When looking for extraterrestrial life, Earth’s sister planet Venus was not given priority. It is believed that its surface temperature is about 450°C, even the most resistant microorganisms can be hostile, and its dense, sulfur-containing and acidic atmosphere makes the surface almost completely immune to spacecraft.
We can only briefly understand its arid landscape from these two perspectives Russia landing Reached the surface of Venus in the 1980s. So, not surprisingly, Natural astronomy The upper part of the atmosphere of Venus contains a molecule that may be a sign of life, which is considered a kind of Shock.
Its presence in the earth’s atmosphere is very small, less than a few parts per trillion, because it is quickly destroyed by the following processes: oxidation. However, the fact that this molecule exists in our oxidizing atmosphere is due to the fact that it is continuously produced by microorganisms. Therefore, it is proposed that phosphine in the atmosphere of rocky planets is a solid signal of life.
It should not be stable in the atmosphere of a planet like Venus, otherwise it will quickly rust unless there is a constant supply of freshness, as it does on Earth. So why did the study authors look for phosphine in such a hopeless environment? Are you sure you found it?
When reading between the lines of the report, it seemed that the team did not expect to find phosphine. In fact, they seem to be actively seeking his absence. Venus provides the “basic atmosphere” of a rocky planet without the biological characteristics of phosphine. Scientists who study rocky exoplanets can compare the atmosphere of these objects with that of Venus to identify any possible phosphine biological characteristics.
Therefore, it is somewhat surprising to find that the global concentration of this molecule is about 1,000 times that of the earth. In fact, he asked the author to perform one of the most detailed forensic dissections of his data, which I have ever seen.
The first data set was obtained using the James Clerk Maxwell Telescope (JCMT) in Hawaii in June 2017, clearly showing the presence of phosphine, and the second data set was recorded on another instrument using a different telescope.
These observations were made in March 2019 with a higher spectral resolution, using Atacama Large Millimeter Wave Array(ALMA) in Chile. The two data sets are almost indistinguishable. Phosphine exists in the atmosphere of Venus and is irregularly distributed at mid-latitudes, decreasing towards the poles.
But where did it come from? The raw material of phosphine is phosphorus, which is a well-known chemical element that can support many possible chemical reactions. The Vega probe (from the former Soviet Union) was used to measure the phosphorus in the atmosphere of Venus and found that it exists in the form of oxidized molecules P₄O₄.
In trying to explain the existence of phosphine, astronomers Jan GreavesResearchers from Cardiff University and his team used Vega data and modeled nearly 100 different chemical reactions in the atmosphere to see if they can reproduce what they found的phosphine.
Although tested under varying conditions (pressure, temperature, reagent concentration), they found that none of them was feasible. They even considered underground reactions, but Venus must have at least twice the volcanic activity of Earth to produce enough phosphine in this way.
What about meteors that carry matter to Venus? They also considered this, but found that it does not allow the phosphine content indicated by the data. In addition, there is no evidence that significant recent impacts may increase the concentration of phosphorus in the atmosphere. The research team also considered whether the reaction with lightning or solar wind would generate phosphine in the atmosphere, but found that this method can only produce negligible amounts.
Where shall we leave? The concentration of phosphine in the atmosphere of Venus is much higher than the concentration that can be explained by non-biological processes. Does this mean that there are microorganisms in the atmosphere of Venus, passing through the clouds in the aerosol droplets with tiny Venus fly traps?
Evidence of life? Only “abnormal and inexplicable chemistry”
The author did not claim to have found evidence of life, just “abnormal and inexplicable chemical reactions”. But, as Sherlock Holmes said to Dr. Watson: “Once the impossible is eliminated, then no matter how impossible it is, it is still a fact.”
The existence of methane as a biological signal in the Martian atmosphere still causes intense debate.Perhaps astrobiologists who are looking for life beyond Earth now have additional atmospheric biological signals About what to discuss.
The European Space Agency is consider A visit to Venus is currently underway, and it will determine its geological and tectonic history, including observation of possible volcanic gas. This will give you a better understanding of the compounds in the atmosphere of Venus. New research should advance this task.
Original article in conversation.
Monica Grady She works at the Open University, is the president of Liverpool Hope University and the principal researcher of the Natural History Museum. It has received funding from STFC and the British Space Agency.