Earth, it is very difficult for life to exist on the surface of Venus today. However, this is the result of a huge greenhouse effect that is devastating the country; at the time, Venus was indeed habitable at some point in its history. For that reason, Carl Sagan himself came to conjecture the possibility that there are certain extremophiles that could inhabit a certain layer of its atmosphere (some 55 km from the ground and with much more reasonable temperatures — between 20 and 30 degrees). However, there is no clear evidence about this.
But it was not enough to find phosphine: it was necessary that the data found on the planet did not give much room to speculation of another kind. To be able to talk about “strong evidence” that there is life on Venus, we need a puzzle that can only be solved by the existence of biological organisms.
And that, in light of Nature’s article, is what we have. In it, the authors point out that the quantities they have found are so large that, although they have reviewed “all the possible processes that could produce phosphine on a rocky planet,” they have not been able to explain them without including some kind of life in the equation.
Over the years we will know if the data were wrong, if there is another explanation or if, finally, we have found living organisms outside of planet Earth.