An artist’s conception shows NASA’s Europa Clipper probe flying over Europa. (NASA / JPL-Caltech Illustration)
Scientists have verified that a method to look for cellular life on Europa, an ice-covered moon of Jupiter, just might work. The technique could be put to the test in the 2030s, when NASA’s Europa Clipper probe is due to make multiple flybys over the Jovian moon.
“It’s astonishing how the analysis of these tiny ice grains may tell us whether or not there is life on an icy moon. At least we now know that SUDA has these capabilities,” University of Washington planetary scientist Fabian Klenner told me in an email. Klenner is the lead author of a research paper about the process, published today in the open-access journal Science Advances.
SUDA will be capable of analyzing the chemical content of material that hits its detector, using a process called impact ionization mass spectrometry. The key feature of the process described by Klenner and his colleagues is that the analysis would be done on single ice grains, rather than on a blizzard of ice particles. That way, scientists can focus on individual grains that might hold a high concentration of the ingredients of a single cell.
At the time, their hypothesis was based on previously published research, computer modeling and lab experiments. But now the same scientists say they’ve found a shallow lake that just might fit the requirements — and it happens to be just a few hundred miles north of their home base in Seattle.
An artist's conception shows the exoplanet K2-18 b. (NASA / CSA / ESA / STScI / Cambridge U.)
Readings from NASA’s James Webb Space Telescope confirm the presence of carbon-based molecules including methane and carbon dioxide in the atmosphere of a distant planet known as K2-18 b — which supports previous suggestions that it might be the kind of ocean-covered world capable of harboring marine life.
K2-18 b, which was first detected in 2015 using data from NASA’s now-retired Kepler space telescope, lies in the habitable zone of a star system that’s about 120 light-years away in the constellation Leo. It’s about 8.6 times as massive as Earth, and astronomers regard it as a sub-Neptune — a type of planet that doesn’t exist in our solar system.
Since its initial detection, astrobiologists have been interested in the world’s potential for habitability. They suspected it might be what’s called a Hycean planet — a type of world that’s massive enough to hold onto a hydrogen-rich atmosphere and a globe-spanning sea. The evidence has been piling up: In 2019, researchers reported the chemical signature of water vapor and clouds in K2-18 b’s atmosphere.
The fact that JWST detected an abundance of methane (CH4) and carbon dioxide (CO2), along with a shortage of ammonia (NH3), is consistent with the atmospheric modeling for Hycean planets.
Astronomers have detected thousands of planets, including dozens that are potentially habitable. (NASA Illustration)
When will we find evidence for life beyond Earth? And where will that evidence be found? University of Arizona astronomer Chris Impey, the author of a book called “Worlds Without End,” is betting that the first evidence will come to light within the next decade or so.
“Spectroscopic data is not as appealing to the general public,” Impey admits in the latest episode of the Fiction Science podcast. “People like pictures, and so spectroscopy never gets its fair due in the general talk about astronomy or science, because it’s slightly more esoteric. But it is the tool of choice here.”
A cutaway view shows water rising up from Enceladus’ ice-covered ocean. (NASA / JPL-Caltech Illustration)
Phosphorus, an essential ingredient for life as we know it, has been detected for the first time in water samples that can be traced back to Enceladus, an ice-covered moon of Saturn.
The discovery, reported today in the journal Nature, lends further support to suggestions that life could lurk within Enceladus’ ice-covered oceans — and perhaps in similar environments elsewhere in the solar system.
Phosphorus-containing compounds, known as phosphates, provide the molecular backbone for DNA and RNA molecules. Adenosine triphosphate, or ATP, serves as the source of energy for living cells. This research marks the first time that phosphates have been traced to an extraterrestrial ocean. The Nature paper suggests that phosphate levels in Enceladus’ hidden seas could be hundreds or even thousands of times higher than what exists in Earth’s oceans.
“By determining such high phosphate concentrations readily available in Enceladus’ ocean, we have now satisfied what is generally considered one of the strictest requirements in establishing whether celestial bodies are habitable,” study co-author Fabian Klenner, a postdoctoral researcher at the University of Washington, said in a news release.
An image from NASA’s Galileo orbiter shows Europa’s surface of salt-streaked ice. (Credit: NASA / JPL / Ted Stryk)
A prime target in the search for extraterrestrial life is Europa, a moon of Jupiter that’s covered with a sheet of salty ice. But what kind of salt is there? Researchers say they’ve created a new kind of salt crystal that could fill the bill, and perhaps raise hopes for finding life under the ice.
This salt crystal is both exotic and common: It’s actually table salt — also known as sodium chloride, with the chemical formula NaCl — but bound up with water molecules to form a hydrate that doesn’t exist naturally on Earth.
Earthly sodium chloride hydrates are composed of one salt molecule linked by hydrogen bonds with two water molecules. In contrast, the hydrates created in the lab consist of two NaCl molecules to 17 water molecules, or one NaCl molecule to 13 water molecules. (The structure for a third type of “hyperhydrated hydrate” couldn’t be determined.)
That’s promising news for scientists who study Europa and other ice-covered worlds — including two other Jovian moons, Callisto and Ganymede; and the Saturnian moons Enceladus and Titan. Spectral observations indicate that Europa’s surface ice contains salts, including sodium chloride, but the observed levels of concentration don’t match up well with Earth’s run-of-the-mill NaCl hydrates.
An image from an engineering camera on NASA's Perseverance rover shows its surroundings on Mars. (NASA / JPL-Caltech)
NASA’s Perseverance rover touched down on Mars today and began a mission that’s meant to store up evidence of past life on Mars, after a trip that came to a climax with seven minutes of delicious terror.
“Touchdown confirmed! Perseverance safely on the surface of Mars, ready to begin seeking the signs of past life,” lead controller Swati Mohan declared at 12:55 p.m. PT.
The end of Perseverance’s seven-month, 300 million-mile journey played out like a radio drama. Due to limited bandwidth and an 11-minute delay in receiving signals, there was no live video of the landing. But thanks to internet links, millions of people could listen in as Mohan called out the milestones over a live stream from NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
A socially distanced cadre of controllers at JPL applauded, screamed and exchanged fist bumps after the touchdown. Moments later, the first black-and-white picture from the rover’s hazard avoidance cameras was displayed on a giant screen.
Such findings raise new hopes in the search for life beyond Earth in the solar system, although the conditions that’d be required are close to the edge of plausibility.
The new findings, published this week in Nature Astronomy, take advantage of techniques that look at the smoothness as well as the brightness of radar reflections. The research team includes many of the same scientists who were behind the earlier study, including lead author Elena Pettinelli of the University of Rome.
Pettinelli and her colleagues of ground-penetrating radar readings from MARSIS, an instrument on the European Space Agency’s Mars Express orbiter.
Two years ago, the team identified a spot in Ultimi Scopuli, an area within a Martian region called Planum Australe, where the brightness of the radar echoes hinted at a reservoir of liquid water that might lie a mile beneath layers of ice and dust. But the researchers had only a limited amount of observations to go on.
Since then, they’ve added lots more data, and they also took advantage of new techniques that were field-tested to discover lakes hidden beneath the ice of East Antarctica, Greenland and the Canadian Arctic.
The new analysis confirmed readings related to the 12-mile-wide subsurface lake that was reported in 2018, and what appear to be smaller patches of water, slush or wet soil in the same area.
“These results corroborate the initial discovery … of a stable body of liquid water in Ultimi Scopuli using a different and independent technique, highlighting at the same time a more extensive, complex scenario with ubiquitous water patches surrounding the subglacial lake,” the researchers wrote.
A 55-by-75-mile-wide map of radar readings shows potential reservoirs of subsurface water as bluish patches. (Pettinelli et al. / Univ. of Rome / Nature Astronomy)
However, they say trying to explain how water could exist deep beneath the ice in Mars’ polar region is “at best, a matter of speculation at this point in time.”
They speculate that the water may be heavily laced with perchlorates or other salts that would allow it to exist in liquid form far below the normal freezing point for pure water. Previous Mars missions have turned up evidence of such salts at the surface.
Experiments on Earth have shown that perchlorate brines could remain liquid in a super-cooled state at temperatures as low as 190 degrees below zero Fahrenheit (150 Kelvin).
The researchers say subsurface temperatures at Ultimi Scopuli could come close to that level, and they propose that metastable conditions at depth “are likely to produce a remarkable effect, both in terms of the formation of brines and in terms of their longevity on Mars.”
Perchlorate-laced water is toxic to most life on Earth. In fact, perchlorate is a key ingredient of some types of rocket fuel. Nevertheless, some particularly hardy microbes are able to make a meal out of it — and that might turn out to be the case on Mars as well.
“The possibility of extended hypersaline water bodies on Mars is particularly exciting because of the potential for the existence of microbial life,” the researchers write.
For that reason, they say bodies of water in Mars’ south polar region would “represent areas of potential astrobiological interest and planetary protection concern, and future missions to Mars should target this region.”
The only probe to send data back from a spot anywhere close to Mars’ poles was Phoenix Mars Lander, which detected what may have been splashes of liquid water in 2008 at its landing site in the north polar region. Scientists have talked up ambitious plans for polar expeditions on Mars for decades, but so far there’s been little follow-through.
Should there be? Or should more attention be devoted to other potential targets in the search for life elsewhere in the solar system, ranging from Venus to Europa and Enceladus?
It’s going to be hard to miss Mars in the weeks ahead: The Red Planet is getting brighter every night as it nears the closest point to Earth in its current orbit on Oct. 6, followed by opposition on Oct. 13.
Opposition is the time when Mars lines up directly opposite from the sun, as seen from Earth. This season is considered prime time for viewing Mars, which has started outshining Jupiter in the night sky. (Only Venus shines brighter in this month’s planetary parade.)
Mars gleams as a butterscotch-colored star in eastern skies after sunset — and at opposition, it should be right above you around midnight.
Mars is in opposition every 26 months, but some close encounters are closer than others. This time around, Mars will be only 38.6 million miles from Earth. The next time Mars comes this close will be in 2035.
In addition to Pettinelli, the authors of the Nature Astronomy study, “Multiple Subglacial Water Bodies Below the South Pole of Mars Unveiled by New MARSIS Data,” include Sebastian Emanuel Lauro, Graziella Capranelli, Luca Guallini, Angelo Pio Rossi, Elisabetta Mattei, Barbara Cosciotti, Andrea Cicchetti, Francesco Soldovieri, Marco Cartacci, Federico Di Paolo, Raffaella Noschese and Roberto Orosei.
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.
“If they have the right instrument and they can take a look at Venus, that’d be awesome,” Seager said. “It would be great to get whatever observations we can.”
Update for 9:25 a.m. PT Sept. 17: I’ve updated this report with Seager’s comments on how much support will be provided by the Breakthrough Initiatives.
This false-color image of Venus is based on ultraviolet data from Japan's Akatsuki probe. (JAXA / ISAS / Akatsuki Project Team /
CC BY 4.0)
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.”
On Earth, microbes are routinely lofted into upper levels of the atmosphere and eventually drift back down. But on Venus, such organisms would be killed off if they sank too low. Such an exclusively aerial biosphere might have evolved from an earlier age when Venus was far more hospitable to life, Sousa-Silva said.
“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.
Yet another Discovery Program finalist, the proposed VERITAS mission, would concentrate on creating three-dimensional maps of Venus’ surface features and geology. NASA is also considering a CubeSat mission to study Venus’ atmosphere.
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:
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.
