Are we alone in the universe? It’s a question that has plagued mankind for ages; a question that has sent many an imagination sparling into fantasy and invention. Even the discovery of tiny, microscopic microbial life would have paradigm shattering implications for the human race: It would confirm the existence of extra-terrestrial life; it would reveal totally new evolutionary histories, and lifeforms; create entirely new realms of biological study; and it would change humanity’s understanding of the universe we live in.

So far, though, we’ve only been able to speculate on that question. Without any real scientific evidence of life on other planets, we’ve been left alone and in the dark.

Until now.

On September 14th, an international group of astronomers published a paper called "The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere." In which, they claim to have discovered something very interesting, very close to home. Specifically (and surprisingly) on Venus — a planet that has long been dismissed as hellish and unfit for life. High in the atmosphere of that chloric world, these scientists discovered signatures of a molecule called phosphine. And it might just be the biggest scientific discovery of the century.

Why? One might ask. What’s the big deal with atmospheric phosphine in a place like Venus?

Well, for one: Phosphine is what astronomers call a “biosignature.” Astronomers have been using biosignatures to look for life for a long time — as the name suggests, the presence of these specific molecules indicates a biological agent, as they rarely occur under natural conditions. That is to say, the presence of biosignatures typically indicates the presence of life.

Common biosignatures astronomers look for are oxygen, methane, nitrogen and (you guessed it) phosphine.

Phosphine is an interesting chemical. As far as humans understand, large quantities of it can only be created in two ways: either in a lab, under controlled conditions; or by a living organism. It’s a pretty standard thing to look for, when examining other earth-like planets, in the search for life.

So, when these scientists pointed a submillimeter radio telescope at Venus (notably, just to get a benchmark for future observations) they were blown away to discover quantities of phosphine floating high above yellow planet’s surface. It was so surprising, they got another, more powerful radio telescope and took a second look. Sure enough, the results were the same: Venus has phosphine. 

That wasn’t the only exciting aspect of this discovery, though. Because, not only did they discover this biosignature in large-enough quantities to raise eyebrows, but they discovered it in a very specific, very thin layer of Venus’ atmosphere: the only potentially habitable zone on the planet. Venus is a notoriously inhospitable place — the air itself is filled with noxious chlorine gas; the surface temperatures hang around 875 degrees F (hot enough to melt lead); the days are longer than the years, and oddly, it rotates backwards.

However, there is a very thin layer of Venus’ atmosphere which scientists have long-hypothesized, could harbor life. There, (between 48 and 60 kilometers above the surface) the temperatures are mild and the conditions are stable. If life existed anywhere on Venus, most scientists agree, it would likely be found in this “temperate zone.”

Figures courtesy of The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere (2020).

Lo and behold, that’s exactly where these biosignatures were detected. Between the amount of phosphine observed and the consistency of its presence in this layer, the question of ‘Are we alone in the universe?’ might finally have an answer: No.  

Now, this doesn’t mean there are cloud cities floating around the habitable zone of Venus. And while it could mean that there are advanced multi-cellular animals existing there (like sky whales flying over the yellow wasteland planet, or massive kite-like alien jellyfish blotting out the sun) it probably doesn’t. More likely, this phosphine is the result of some microbial lifeform, like bacteria that has somehow evolved to keep itself held aloft, tens of thousands of feet above the ground.

Now, many of you are likely skeptical of these findings and the conclusions that scientists are drawing from them. That’s good. Because, this is far from proof of alien life on another planet. Instead, it’s just very good evidence. In fact, this is arguably the best evidence we’ve ever had that life exists outside of this planet. And lucky for us, it’s right next door (closer than Mars even!) — sending a drone or probe to Venus, to further investigate this will be a relatively easy ordeal.

Still not sold? That’s okay — because, neither were the scientists who first observed this. In their paper, they dedicate a significant portion of their research trying to offer alternative explanations for this phosphine discovery. They do their best to thoroughly explain this some other way: Is the phosphine content of Venus’ habitable zone the result of volcanic discharge? Was it left there by a comet? Could our own microbes, flying on our own Venus probes, have left these phosphines behind?

Not probable, not likely and no. According to the paper, the amount of phosphine observed is unlikely to have come from a volcano, Earthly probe or comet. Whatever is producing it, has been doing so for a very long time. No recent change or interaction could have generated so much of this biosignature.

It seems that the most likely explanation, so far, is extraterrestrial life. That’s a discovery that could change our understanding of everything — from science, to spirituality, civilization, history and life on Earth. If it turns out that this phosphine is the result of life on Venus, it means that we are not alone — not even in our own solar system.