The search for life outside Earth has largely centered around our rocky red neighbor. NASA has launched several rovers over the years. With a new one currently on the way, To sift the dusty surface of Mars for signs of water and other signs of habitability.

Now, in a surprising twist, scientists at Massachusetts Institute of Technology, Cardiff University and elsewhere have observed what could be signs of life in the clouds of Venus, our closest planetary neighbor. Although they did not find direct evidence of living organisms there, if their observation was actually related to life, it must have been some kind of “air” life in the clouds of Venus – the only habitable part of what is otherwise a scorched and inhospitable area. Globalism. Their discovery and analysis are published today in the journal Natural Astronomy.

Astronomers, led by Jane Graves of Cardiff University, discovered in Venus’ atmosphere a spectral signature, or light signature, Phosphine. Massachusetts Institute of Technology scientists previously showed that if this stinky, toxic gas was discovered on a rocky Earth planet, it could only be produced by an organism there. Researchers made the discovery with the James Clerk Maxwell Telescope (JCMT) in Hawaii, and the Atacama Large-Millimeter Array Observatory (ALMA) in Chile.

The MIT team followed up on the new observation with a comprehensive analysis to see if anything other than life could produce phosphine in the harsh, sulfurous environment of Venus. Based on the many scenarios they considered, the team concluded that other than the existence of life, there is no explanation for phosphine detected in the clouds of Venus.

“It’s very difficult to prove negative,” says Clara Souza-Silva, a research scientist in the Division of Earth, Atmospheric and Planetary Sciences (EAPS) at the Massachusetts Institute of Technology. “Now, astronomers will think of all the ways to justify phosphine without life, and I welcome that. Please do, because we’re at the end of our possibilities to show the abiotic processes that can make phosphine.”

“This either means that this is life, or it is some kind of physical or chemical process that we do not expect to happen on rocky planets,” adds co-author and EAPS research scientist Janusz Petkovsky.

Other MIT co-authors include William Baines, Sukret Rangan, Zhuchang Zhan, and Sarah Seger, a 1941 professor of planetary science with appointments in the departments of Physics, Aeronautics and Astronautics, along with collaborators at Cardiff University, University of Manchester, University of Manchester. Cambridge, MRC Laboratory of Molecular Biology, Kyoto Sangyo University, Imperial College, Royal Greenwich Observatory, The Open University, and East Asia Observatory.

Searching for strange things

Venus is often referred to as Earth’s twin, as the neighboring planets are similar in size, mass, and rock composition. They also have important atmospheres, although this is where the similarities between them end. Where Earth is a habitable world of temperate oceans and lakes, the surface of Venus is a hot boiling landscape, with temperatures reaching 900 degrees Fahrenheit and stifling air that is drier than the driest places on Earth.

Much of the planet’s atmosphere is also somewhat inhospitable, being inundated with thick clouds of sulfuric acid and cloud droplets billions of times more acidic than the most acidic environment on Earth. The atmosphere also lacks the nutrients in abundance on the planet’s surface.

“Venus is a challenging environment for life of any kind,” says Seiger.

However, there is a narrow and temperate range within Venus’ atmosphere, between 48 and 60 kilometers above the surface, with temperatures ranging from 30 to 200 degrees Fahrenheit. Scientists have speculated, with much debate, that if life ever existed on Venus, then this layer of the atmosphere, or the surface of clouds, would likely be the only place it would live. And this cloud surface so happened to be where the team noticed the phosphine signals.

“This phosphine signal is positioned so perfectly that other people guess the area could be habitable,” says Petkovsky.

The discovery was first made by Greaves and her team, who used JCMT to focus on Venus’ atmosphere for patterns of light that could indicate the presence of unexpected particles and possible signatures of life. When she picked up a pattern indicating the presence of phosphine, she called Souza Silva, who has spent the bulk of her career describing the stinky poisonous molecule.

Souza Silva initially assumed that astronomers could search for phosphine as a biological classification on very distant planets. “I was thinking really far away, many parsecs, and in fact, literally not thinking of the planet closest to us.”

The team followed Graves’ initial observation using the more sensitive ALMA Observatory, with help from Anita Richards, of the Regional ALMA Center at the University of Manchester. These observations confirmed that what Graves observed was indeed a pattern of light that matches what phosphine would emit inside the clouds of Venus.

The researchers then used a Venusian envelope model, developed by Hideo Sagawa of Kyoto Sangyo University, to interpret the data. They found that phosphine on Venus is a secondary gas, present at a concentration of about 20 of every billion molecules in the atmosphere. Although this concentration is low, the researchers suggest that the phosphine produced by life on Earth can be found in lower concentrations in the atmosphere.

The MIT team, led by Bains and Petkowski, used computer models to explore all of the potential chemical and physical pathways unrelated to life that could produce phosphine in the harsh environment of Venus. Baines looked at various scenarios that could produce phosphine, such as sunlight, surface minerals, volcanic activity, meteor strike, and lightning. Then Ranjan and Paul Reimer of the University of Cambridge modeled how phosphine produced through these mechanisms could accumulate in flower clouds. In each scenario they looked at, the resulting phosphine would only reach a fraction of what new observations found on the clouds of Venus indicate.

“We’ve really gone through all the possible pathways that could produce phosphine on a rocky planet,” Petkovsky says. “If this is not the way life, then our understanding of rocky planets is sorely lacking.”

Life in the clouds

If there is indeed life in the clouds of Venus, researchers believe it is an atmospheric form, found only in the surface of the temperate clouds of Venus, well above the surface of boiling volcanic.

“A long time ago, Venus was thought to have oceans, and perhaps it was as habitable as the Earth,” Souza Silva says. “As Venus became less hospitable, life had to adapt, and they could now be in this narrow atmosphere where they could still survive. This could show that even a planet at the edge of the habitable zone can have an envelope. Habitable local air. “

In a separate line of research, Seager and Petkowski discovered the possibility that the lower layers of Venus’ atmosphere, just below the surface of the cloud, are essential for the survival of the hypothetical biosphere on Venus.

“You can, in principle, have a life cycle that always sustains life in the clouds,” says Petkovsky, who envisions any atmospheric Venusian life being fundamentally different from life on Earth. “The liquid medium on Venus is not water, as it is on Earth.”

Souza Silva is now leading an effort with Jason Detman at the Massachusetts Institute of Technology to confirm the discovery of phosphine using other telescopes. They also hope to map the molecule’s presence across Venus’ atmosphere, to see if there are daily or seasonal variations in the signal that would indicate activity related to life.

“Technically speaking, biomolecules have been found in Venus’ atmosphere before,” Souza Silva says. “But these particles are also associated with thousands of things other than life.” “The reason why phosphine is special is because without life it would be very difficult to make phosphine on rocky planets. Earth was the only terrestrial planet where we found phosphine, because there is life here. Until now.”

This research was funded, in part, by the Council of Science and Technology Facilities, European Southern Observatory, Japan Society for the Advancement of Science, Heising-Simons Foundation, Change Happens Foundation, Simons Foundation, and the European Union Horizon. 2020 Research and Innovation Program.