NASA’s planetary science program is making a big bet on Venus, after decades of putting its chips on Mars in the search for hints of past or present life out there in the solar system.
The bet comes in the form of a double dose of development funding for Discovery Program missions, amounting to as much as $1 billion. Both DAVINCI+ and VERITAS were selected from a field of four finalists in a competitive process — leaving behind missions aimed at studying Jupiter’s moon Io and Neptune’s moon Triton.
“These two sister missions are both aimed to understand how Venus became an inferno-like world capable of melting lead at the surface,” NASA Administrator Bill Nelson said today in his first “State of NASA” address. “They will offer the entire science community the chance to investigate a planet we haven’t been to in more than 30 years.”
Lessons from Venus, which underwent a runaway greenhouse effect early in its existence, could improve scientists’ understanding of our own planet’s changing climate. The missions could also address one of the biggest questions about the second rock from the sun: whether life could exist in the upper reaches of its cloud layer.
The study could lead to a range of concepts for space missions to Venus, adding to several proposals that are already under consideration by NASA and other space agencies.
MIT planetary scientist Sara Seager, one of the authors of the research paper published this week in Nature Astronomy, is leading the Breakthrough Initiatives’ project as principal investigator. There’s already a website devoted to the study, VenusCloudLife.com, and a virtual kickoff meeting is set for Sept. 18, she told me today.
Among other leaders of the Venus Life Finder Mission Concept Study are MIT’s Janusz Petkowski and William Bains, two of the co-authors of the Nature Astronomy study; Georgia Tech’s Chris Carr; Caltech’s Bethany Ehlmann; the Planetary Science Institute’s David Grinspoon; and Pete Klupar, chief engineer of the Breakthrough Initiatives.
The study group will follow up on findings suggesting that a biomarker known as phosphine or PH3 is present within a potentially habitable band of clouds surrounding the hellishly hot planet. Phosphine can be produced by non-biological processes, but the team behind this week’s published findings said they could not explain how it was present at the detected levels unless biology was involved.
For decades, scientists have debated whether life might exist in the clouds of Venus — specifically, within a layer that’s between 30 and 40 miles above the surface. That’s the only place in the planet’s environment where water could exist in liquid form, and even there, the atmosphere contains droplets of highly corrosive sulfuric acid. Finding life is a long shot, but it’s a shot Milner thinks is worth taking.
“Finding life anywhere beyond Earth would be truly momentous,” Milner said in a news release. “And if there’s a non-negligible chance that it’s right next door on Venus, exploring that possibility is an urgent priority for our civilization.”
The budget for the Venus mission concept study is nowhere near $100 million. Seager said via email that the study will get a “few hundred thousand” dollars in support from the Breakthrough Initiatives, and that “we aim to have ‘in-kind’ contributions, i.e., work contributed, that push that number much higher.”
“It’s not really a huge amount for mission studies, but we are leveraging the formal study to get lots of people from the community to contribute,” she explained during a separate phone conversation. “We’ve got scientists, engineers, and we also have some industrial partners joining … but the study is just starting.”
Seager said Rocket Lab’s plan would be classified as a small mission concept. Such a concept envisions having a cruise vehicle drop off a descent capsule with a few kilograms’ worth of scientific instruments. The instruments would analyze Venus’ atmospheric composition for up to 10 minutes, potentially confirming the presence of phosphine and looking for other chemical signs of life.
Medium mission concepts would involve sending an inflatable balloon to Venus on a bigger rocket as a piggyback payload. The mission would be similar to what the Soviets did in the 1980s when they sent balloon-borne instruments into the Venusian atmosphere. Those probes transmitted data for a couple of days before their batteries gave out.
Such missions could accommodate an arsenal of scientific instruments amounting to as much as 20 kilograms (44 pounds).
“They could go beyond just detecting gases,” Seager told me. “They could analyze the liquid droplets in Venus’ atmosphere. They could try to identify complex molecules, like heavier molecules of the types that are only associated with life. And we’d like to imagine having a microscope on board. We could collect droplets and concentrate them and see if there’s anything that might resemble any kinds of life.”
Large mission concepts would involve sending an orbiter as well as a long-lasting balloon platform to Venus for months of study.
Seager said she expects the Breakthrough Initiatives project to work in a collaborative fashion with other teams that have parallel proposals for missions to Venus.
Among the potential missions are DAVINCI+, which aims to send a probe through Venus’ clouds; and VERITAS, which is designed to map Venus’ geology. Those mission concepts are among four finalists in NASA’s Discovery Program, along with concepts for missions to the Jovian moon Io and the Neptunian moon Triton. One or two of the concepts are to be selected for further funding next year.
“There is no doubt that NASA’s Science Mission Directorate will have a tough time evaluating and selecting from among these very compelling targets and missions, but I know the process will be fair and unbiased,” NASA Administrator Jim Bridenstine said this week.
But wait, there’s more: Plans for a NASA-led Venus Flagship Mission have been under discussion for years, and NASA is currently talking with the European Space Agency about an ambitious Venus mission concept called EnVision. Meanwhile, space scientists in Russia, India and China have their own ideas for missions to Venus.
A decade ago, the European Space Agency considered sending a balloon to Venus as part of a proposed mission called the European Venus Explorer, or EVE. That proposal fizzled out, but a different mission with a European connection, BepiColombo, should get a close-up look at Venus next month while on its way to Mercury.
Scientists say they’ve detected a chemical associated with biological activity within the clouds of Venus, at a height where airborne life forms could theoretically exist.
The chemical, known as PH3 or phosphine, isn’t the first biomarker to be found in Venus’ atmosphere. But the scientists say they can’t come up with a non-biological process that could produce phosphine at the levels they’re seeing.
This isn’t the smoking gun for life on Venus. Nevertheless, the latest findings — which leaked out over the weekend and were published today in Nature Astronomy — give peer-reviewed weight to an idea that once seemed almost ludicrous: the idea that microbes or other life forms may be perpetually floating in Venus’ acidic air, more than 30 miles above the planet’s searingly hot surface.
The findings are also likely to give a push to several proposed space missions that are already targeting the clouds of Venus.
“It may be that Venus, not Mars, is our best hope for a long-inhabited nearby neighbor,” David Grinspoon, a senior scientist at the Planetary Science Instutute, told me in an email.
The possibility of finding life in Venus’ clouds has been under debate for decades. The late astronomer Carl Sagan surveyed the prospects almost 60 years ago. More recently, Grinspoon and other astrobiologists have revived the case for closer study of Venus, in hopes of finding traces of microbial life in the clouds.
Grinspoon told me it’s been a tough sell. “Folks would roll their eyes at my conference talks, but I was tolerated because I did a lot of good work on other aspects of Venus, writing papers on the clouds, the surface evolution, the climate, and so forth,” he said.
Venus’ dense, surface-obscuring atmosphere consists primarily of carbon dioxide, but it’s also laced with droplets of sulfuric acid that makes it inhospitable to most life on Earth.
Even if amped-up versions of our own planet’s acid-loving microbes were to exist on Venus, the only place astrobiologists can imagine them getting a foothold would be within a temperate band of clouds that lie between 30 and 40 miles above the surface.
Just last month, a team of scientists — including some of the co-authors of the newly published study — proposed a spore-based life cycle for aerial microbes within that cloud band.
What kind of evidence might such creatures leave behind? Researchers at the Massachusetts Institute of Technology zeroed in on phosphine — a smelly, toxic gas given off by anaerobic bacteria on Earth. MIT planetary scientist Clara Sousa-Silva thought the spectral fingerprint of phosphine would be a good biosignature to look for when advanced telescopes analyze the light reflected by planets in alien star systems.
“I was thinking really far, many parsecs away, and really not thinking literally the nearest planet to us,” she said in a news release.
The astronomers who focused in on Venus weren’t expecting to find phosphine, either. When they observed the planet using the James Clerk Maxwell Telescope in Hawaii, they expected to rule out some of the claims surrounding life on Venus.
“This was an experiment made out of pure curiosity, really — taking advantage of JCMT’s powerful technology, and thinking about future instruments,” study lead author Jane Greaves, an astronomer at Cardiff University in Wales, said in a news release.
“I thought we’d just be able to rule out extreme scenarios, like the clouds being stuffed with organisms,” she said. “When we got the first hints of phosphine in Venus’ spectrum, it was a shock!”
What’s more, the phosphine was found precisely in the band of the cloud layer that’s most hospitable to life.
The detection was confirmed with follow-up observations from the Atacama Large Millimeter Array, or ALMA, in Chile. Greaves and her team then turned to other scientists to help interpret the findings.
Researchers considered a wide range of non-biological mechanisms for putting phosphine into the Venusian atmosphere — for example, by cooking other molecules with solar radiation or lightning, or having the wind sweep up minerals from the surface, or having the phosphine expelled by volcanoes, or bringing it in from space via meteors.
Phosphine is created non-biologically at Jupiter and Saturn, due to the abundance of hydrogen and the crushing atmospheric pressure at those gas giants, but the researchers noted that such conditions don’t exist on Venus. “That particular chemistry is definitely not happening at Venus,” MIT’s William Bains said today during a news briefing.
None of the mechanisms that the researchers considered could produce the level of phosphine that the astronomers detected, which amounts to 20 molecules per billion. Their most productive non-biological scenario could make, at most, only one-ten-thousandth of the required amount.
That leaves the biological scenario as the favored explanation, unless someone else comes up with a better explanation that the research team missed.
“It’s very hard to prove a negative,” Sousa-Silva said. “Now, astronomers will think of all the ways to justify phosphine without life, and I welcome that. Please do, because we are at the end of our possibilities to show abiotic processes that can make phosphine.”
“A long time ago, Venus is thought to have oceans, and was probably habitable like Earth,” she said. “As Venus because 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.”
So what’s next? Sousa-Silva and MIT’s Jason Dittman are leading an effort to confirm the phosphine findings with data from other telescopes, and map the distribution of phosphine across the Venusian atmosphere over time. If there are daily or seasonal variations, that could provide additional evidence for biological activity.
“The experiment must and will be repeated,” Grinspoon told me. “Laboratory studies will be undertaken to see how PH3 behaves in a Venus-like environment and what else could possibly produce it. But the best test, and the one I’m most excited about, is to go back to Venus and investigate the atmosphere in situ.”
Last month, a panel of scientists presented a 222-page report laying out the possibilities for a flagship mission to Venus, as part of the astronomy community’s 2020 decadal survey of science priorities.
Another concept, known as DAVINCI+, is one of four proposals vying for funding through NASA’s Discovery Program. The DAVINCI+ spacecraft would map Venus and its atmosphere from orbit. It’d also drop a spherical probe through the atmosphere, all the way to the surface, to sniff out the molecules making up each layer.
“Our vision for DAVINCI+ is to send a chemistry lab and orbiter to Venus to put the planet into its appropriate context in our solar system,” principal investigator Jim Garvin, who is chief scientist at NASA’s Goddard Space Flight Center, said in a news release.
If DAVINCI+ is selected for full funding next year, Garvin and his teammates propose launching the mission in 2026.
Meanwhile, California-based Rocket Lab is making plans to send a probe to Venus within three years or so.
“I’m working very hard to put together a private mission to go to Venus in 2023,” Rocket Lab CEO Peter Beck said last month during a webcast. “We’re going to learn a lot on the way there, and we’re going to have a crack at seeing if we can discover what’s in that atmospheric zone. And who knows? You may hit the jackpot.”
MIT’s Sara Seager said she and her colleagues have been talking with Rocket Lab about putting together the scientific payload for such a mission. The requirements are challenging: Such a payload would have to weigh no more than 3 kilograms (6.6 pounds), Seager said.
Details about potential funding for Rocket Lab’s mission haven’t yet come to light, but Russian-Israeli tech billionaire Yuri Milner is known to have Venus on his short list for a privately funded mission.
Back in 1985, the twin Soviet Vega probes deployed two balloon explorers in the Venusian atmosphere. Instruments on the balloons sent back data for 46 hours before their batteries ran out. Today, Seager was asked about that mission concept and said “a balloon is certainly the best way” to study what’s in the clouds.
“We have a long list of things we’d like, actually,” she said.
“Now that we’ve found a genuine candidate biosignature, we absolutely must go,” he said. “And even if this turns out to be a false alarm, it could be productive, in the way that the ‘Mars rock’ (ALH84001) was. That turned out — probably — to be a false alarm, but it got everyone to think about it in a fresh way and ask, ‘Why not?’ ”
Update for 8:50 a.m. PT Sept. 14: NASA’s associate administrator for science, Thomas Zurbuchen, tweeted that the findings are “intriguing” but added that NASA will defer further comment until the post-publication discussion has run its course:
An intriguing paper about chemistry on Venus was published today. @NASA was not involved in the research & cannot comment directly on the findings; however, we trust in the scientific peer review process & look forward to the robust discussion that will follow its publication. https://t.co/uA0QztrAnV
Update for 1:10 p.m. PT Sept. 14: Later in the day, NASA Administrator Jim Bridenstine tweeted that “it’s time to prioritize Venus” — which will probably lift the spirits of the folks working on the aforementioned proposals for missions to Venus:
Life on Venus? The discovery of phosphine, a byproduct of anaerobic biology, is the most significant development yet in building the case for life off Earth. About 10 years ago NASA discovered microbial life at 120,000ft in Earth’s upper atmosphere. It’s time to prioritize Venus. https://t.co/hm8TOEQ9es
In addition to Greaves, Sousa-Silva, Bains and Seager, the authors of the Nature Astronomy paper, “Phosphine Gas in the Cloud Decks of Venus,” include Anita Richards, Paul Rimmer, Hideo Sagawa, David Clements, Janusz Petkowski, Sukrit Ranjan, Emily Drabek-Maunder, Helen Fraser, Annabel Cartwright, Ingo Mueller-Wodarg, Zhuchang Zhan, Per Friberg, Iain Coulson, E’lisa Lee and Jim Hoge.
The computer modeling wound the clock back on Venus’ climate, using calculations similar to those employed to wind the clock forward for our own planet’s climate.
“Many of the same tools we use to model climate change on Earth can be adapted to study climates on other planets, both past and present,” lead study author Michael Way, a researcher at the Goddard Institute, said in a NASA news release. “These results show ancient Venus may have been a very different place than it is today.”
For months, scientists have puzzled over weirdly bright spots of material shining on the asteroid Ceres, but now they say the spots are probably made of salty ice.
That determination, based on a detailed analysis of spectral data from NASA’s Dawn orbiter, comes in a paper published today by the journal Nature. Dawn’s images highlight one particular patch in a 106-mile-wide impact basin known as Occator Crater, but other spots are spread across the surface of the 590-mile-wide dwarf planet.
“The global nature of Ceres’ bright spots suggests that this world has a subsurface layer that contains briny water-ice,” the study’s principal author, Andreas Nathues of the Max Planck Institute for Solar System Research, said in a NASA statement. He and his co-authors suggest that cosmic impacts dig up enough surface material to expose the shiny ice.