Phosphine molecules have been detected in the planet’s clouds and may indicate the existence of microbial life.
Phosphine molecules, a substance strongly associated with life as we know it, were discovered in the atmosphere of Venus, according to a study recently published in the journal Nature Astronomy.
The study was led by scientists from Cardiff University, in the UK, and MIT, in the US, as well as researchers from several other institutions around the world.
According to the current scientific model, phosphine can only arise from two processes.
The first is industrial activity, which generates the substance as a product.
The second is the metabolism of anaerobic microorganisms, which absorb phosphate from minerals or biological material, add hydrogen and, then, release phosphine.
“This means either this is life, or it’s some sort of physical or chemical process that we do not expect to happen on rocky planets,” said co-author Janusz Petkowski, who works at the MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).
The researchers made the detection using data from the James Clerk Maxwell Telescope (JCMT), in Hawaii, and the Atacama Large Millimeter Array (ALMA) observatory, in Chile.
After a series of calculations, they estimated that the concentration of phosphine in the clouds of Venus is low, only about 20 molecules in every billion.
A fascinating surprise
Initially, the researchers thought that this amount of phosphine could come from natural non-biological processes on the planet, such as volcanic eruptions or electrical discharges caused by lightning.
However, it was found that these non-biological sources produce a maximum of one ten-thousandth of the amount of phosphine that has been observed.
On the other hand, to create the observed amount of phosphine on Venus, terrestrial microorganisms would only need to work at about 10% of their maximum capacity.
“Now, astronomers will think of all the ways to justify phosphine without life, and I welcome that,” said Clara Sousa-Silva, who also works at the EAPS. “Please do, because we are at the end of our possibilities to show abiotic processes that can make phosphine.”
Something completely new
This finding has implications not only for astronomy, but also for other fields. The discovery is particularly interesting because it indicates that, without doubt, something new has been observed: either an unprecedented process in chemistry and physics, or the existence of extraterrestrial life.
Although the discovery of phosphine in the clouds of Venus came as a surprise, the researchers are confident of the accuracy of the detection, as the data was collected when ALMA was at a good angle of observation.
“In the end, we found that both observatories had seen the same thing — faint absorption at the right wavelength to be phosphine gas, where the molecules are backlit by the warmer clouds below,” said lead author Jane Greaves, from the Cardiff University, UK.
A hostile world
Venus and Earth are considered similar planets when it comes to size, mass, and surface composition. Also, both planets have an atmosphere and a weather system, which is why some people think Venus is the ideal terraforming candidate (at least in the Solar System).
However, there are some crucial differences between the two. The main one is atmospheric composition.
Venus’ atmosphere is toxic and heavy, made up almost entirely of thick clouds of carbon dioxide, and the surface temperature can easily exceed 400 degrees Celsius.
The conditions there are so extreme that the only probes sent to the surface of Venus by the Soviet Union between the 1960s and 1980s were literally melted and crushed by the unbearable atmospheric pressure.
A Venusian oasis
There is, however, a cloud deck in the atmosphere of Venus, between 48 and 60 kilometers (30 and 37 mi) above the surface, where temperatures range from -1 to 93 degrees Celsius – and this is precisely where phosphine was found.
“This phosphine signal is perfectly positioned where others have conjectured the area could be habitable,” Petkowski said.
If there is, in fact, life in the clouds of Venus, scientists hypothesize that it is an aerial form, found only in the cloud deck, in which boiling volcanic activity has little influence.
According to Sousa-Silva, it is believed that, long ago, Venus had oceans and was probably habitable like Earth, characteristics that have changed a lot in the last thousands of years.
“As Venus became less hospitable, life would have had to adapt, and they could now be in this narrow envelope of the atmosphere where they can still survive,” Sousa-Silva said.
“This could show that even a planet at the edge of the habitable zone could have an atmosphere with a local aerial habitable envelope.”
Meanwhile, Sara Seager and Petkowski explore the possibility that the lower layers of Venus’ atmosphere, just below the cloud deck, could be crucial for the survival of a hypothetical Venusian biosphere.
As they explain, there may be a cycle that keeps the hypothetical organism in the clouds perpetually.
Petkowski points out, however, that any life in the atmosphere of Venus would be fundamentally different from life as we know it.
“The liquid medium on Venus is not water, as it is on Earth,” he explained.
Now the team hopes to map the presence of the molecule in the atmosphere of Venus, to see if there are daily or seasonal variations in the concentration of phosphine.
“Technically, biomolecules have been found in Venus’ atmosphere before, but these molecules are also associated with a thousand things other than life,” Sousa-Silva said.
“The reason phosphine is special is, without life it is very difficult to make phosphine on rocky planets. Earth has been the only terrestrial planet where we have found phosphine, because there is life here.”
This discovery promises to change astronomy, and continuing to observe the long-overlooked Venus is essential, as well as planning new space missions to the planet.
Until now, Venus was considered a dead planet. This discovery will rekindle debates and studies, which will need to be revised because of this new data.