Life on... Venus?

Giles Manning reports on the recent detection of phosphine gas on Venus and how this impacts our current understanding of the origin of life in the universe.

While David Bowie and pop culture would have us think that Mars is the most likely place in our solar system to harbour life, recent research published in Nature Astronomy suggests that we should in fact be looking in the other direction. What does the detection of phosphine gas on Venus mean for our understanding of life beyond Earth?

In September 2020, an international group of astronomers detected the presence of phosphine gas in the atmosphere of Venus. Specifically, it was found within the planet’s notoriously thick, acidic clouds. This is significant because, to our current understanding, phosphine gas is not produced without the presence of microbes or via man-made chemical reactions. Multiple groups around the world are now interrogating this finding by corroborating the published data with observations from different telescopes. Nevertheless, if found to be true, what implications would this have for the occurrence of extraterrestrial life—not just within our solar system, but the wider universe?

To our present knowledge, the only life in existence is on Earth. Abiogenesis, the technical term for the origin of life from non-living substances, has fascinated scientists for centuries. How did simple organic matter transform into the abundance of living organisms present on our planet today? Much work has gone into understanding the mechanisms through which non-living chemicals could have assembled into systems which we define as ‘alive’.

There are some who believe that life originated on Earth itself, with early planetary conditions allowing molecules to arrange themselves into living, replicating systems. This does not mean that life couldn’t exist elsewhere, but it does decrease the probability.

The alternative theory of panspermia states that the seeds of life already existed in the universe before coming to Earth. Like spores diffusing through space searching for a place to call home, panspermia suggests that precursory molecules or microorganisms arrived on Earth via meteoroids or other celestial bodies. This would suggest that life is widespread throughout the universe. Whilst the possible discovery of life on Venus wouldn’t prove or disprove either of these theories, it could certainly indicate that the conditions required for life are more common than previously thought.

If Venusian life does really exist, it could transform the way we perceive and approach the search for extraterrestrial life. As disappointing as it is that we haven’t spotted big green aliens through a telescope, it certainly is an exciting prospect that there could be life forms on our doorstep, just waiting to be discovered.

From Issue 21