The search for life beyond the earth has revolved largely around our rocky red neighbor. NASA has launched a number of rovers over the past few years, currently along a new route that passes through the dusty surface of Mars to signal water and other signs of habitat.
Now, in a surprising twist, scientists from MIT, Cardiff University and elsewhere have seen what signs of life may be in the clouds of our other, even closer planetary neighbor, Venus. While they have not found direct evidence of living organisms there, if their observation is indeed linked to life, it must be some sort of “aerial” life-form in the clouds of Venus – which is otherwise a scorched and inhumane. world. His discovery and analysis is published today in the journal Nature astronomy.
Astronomers, led by Jane Greaves of Cardiff University, detected a spectral fingerprint, or light-based signature, of phosphine in Venus’s atmosphere. Scientists at MIT have previously shown that if this smelly, poisonous gas is ever detected on a stony, terrestrial planet, it can only be produced by a living organism. Researchers detected this using the James Clerk Maxwell Telescope (JCMT) in Hawaii and the Atacama Large Millimeter Array (ALMA) Observatory in Chile.
The MIT team followed the new observation with a detailed analysis to see if anything other than life could produce phosphine in the harsh, sulfuric environment of Venus. Based on the many scenarios they considered, the team concludes that apart from the presence of life, there is no explanation for the phosphine found in Venus’ clouds.
“It’s very difficult to prove a negative,” says research scientist Clara Susa-Silva of MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “Now, astronomers will think of all the ways to justify phosphine without life, and I welcome it. Please do, because we are at the end of our possibilities to show abiotic processes that can make phosphine. ”
“It means that either this is life, or it’s some kind of physical or chemical process that we don’t expect to happen on rocky planets,” says Janusz Petkowski, co-author and EAPS research scientist.
Other MIT co-authors include William Bains, Sukrit Ranjan, Xuchang Zhan and Sarah Seeger, who are professors of planetary science in 1941, with colleagues at Cardiff University, with appointments in the departments of Physics and Aeronautics and Astronautics. University of Manchester, University of Cambridge, MRC Laboratory of Molecular Biology, Kyoto Sangyo University, Imperial College, Royal Observatory Greenwich, Open University and East Asian Observatory.
Looking for foreign things
Venus is often referred to as Earth’s twin, as neighboring planets are similar in their size, mass, and rocky composition. They also have significant atmospheres, although this is where their similarities end. Where the Earth is a world of temperate oceans and lakes, the surface of Venus is a boiling hot landscape, where temperatures reach 900 degrees Fahrenheit and a strong wind that dries up compared to the driest places on Earth.
Most of the planet’s atmosphere is also highly inhumane, prone to dense clouds of sulfuric acid, and cloud droplets that are billion times more acidic than most acidic environments on Earth. The atmosphere lacks nutrients that are abundantly present on the surface of a planet.
“Venus is a very challenging environment for any kind of life,” Seeger says.
However, Venus has a narrow, temperate strip within the atmosphere, 48 and 60 kilometers above the surface, with temperatures ranging from 30 to 200 degrees Fahrenheit. Scientists have speculated, with much controversy, that if life exists on Venus, then this layer of the atmosphere, or cloud deck, is probably the only place where it will survive. And it just so happens that this cloud deck is where the team saw signs of phosphine.
“This phosphine signal is fully deployed where others have speculated that the area may be habitable,” says Petkowski.
This was first detected by Greaves and his team, who zeroed in on the use of JCMT on the Venus atmosphere to pattern light that could indicate the presence of unexpected molecules and a possible signature of life. When he picked up a pattern that indicated the presence of phosphine, he approached Susa-Silva, who has spent the bulk of his career to characterize the smelly, toxic molecule.
Susa-Silva initially believed that astronomers could discover phosphine as a biosphere on very distant planets. “I was really thinking too far, many farther away, and not really literally thinking of the nearest planet to us.”
The team followed Greaves’ initial observations using the more sensitive ALMA Observatory with the help of Anita Richards of the ALMA Regional Center at the University of Manchester. Those observations confirmed that what Greaves saw was actually a pattern of light that matched that Venus’s clouds would emit phosphine gas.
The researchers then used a model of the Venusian atmosphere developed by Hideo Sagawa of Kyoto Sangyo University to interpret the data. They found that phosphine on Venus is a minor gas, present at a concentration in about 20 of every billion molecules in the atmosphere. Although this concentration is low, researchers point out that the phosphine produced by life on Earth can be found in even lower concentrations in the atmosphere.
The MIT team, led by Bains and Petkowski, used computer models to explore all possible chemical and physical paths associated with life, which could produce phosphine in the harsh environment of Venus. Bains considered various scenarios, which could produce phosphine in the form of sunlight, surface minerals, volcanic activity, a meteor strike, and lightning. Ranjan collaborated with Paul Rimmer of the University of Cambridge to explain how phosphine can be produced in Venus clouds through these mechanisms. In each scenario, they believed that the phosphine produced would amount to only a small fraction of what the new observations on Venus’ clouds suggest.
“We’ve actually gone through all the possible paths that can produce phosphine on a rocky planet,” says Petkowski. “If it is not life, then our understanding of rocky planets is severely lacking.”
A life in the clouds
If there is indeed life in Venus’ clouds, researchers believe it to be a celestial form, only present in the temperate cloud deck of Venus, far above the boiling, volcanic surface.
“A long time ago, Venus is considered for the oceans, and was probably habitable like the Earth,” Susa-Silva says. “As Venus became less hospitable, life had to adapt, and they could now be in the narrow envelope of this environment where they could still live. It can show that a planet at the edge of a habitable zone can also be an atmosphere with a local air-habitable envelope. ”
In a separate line of research, Seeger and Petkowski explore the possibility that the lower layers of Venus’ atmosphere, just below the cloud deck, may be important for the existence of an imaginary Venusian biosphere.
“You can, in principle, have a life cycle that maintains life in the clouds,” says Petkowski. “The liquid medium on Venus is not water, as it is on Earth.”
Sousa-Silva is now trying out with Jason Dittman at MIT to confirm the detection of phosphine with other telescopes. They are also expected to map the presence of the molecule in Venus’s atmosphere to see if there are diurnal or seasonal changes in the signal that would suggest life-related activity.
Susa-Silva says, “Technically, biomolecules have been found in Venus’s atmosphere before, but these molecules are also associated with a thousand things.” “Phosphine is a special cause, it is very difficult to make phosphine on rocky planets without life. Earth is the only terrestrial planet where we have found phosphine, because there is life here. till now.”
The research was funded by the Council for Science and Technology Facilities, European Southern Observatory, Japan Society for the Promotion of Science, Heising-Simmons Foundation, Change Happens Foundation, Simmons Foundation, and Horizon of the European Union. 2020 Research and Innovation Program.