Life on Venus? It’s not as crazy as it sounds

Los Angeles Times - - FRONT PAGE - By Deb­o­rah Net­burn

In the search for life be­yond Earth, hu­mans have sent ro­bots to the rocky sur­face of Mars, de­ployed space­craft to in­ves­ti­gate the moons of Jupiter and Saturn and aimed their most pow­er­ful tele­scopes to­ward dis­tant so­lar sys­tems.

But now, in an un­ex­pected twist, a group of sci­en­tists say they have found pos­si­ble signs of ex­trater­res­trial life in a place where few had thought to look: high in the thick, toxic clouds of Venus, our clos­est plan­e­tary neigh­bor.

In that nox­ious en­vi­ron­ment, they dis­cov­ered a gas called phos­phine that is as­so­ci­ated with life on Earth.

The no­tion that the Venu­sian phos­phine could have been pro­duced by liv­ing or­gan­isms may seem ab­surd, the team mem­bers ac­knowl­edged. And yet it’s one of the most plau­si­ble the­o­ries they have.

“There are two pos­si­bil­i­ties for how it got there, and they are equally crazy,” said Mas­sachusetts Institute of Tech­nol­ogy as­tro­bi­ol­o­gist Sara Sea­ger, a mem­ber of the team that re­ported the dis­cov­ery Mon­day in the jour­nal Na­ture Astron­omy. “One sce­nario is it is some plan­e­tary process that we don’t know about. The other

is there is some life form liv­ing in the at­mos­phere of Venus.”

Sea­ger em­pha­sized that she and her col­leagues are not claim­ing to have found ev­i­dence of life on Venus. In­stead, they are say­ing they found a ro­bust sig­nal of a gas that doesn’t be­long in the planet’s at­mos­phere, and that it will take a lot more work to un­der­stand how it got there.

“What we need now is for the sci­en­tific com­mu­nity to come and tear this work to shreds,” said Clara Sousa-Silva, a molec­u­lar as­tro­physi­cist at MIT who worked on the pa­per. “As a sci­en­tist, I want to know where I went wrong.”

Phos­phine is a pyra­mid­shaped mol­e­cule with a phos­pho­rus atom on top and three hy­dro­gen atoms at the base. It is hard to make on rocky plan­ets like Earth and Venus be­cause it takes tremen­dous pres­sures and tem­per­a­tures to get the atoms to bond, Sousa-Silva said.

Those con­di­tions ex­ist deep within the in­te­rior of the gas gi­ants Jupiter and Saturn, but rocky plan­ets like Earth and Venus sim­ply don’t have the ther­mal en­vi­ron­ments that would al­low phos­phine to form spon­ta­neously.

On Earth, the pro­duc­tion of phos­phine is as­so­ci­ated with anaer­o­bic life, which does not need oxy­gen to sur­vive. It has been de­tected in marsh­lands, rice fields, sewage plants, an­i­mal fe­ces and the in­testi­nal tracts of fish and hu­man ba­bies, Sousa-Silva said.

Some­times it’s a byprod­uct of shoddy work in meth labs, and it has been used as a pes­ti­cide and an agent of war.

“I love phos­phine, but I would never want to be in a room with it,” Sousa-Silva said. “It is ex­tremely toxic. Very few peo­ple have smelled it and lived.”

Be­cause phos­phine is as­so­ci­ated with life on Earth, sci­en­tists such as Sea­ger and Sousa-Silva thought it might be a bio-sig­na­ture of life on other rocky plan­ets as well.

“I con­sid­ered a huge ar­ray of places we might look for phos­phine, but I never con­sid­ered look­ing next door,” Sousa-Silva said.

Al­though Venus is our clos­est neigh­bor, it has re­mained a pretty fringe place to look for signs of life. Its sur­face is un­in­hab­it­able for life as we know it, with tem­per­a­tures up to 900 de­grees Fahren­heit and bone-crush­ing at­mo­spheric pres­sure up to 90 times higher than that of Earth.

Sci­en­tists think Venus may have once had oceans of liq­uid wa­ter that boiled off at least 1 bil­lion years ago. To­day, the planet’s sur­face is far dryer than any­where on Earth, and its at­mos­phere con­sists mostly of car­bon diox­ide, with clouds of sul­phuric acid.

De­spite these hellish con­di­tions, a hand­ful of sci­en­tists since the 1960s have ar­gued that life could ex­ist in a re­gion 30 miles above the sur­face, where tem­per­a­tures and pres­sures are sim­i­lar to those on the Earth’s sur­face, and where small air­borne or­gan­isms could pos­si­bly sur­vive.

“It’s a very fer­tile en­vi­ron­ment,” said David Grin­spoon, an as­tro­bi­ol­o­gist and se­nior sci­en­tist with the Plan­e­tary Science Institute in Tuc­son, who was not in­volved in the study. “The cloud droplets pro­vide an aque­ous en­vi­ron­ment; there are nu­tri­ents and other el­e­ments you need for life and plenty of en­ergy sources.”

One po­ten­tial sce­nario is that life evolved on the sur­face when Venus still had oceans, then mi­grated to the clouds as the planet grew warmer over time. This life would likely be mi­cro­scopic and per­haps sim­i­lar to some forms of bac­te­ria that spend part of their lives in the ephemeral clouds on Earth.

Jane Greaves, an as­tronomer at Cardiff Univer­sity in Wales and lead au­thor of the new study, knew that the clouds of Venus had been sug­gested as a po­ten­tial habi­tat for life and that phos­phine could sig­nal the pres­ence of life on rocky plan­ets.

So she put two and two to­gether and set out to search for phos­phine in the small band of Venus’ at­mos­phere that just might be hab­it­able.

“I was specif­i­cally look­ing for signs of life,” she said.

Greaves is a ra­dio as­tronomer who had worked in the ’80s at Hawaii’s James Clerk Maxwell Te­le­scope. In early 2017, she called up Jes­sica Dempsey, the te­le­scope’s site di­rec­tor, and asked if she could do some­thing crazy. Then she pre­sented her plan.

“I said, ‘Of course!’ ” Dempsey said. “You are not go­ing to find what’s pos­si­ble if you don’t try the im­pos­si­ble.”

Greaves got a to­tal of eight hours of view­ing time over five morn­ings in June 2017, but it wasn’t un­til the end of 2018 that she was fi­nally able to take a close look at what the te­le­scope had seen.

It took sev­eral months to tease out a de­tec­tion of phos­phine from the noisy data, but even­tu­ally she found it.

Dempsey vividly re­mem­bers the day she re­ceived an email from Greaves with the de­tec­tion spec­tra.

“I just sat there, blink­ing at the screen,” said Dempsey, who wasn’t part of the study team. “When I re­gained the power of speech, I gave her a call and said, ‘You just blew my mind. Am I re­ally see­ing what I think I’m see­ing?’”

A sec­ond ob­ser­va­tion in March 2019 with the Ata­cama Large Mil­lime­ter/sub­mil­lime­ter Ar­ray in Chile con­firmed the dis­cov­ery.

Greaves’ next step was to find phos­phine ex­perts who could help her de­ter­mine whether the gas re­ally did rep­re­sent a po­ten­tial sign of life on Venus. A mu­tual friend led her to sci­en­tists at MIT.

“My first re­ply was, ‘Are you ab­so­lutely sure?’” said Sousa-Silva, who had re­cently writ­ten a pa­per ex­plain­ing why phos­phine could be a biosig­na­ture in ex­o­planet at­mos­pheres. “Be­cause it’s not just weird. It’s re­ally weird.”

Over the next sev­eral months, the MIT team ex­plored ev­ery chem­i­cal process they could think of that had the po­ten­tial to gen­er­ate phos­phine on Venus with­out the aid of life.

When they in­cor­po­rated lightning and me­teor strikes into their mod­els, they de­ter­mined that phos­phine could be pro­duced on Venus — but only in amounts that were a tiny frac­tion of what Greaves had found. Be­sides, phos­phine should de­grade in the at­mos­phere, but the steady amount sug­gests that it’s be­ing con­stantly re­plen­ished.

In des­per­a­tion, they con­sid­ered whether tec­tonic ac­tiv­ity might have driven the pro­duc­tion of the gas.

“We don’t even think that there are tec­ton­ics on Venus, but it still seems less crazy than aliens,” Sousa-Silva said.

Ul­ti­mately, they could not find a plau­si­ble ex­pla­na­tion for the pres­ence of phos­phine that did not in­volve some sort of life form.

But that doesn’t mean there isn’t one, said Matthew Pasek, an as­tro­bi­ol­o­gist at the Univer­sity of South Florida who was not in­volved in the work.

“It def­i­nitely bears fur­ther in­quiry,” he said. “My guess would be there is some non-bi­o­logic process that is mak­ing it, but they cer­tainly found some­thing weird.”

Pasek added that sci­en­tists still aren’t sure how life on Earth pro­duces phos­phine, or if it is made by or­gan­isms at all.

“We be­lieve it is bi­o­log­i­cal, but we don’t have proof of that yet,” he said.

The study’s au­thors agree that there is much more work to be done.

They hope their find­ings will in­spire more sci­en­tists to study phos­phine. They also hope to spend more time char­ac­ter­iz­ing the phos­phine on Venus to find clues about how it got there.

Send­ing a space­craft to Venus would be help­ful. NASA has two Venus mis­sions cur­rently un­der re­view.

But all of this will take time. It could take years or even decades to prove con­clu­sively whether there is life in the Venu­sian clouds, Sea­ger said.

“We have a long road ahead of us,” she said.

Ser­gio Otarola ESO

AS­TRONOMERS used Chile’s Ata­cama Large Mil­lime­ter/sub­mil­lime­ter Ar­ray to de­tect phos­phine, a gas as­so­ci­ated with life on Earth, in the clouds above Venus. “It’s not just weird,” one said. “It’s re­ally weird.”

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