Researchers believe that there could be potential lifeforms producing ammonia in the clouds of Venus that are “very unlike anything we’ve seen”.
The colourless gas, a compound of nitrogen and hydrogen, could be indicative of chemical reactions that would make the planet – 47.34 million kilometres from Earth – more habitable to alien life.
On our planet, ammonia is a common left-over waste from aquatic organisms. Its presence in Venus’ upper atmosphere has been puzzling astronomers since the 1970s – with scientists believing that it should not be produced by any known force on the world.
Venus itself is so hot that it is inconceivable to have life forms, and if there is life in the clouds it is likely to be microbes like Earth bacteria – albeit with a chemical composition unlike that we have seen on our planet, or even neighbouring planets like Mars.
This is because life on Mars is more likely to be similar to that on Earth and so scientists have a greater idea of what to expect. Venus, in contrast, is unlike any other planet in the solar system.
In a new study, researchers from Cardiff University, MIT and Cambridge University modelled a set of chemical processes to show that – if ammonia is indeed present – it would set off a cascade of chemical reactions that would neutralize surrounding droplets of sulfuric acid.
If this happened, it would increase the acidity of the clouds from -11 to zero; on the pH scale this remains incredibly acidic, but it would be at a level that life could tolerate. On Earth there are lifeforms that produce ammonia to neutralize their challenging environment.
“We know that life can grow in acid environments on Earth, but nothing as acid as the clouds of Venus were believed to be. But if something is making ammonia in the clouds, then that will neutralize some of the droplets, making them potentially more habitable,” said co-author of the study Dr William Bains, from Cardiff University’s School of Physics and Astronomy.
The scientists go as far to propose that the most plausible explanation is that the origins of the ammonia is biological, rather than natural forces such as lightning or volcanic eruptions.
As for the source of ammonia itself, the authors propose the most plausible explanation is of biological origin, rather than any non-biological source such as lightning or volcanic eruptions.
“Ammonia shouldn’t be on Venus,” said study co-author Professor Sara Seager, from MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “It has hydrogen attached to it, and there’s very little hydrogen around. Any gas that doesn’t belong in the context of its environment is automatically suspicious for being made by life.”
Some chemical signatures in the clouds had gone unexplained for decades: the presence of oxygen; non-spherical particles; and unexpected levels of water vapor and sulphur dioxide.
It was thought this could be explained by dust – perhaps minerals swept up from Venus’ surface made their way into the clouds and interact with sulphuric acid. The issue, however, was that the amount of dust necessary for this to be true was far too massive.
If life were producing ammonia, however, the chemical reaction would naturally produce oxygen. The ammonia would then dissolve in the acid, transforming from a round, liquid shape into a “salt-like slurry”.
“There are many other challenges for life to overcome if it is to live in the clouds of Venus,” said Bains. “There is almost no water there for a start, and all life that we know of needs water. But if life is there, then neutralizing the acid will make the clouds just a bit more habitable than we thought.”
The chances of life being present on Venus is very small, Dr Bains said, who remains skeptical that these issues could be explained by extraterrestrials. This could come, however, from the vast disparity life on Venus could have compared to life on Earth as well as the sheer scale of the possibility of alien life.
“Having said that, if there’s even a small chance there’s life there it will such an epoch-changing discover that it’s really worth following up”.
In 2023 the Venus Life Finder mission will launch to study cloud particles, but the detection of alien life will take time. Sending hardware to Venus is challenging and expensive, with the final goal to retrieve a sample that could potentially contain life and return it to Earth for vastly greater study than could be conducted remotely.
Dr Bains predicts that such a study – and sampling – could happen before the end of the decade, but is more likely to take place before 2040.
This is not the first time that the discovery of a chemical has given hints that there might be extraterrestrial life on Venus. Last year, scientists from Cardiff University also found traces of phosphine, a rare and toxic gas, in the atmosphere.
Much like ammonia, phosphane is a strong biosignature. "Either phosphine is produced by some sort of chemical or geological process that no one knows about – or there could be a biological reason," said Emily Drabek-Maunder, an astrophysicist from the Royal Observatory Greenwich, said at the time. However, three later studies called this into question – detecting no signs of phosphane in the Venusian atmosphere.
This research has not yet reached that stage, only suggesting an explanation for these strange phenomena; it will not be until further radio telescope examination that scientists might come to more concrete solutions.
