Man's relentless search for signs of life beyond our planet may just have found it. The scientists have not (yet) claimed to have found evidence of life, only for “anomalous and unexplained chemistry”. But, as Sherlock Holmes famously said to Dr Watson: “Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.”
Earth’s sister planet, Venus, has not been regarded as a high priority in the search for life as its surface temperature of 450°C and thick, sulphurous and acidic atmosphere was therefore thought to be hostile to even the hardiest of micro-organisms.
We have only had the briefest of glimpses of a barren landscape from the two Russian landers that made it down to the ground back in the 1980s. So it’s no wonder that a report published in Nature Astronomy that the upper levels of Venus’ atmosphere contain a molecule that is a potential signature of life, comes as something of a shock.
The molecule in question is phosphine. It's a highly flammable, extremely smelly toxic gas, found (among other places) in penguin dung and the bowels of badgers and fish. It's present in Earth’s atmosphere in only miniscule quantities because it is rapidly destroyed by the process of oxidation. The fact that this molecule is nevertheless present in our oxidising atmosphere is because it is continuously produced by microbes. So phosphine in the atmosphere of a rocky planet is regarded as a strong signature for life.
It shouldn’t be stable in the atmosphere of a planet like Venus where it would be rapidly oxidised unless, like on Earth, there's a constant new supply. So why were the authors of the study looking for phosphine in such an unpromising environment? And are they certain that they have found it?
Reading between the lines of the report, it seems that the team was not expecting to find phosphine. Indeed, they actively seemed to be looking for its absence. Venus was to supply the “baseline atmosphere” of a rocky planet, free from a phosphine biosignature. Scientists investigating rocky exoplanets would then be able to compare the atmospheres of these bodies with that of Venus, to identify any potential phosphine biosignature.
So to find a global concentration of the molecule around 1,000 times higher than that of Earth was something of a surprise. To say the least.
However, the authors do not claim to have found evidence for life, only for “anomalous and unexplained chemistry”. But, as Sherlock Holmes said to Dr Watson: “Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.”
Original source: theconversation.com