Venus

FEATURE: Venus

After a tantalizing discovery at Venus, what could an astrobiology mission look like?

Suddenly, a mission to investigate whether Venus might be hospitable to life after all doesn’t seem quite so outlandish.
Astronomers announced Monday (Sept. 14) that they have identified phosphine, a chemical some scientists have proposed may be a sign of life, in the clouds of Venus. The new research relied on data from two ground-based telescopes, and scientists already have plans to tug a little more at the Venusian mystery from Earth’s surface.
But, if we really want to know what’s going on with this strange chemical in the thick, acidic clouds of our planetary neighbor, we’re going to need to get a lot closer, even right into Venus’ clouds — where no spacecraft has ventured in 35 years.
“This is something more that we can’t explain about Venus,” Sanjay Limaye, an atmospheric scientist at the University of Wisconsin, Madison, who wasn’t involved in the new study, told Space.com. “Venus has got more questions [about it] than Mars, which is why we are suggesting that Venus should be considered an astrobiology target.”
It’s not that scientists haven’t wanted to explore Venus more thoroughly, of course. But the planet is seriously rough on the vital organs of a spacecraft. Take a computer, some electronics and a bunch of ultra-sensitive instruments and send them through acidic clouds to a surface that’s essentially a broiling pressure cooker, and, well, it isn’t pretty. In fact, no spacecraft has ever survived a full two hours on the surface of Venus.
“Venus is ready for the armada to get there, but it’s less forgiving than Mars,” James Garvin, a planetary scientist at NASA’s Goddard Space Flight Center in Maryland, who wasn’t involved in the new research but is the principal investigator on a Venus atmospheric probe mission that NASA is evaluating, told Space.com.
That said, engineers have been busy in the decades since the last spacecraft ventured into Venus’ atmosphere when the Soviet Vega probes did so in the mid-1980s. With the added impetus created by the tantalizing new research, scientists hope that agencies may now turn their sights to more — and more daring — Venus missions.
“I think this is catalytic,” Garvin said of the potential impact of the new research on the motivation to explore Venus. “After a mad foray, a flourish of attempts to understand Venus in the ’70s and early ’80s, there was a hiatus and it’s actually been 35 years since any mission by any country on this planet has visited the atmosphere of Venus.”
Back to Venus?
Right now, Venus has just one spacecraft companion, Japan’s Akatsuki orbiter. Akatsuki launched in 2010 and, while it flubbed its first attempt to orbit Venus later that year, it succeeded on a second attempt in 2015. The spacecraft has spent its tenure studying the weather on Venus and looking for flashes of lightning — all from a safe orbit, of course.
NASA’s, however, hasn’t had a dedicated mission to Venus since the Magellan probe orbited from 1990 to 1994. But the new research may prompt NASA to end that drought. “It’s time to prioritize Venus,” NASA Administrator Jim Bridenstine wrote in a tweet on Monday about the phosphine detection, which he called “the most significant development yet in building the case for life off Earth.”
NASA is evaluating two Venus-targeted proposals in its current round of so-called Discovery projects, the same class of mission that includes the Lunar Reconnaissance Orbiter, the geophysics InSight lander on Mars and the upcoming asteroid missions Lucy and Psyche.
Other space agencies are also considering a visit. India’s space agency is considering a mission called Shukrayaan-1, an orbiter that would launch in 2023 and study Venus’ surface. Russia is considering a hardier version of its Soviet-era landers, a longer-lived surface mission. The European Space Agency (ESA) isevaluating a proposal for a mission called EnVision, a geology orbiter that would launch in 2032 and could tell scientists about alternative explanations for the phosphine detection, such as by determining whether the planet hosts active volcanoes that could be producing the gas.
Scientists say that the engineering is ready for such missions, and we long ago hit the point where we had machinery worth sending. “It’s so frustrating that we have the technology and have had much of this technology for so long and we’re just ready to bring this to bear on Venus now,” Darby Dyar, a planetary scientist at the Planetary Science Institute and the deputy principal investigator on the second mission proposal NASA is currently considering, told Space.com. “Venus offers a smorgasbord of really cool missions that you can do.”
There are plenty of other Venus mission concepts out there that aren’t formally under agency review, ranging all the way from modest endeavors to NASA’s most ambitious (and most expensive) category of projects, on the scale of the agency’s sophisticated Mars rovers Curiosity and Perseverance.
But we’ll need several spacecraft to really understand the story of Venus. “There’s not a single mission,” Limaye said. “It’s a collection of missions because there are so many different investigations that not a single mission can address all the questions and it’ll be a fight to decide which missions should be flown first.”
(Venus scientists, even those proposing specific missions, regularly emphasize that because Venus is so understudied, any mission to go there at all would be an improvement over the status quo.)
In the context of the phosphine detection announced this week, there are two ways future missions could build on the new research. Either spacecraft could confirm the detection itself, or they could develop our larger understanding of Venus, helping scientists interpret the detection.
Investigating phosphine up close
The new claim of detecting phosphine at Venus is based only on observations taken by ground-based telescopes, but those observations pose two key challenges.
The first is that there’s still a chance the detections weren’t actually of phosphine: The scientists studied only a small window of the spectral signature — a sort of chemical barcode, in which the researchers saw only what corresponded to one line of the code. In order to more confidently identify the chemical, scientists will need to be able to see one or more other lines of that signature.
A second challenge is that the telescopes the scientists used can’t identify precisely where in Venus’ atmosphere the phosphine might be. All scientists know so far is that it must be more than 30 miles (50 kilometers) above the surface of Venus. Without a more precise understanding of the signal’s altitude, it’s difficult to know what environment the chemical may be in.
Breaking the decades-long drought of atmospheric probes at Venus should help scientists to manage both of those challenges.
“We’d like to see really any kind of mission go back to Venus,” Sara Seager, an astronomer at the Massachusetts Institute of Technology and co-author on the new research, said during a news conference held on Monday (Sept. 14). “Something that’s capable of measuring gases in the atmosphere, something that has a so-called mass spectrometer that can identify larger complex molecules that could only be associated with life,” she said, describing her mission wishlist, adding that a balloon might be the best design for such a spacecraft.
While it isn’t a balloon, one of the two missions NASA is currently considering would be equipped to tackle the phosphine mystery head-on, Garvin said of the mission proposal he leads, called DAVINCI+ (short for Deep Atmosphere Venus Investigation of Noble Gases, Chemistry, and Imaging Plus).
DAVINCI+ is a two-part mission that includes a probe that would travel through Venus’ entire atmosphere to the planet’s surface in about an hour, sampling as it goes, and an orbiter that would study the atmosphere of Venus’ daylight side and the terrain of its night side for a full Venusian year, or 225 Earth days.
The probe’s descent, in particular, would tell scientists whether the phosphine detection was real and confirm how prevalent the gas is in the Venusian atmosphere. It would also give scientists the thorough understanding of chemistry on Venus that is severely lacking, stymying researchers’ attempts to interpret data.
And, while the mission may sound a bit unprecedented, it isn’t really, Garvin said. The chemical laboratory at the heart of DAVINCI+ would be essentially the same as those in NASA’s Mars Curiosity and Perseverance rovers and the Dragonfly drone that the agency will send to fly on Saturn’s strange moon Titan, a mission due to launch in 2026.
“The same way we brought that story to Mars with the Curiosity, and soon Perseverance, rovers; we want to invert that and bring it to the atmosphere, essentially developing a flying sampling rover, that instead of driving, it’s flying and falling,” Garvin said. “We have to bring the best-instrumented chemistry lab to the samples we want to study in the Venus atmosphere with 21st-century gear.”
A step farther
The other Venus mission NASA is currently evaluating could build on the phosphine detection in a different way. VERITAS (short for Venus Emissivity, Radio Science, InSAR, Topography and Spectroscopy) wouldn’t probe the atmosphere directly and wouldn’t be able to confirm the phosphine detection up close.
Instead, it’s an orbiter that would use radar and spectroscopy to study the surface of Venus. VERITAS is designed to produce a high-resolution topographical map of Venus and identify what types of rocks are found on its surface and where.
“To get the first look at global composition at least is going to tell us so much, even if the method is not everything you might wish for,” Sue Smrekar, a planetary geophysicist at NASA’s Jet Propulsion Laboratory in California and the principal investigator on the VERITAS proposal, told Space.com. “It’s going to be, I think, really spectacular in terms of enhancing our understanding of surface chemistry.”
The data collected by VERITAS could help scientists address ongoing mysteries like how long Venus had an ocean and how quickly it disappeared, or whether there are still active volcanos spewing chemicals into the planet’s atmosphere from its deep innards. Understanding these issues could determine whether the detected phosphine can be explained without invoking life.
VERITAS and DAVINCI+ are two of four concepts from which Thomas Zurbuchen, NASA’s associate administrator for the Science Mission Directorate will select one or more missions next spring. Like his boss Bridenstine, Zurbuchen expressed excitement about the new phosphine finding, calling the paper “intriguing,” although he was less gung-ho in his remarks.
“We trust in the scientific peer review process & look forward to the robust discussion that will follow its publication,” Zurbuchen wrote on Twitter, referencing both the consideration of VERITAS and DAVINCI+, and NASA’s involvement in ESA’s potential EnVision mission.
One thing is for sure: if these or any other missions visit our neighboring world, Venus scientists will be thrilled.
“The ’20s could be a rebirth of using Venus as a clue to the solar system and accessible universe, the same way we’ve used Mars and the moon and now [Jupiter’s moon] Europa so compellingly.” Garvin said, adding that he hopes space agencies use this decade to gather the data that has been so sorely lacking about our neighboring world.
“If we can do that in the ’20s, the ’30s will erupt into this beautiful masterpiece of new kinds of missions: Titan, hopefully also to Venus, Mars, women living on the moon. I mean, it’s going to be a different space age.” Garvin said. “To be honest, I wouldn’t be surprised if we wake up in the ’30s and say, ‘Oh, my god, how could we have missed this?”

In Space.com

www.space.com/venus-astrobiology-mission-designs-phosphine.html

Possible sign of life on Venus stirs up heated debate

“Something weird is happening” in the clouds of the planet next door—but some experts are raising doubts about the quality of the data.
SOMETHING DEADLY MIGHT be wafting through the clouds shrouding Venus—a smelly, flammable gas called phosphine that annihilates life-forms reliant on oxygen for survival. Ironically, though, the scientists who today announced sightings of this noxious gas in the Venusian atmosphere say it could be tantalizing—if controversial—evidence of life on the planet next door.
As far as we know, on rocky planets such as Venus and Earth, phosphine can only be made by life—whether human or microbe. Used as a chemical weapon during World War I, phosphine is still manufactured as an agricultural fumigant, is used in the semiconductor industry, and is a nasty byproduct of meth labs. But phosphine is also made naturally by some species of anaerobic bacteria—organisms that live in the oxygen-starved environments of landfills, marshlands, and even animal guts.
Earlier this year, researchers surmised that finding the chemical on other terrestrial planets could indicate the presence of alien metabolisms, and they suggested aiming the sharpest telescopes of the future at faraway exoplanets to probe their atmospheres for signs of the gas.
Now, we may have found signs of phosphine on the planet next door, astronomers report in the journal Nature Astronomy.
“I immediately freaked out, of course. I presumed it was a mistake, but I very much wanted it to not be a mistake,” says study co-author Clara Sousa-Silva, a postdoctoral researcher at the Massachusetts Institute of Technology (MIT) who initially identified phosphine as a potential biosignature.
Put simply, phosphine shouldn’t be in the Venusian atmosphere. It’s extremely hard to make, and the chemistry in the clouds should destroy the molecule before it can accumulate to the observed amounts. But it’s too early to conclude that life exists beyond Earth’s shores. Scientists caution that the detection itself needs to be verified, as the phosphine fingerprint described in the study could be a false signal introduced by the telescopes or by data processing.
“It’s tremendously exciting, and we have a sort of obligatory response of first questioning whether the result is real,” says David Grinspoon of the Planetary Science Institute. “When somebody comes up with an extraordinary observation that hasn’t been made before, you wonder if they could have done something wrong.”
But if phosphine really is floating through the Venusian cloud deck, its presence suggests one of two intriguing possibilities: that alien life-forms are deftly linking together phosphorus and hydrogen atoms, or that some completely unanticipated chemistry is crafting phosphine in the absence of life.
Life on a “blasted hellhole”
Venus, the second world from the sun, has long been considered Earth’s twin. It’s about the same size as our home planet, with similar gravity and composition. For centuries, hopeful humans thought its surface might be covered in oceans, lush vegetation, and verdant ecosystems, providing a second oasis for life in the solar system.
Then reality intruded.
Early science observations of the planet next door revealed that it is a menace of a world that could kill Earthlings in multiple ways. Its surface can reach a sweltering 900 degrees Fahrenheit. Tucked beneath as many as 65 miles of cloud and haze, those roasted rocks are smothered by a bone-crushing amount of pressure, more than 90 times what’s felt on Earth’s surface. Plus, the planet’s atmosphere is primarily suffocating carbon dioxide populated by sulfuric acid clouds.
Even so, scientists have considered the possibility that life might exist in the Venusian cloud deck for nearly 60 years, perhaps thriving where conditions are a bit friendlier.
“While the surface conditions of Venus make the hypothesis of life there implausible, the clouds of Venus are a different story altogether,” Carl Sagan and Harold Morowitz wrote in the journal Nature back in 1967.
Despite the acid, the clouds carry the basic ingredients for life as we know it: sunlight, water, and organic molecules. And near the middle of the cloud layer, temperatures and pressures are rather Earthlike. “It’s shirt-sleeve weather, with all these tasty things to eat,” says Martha Gilmore, a Wesleyan University planetary scientist and leader of a proposed mission to Venus, referring to molecules in the planet’s air that microbes could metabolize.
Early observations of the planet revealed that parts of its atmosphere absorb more ultraviolet light than expected, an anomaly that scientists hypothesized could be the work of aerial microbes. While the phenomenon is more likely due to the presence of sulfur-containing compounds, a handful of scientists have since elaborated on the possibility of airborne Venusians, laying out scenarios in which microbes might metabolize sulfur compounds, stay afloat among the ever-present clouds, and even develop life cycles enabled by periods of dormancy at varying altitudes.
“When I first started talking about it, there was a lot of resistance, mostly because it’s such a harshly acidic environment,” says Grinspoon, who has pushed the idea of cloud-borne life on Venus since the mid-1990s.
But everything we’ve learned about life on Earth suggests that it will move into every available nook and cranny. Here, we find microbes thriving in hostile, corrosive environments such as hot springs and volcanic fields. We also know that microbes regularly hitch a ride on cloud particles, and scientists have found organisms flying more than six miles above the Caribbean. Clouds are ephemeral on Earth, so it’s unlikely that they support permanent ecosystems, but on Venus, cloudy days are in the forecast for millions or even billions of years.
“On Venus, that puddle never dries up,” Grinspoon says. “The clouds are continuous and thick and globe-spanning.”
Although Venus is a roasting world today, observations suggest that it once had a liquid water ocean. For most of its history, Venus could have been as habitable as Earth—until sometime in the last billion years, when ballooning greenhouse gases transformed the planet from an oasis into a death trap. Perhaps, as the scorched surface became less hospitable, life-forms migrated into the clouds to avoid certain extinction.
Any life there now is “much more likely to be a relic of a more dominating early biosphere,” says Penelope Boston, a NASA astrobiologist who specializes in studying microbes in weird places on Earth. She’s skeptical, though. “I think it’s a blasted hellhole now, so how much of that ancient signal could have held up?”
The deadly gas of life
In June 2017, Cardiff University’s Jane Greaves and colleagues took a look at Venus using the James Clerk Maxwell Telescope, which scans the sky in radio wavelengths from its perch atop Mauna Kea in Hawaii. They were looking for rare gases or molecules that might be biological in origin. Among the signatures they spotted was that of phosphine gas, a pyramidal molecule comprising three hydrogen atoms joined to a single phosphorus atom.
Not long after, Greaves got in touch with Sousa-Silva, who spent her years in graduate school working out whether phosphine could be a viable extraterrestrial biosignature. She had concluded that phosphine could be one of life’s beacons, even though paradoxically, it’s lethal to everything on Earth that requires oxygen to survive.
“I was really fascinated by the macabre nature of phosphine on Earth,” she says. “It’s a killing machine … and almost a romantic biosignature because it was a sign of death.”
In 2019, Greaves, Sousa-Silva, and their colleagues followed up on the initial phosphine observation using ALMA, an array of telescopes on a high Chilean plateau. More sensitive than the Hawaii-based telescope, ALMA also observes the sky at radio frequencies, and it can detect the energy emitted and absorbed by any phosphine molecules spinning in the Venusian atmosphere.
Again, the team detected phosphine. This time, scientists could narrow down the molecule’s signal to equatorial latitudes and an altitude between 32 and 37 miles, where temperatures and pressures aren’t too harsh for life as we know it. Based on the signal’s strength, the team calculated that phosphine’s abundance is roughly 20 parts per billion, or at least a thousand times more than we find on Earth.
In the outer solar system, phosphine is made deep in the interiors of Jupiter and Saturn. Near the giant planets’ cores, the temperatures and pressures are extreme enough to craft the molecule, which then rises through the atmosphere. But on rocky planets, where conditions are significantly less extreme, there’s no known way to make phosphine in the absence of life—it’s just too energetically demanding. In other words, if the observation of phosphine on Venus is right, something must be continually replenishing the molecule in the planet’s atmosphere.
“Life is the only thing that will put energy into making molecules,” Sousa-Silva says. “Otherwise, in the universe, chemistry only happens when it’s energetically favorable.”
Astrobiologist Dirk Schulze-Makuch of Technical University Berlin, who has considered cloud-based Venusian life, agrees a biological explanation for the phosphine is possible, but he thinks other unknown geologic or light-induced chemical reactions might yet account for the signal. “Venus is basically still an alien planet,” he says. “There are a lot of things we don’t understand.”
The study team set out to determine whether phosphine could be made on Venus in the absence of biology. Among the scenarios the scientists investigated were volcanic outgassing, intense lightning strikes, tectonic plates rubbing together, bismuth rain, and cosmic dust. Based on the team’s calculations, none of those events could produce the molecule in such abundance.
“Whether it’s life or not, it has to be a really exotic mechanism,” Sousa-Silva says. “Something weird is happening.”
Getting back to Venus
Still, ALMA observatory scientist John Carpenter is skeptical that the phosphine observations themselves are real. The signal is faint, and the team needed to perform an extensive amount of processing to pull it from the data returned by the telescopes. That processing, he says, may have returned an artificial signal at the same frequency as phosphine. He also notes that the standard for remote molecular identification involves detecting multiple fingerprints for the same molecule, which show up at different frequencies on the electromagnetic spectrum. That’s something that the team has not yet done with phosphine.
“They took the right steps to verify the signal, but I’m still not convinced that this is real,” Carpenter says. “If it’s real, it’s a very cool result, but it needs follow-up to make it really convincing.”
Sousa-Silva agrees that the team needs to confirm the phosphine detection by finding additional fingerprints at other wavelengths. She and her colleagues had planned such observations using the Stratospheric Observatory for Infrared Astronomy, a plane-mounted telescope, and with NASA’s Infrared Telescope Facility in Hawaii. But COVID-19 got in the way, and the team’s attempts have been put on hold.
“It’s disappointing that we don’t have this proof,” Sousa-Silva says.
Even so, Sanjay Limaye, a planetary scientist at the University of Wisconsin-Madison, says the discovery is exciting enough to continue searching, and preferably from a much closer vantage point. “It is intriguing that it may point to something strange going on in the atmosphere of Venus, but is it exotic chemistry, or is it life?” he says. “We need to go explore and find out.”
The tentative detection of phosphine is likely to fuel calls for a return to Venus—a trip that some say is long overdue, given that the last time NASA sent a probe to the planet was in 1989. Schulze-Makuch says it’s completely within the realm of possibility to do an atmospheric sample-return mission, sending a spacecraft to swoop through the clouds and gather gas and particles to bring back to Earth.
Several proposed missions are moving through review, including an elaborate, multi-spacecraft concept led by Gilmore of Wesleyan University, which will be evaluated by the planetary science community as it sets its priorities for the next decade of solar system exploration. Gilmore’s concept includes several orbiters and a balloon that would closely study the Venusian atmosphere and look for signs of life.
On the more immediate horizon, a smaller mission to study the deep atmosphere of Venus, named DAVINCI+, is one of the four finalists in NASA’s Discovery program competition. The next mission selection is scheduled to take place in 2021.
“Venus is such a complex, amazing system, and we don’t understand it. And it’s another Earth. It probably had an ocean for billions of years, and it’s right there. It’s just a matter of going,” Gilmore says. “We have the technology right now to go into the atmosphere of Venus. It can be done.”

In National Geographic

www.nationalgeographic.com/science/2020/09/possible-sign-of-life-found-on-venus-phosphine-gas/

Spacecraft to fly past Venus weeks after signs of life detected in planet’s atmosphere

A spacecraft with the intended destination of Mercury is expected to make a close flyby of Venus in mid-October, providing scientists with the chance to gather additional information to back up recent revelations that the distant planet may in fact harbor life.
The spacecraft in question – BepiColombo – is part of a joint international project between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency. The craft’s mission is intended to study Mercury’s composition, geophysics, atmosphere, magnetosphere and overall history.
Although BepiColombo may provide scientists with a vast amount of information on Mercury in a few years’ time, the space mission will be able to give officials further insight into Venus sooner, since the craft will have to conduct two Venus flybys as it attempts to use the planet’s gravitational pull to curb its speed before heading to Mercury.
According to the ESA, the first of the two flybys is expected to take place on October 15. Although the date of the second flyby is yet to be officially confirmed, a tentative date of August 10, 2021, has been noted.
While the agency has already indicated that the instruments aboard BepiColombo have been designed to specifically function for Mercury’s environment, the ESA has stated that the mission still has the capabilities to possibly investigate Venus’ atmosphere and ionosphere.
“It’s kind of perfect timing,” Jorn Helbert, whose team from the German Aerospace Center helps to manage instruments on the ESA’s orbiter, told Forbes. “We are now seeing if our sensitivity is good enough to do observations.”
Helbert told the outlet that he believes the Mercury Radiometer and Thermal Imaging Spectrometer (MERTIS) device aboard ESA’s orbiter would be best at studying Venus’ atmosphere, but that ultimately there is still a possibility that it may not be successful, since the device was made for Mercury and will be at a distance of over 6,200 miles from Venus.
However, the second flyby, which will place the BepiColombo at a distance of about 340 miles from the planet, may prove much more fruitful, Helbert said. And on the chance that it’s a success, MERTIS will likely be able to confirm whether phosphine gas, potentially a sign of microbial life, exists on Venus.
The agency would have to get “very, very lucky” to detect phosphine on Venus during the first flyby, Helbert said.
An international team of researchers stunned many in the science communities earlier this week after they announced that they’d discovered potential signs of life on Venus. Their study, which was published September 14 in the journal Nature Astronomy, detailed that traces of phosphine had been spotted in Venus’ hazy, yellow clouds.

In Space Daily

www.spacedaily.com/reports/Spacecraft_to_fly_past_Venus_weeks_after_signs_of_life_detected_in_planets_atmosphere_999.html

Venus’ ancient layered, folded rocks point to volcanic origin

An international team of researchers has found that some of the oldest terrain on Venus, known as tesserae, have layering that seems consistent with volcanic activity. The finding could provide insights into the enigmatic planet’s geological history.

Tesserae are tectonically deformed regions on the surface of Venus that are often more elevated than the surrounding landscape. They comprise about 7% of the planet’s surface, and are always the oldest feature in their immediate surroundings, dating to about 750 million years old. In a new study appearing in Geology, the researchers show that a significant portion of the tesserae have striations consistent with layering.

“There are generally two explanations for tesserae – either they are made of volcanic rocks, or they are counterparts of Earth’s continental crust,” says Paul Byrne, associate professor of planetary science at North Carolina State University and lead author of the study. “But the layering we find on some of the tessera isn’t consistent with the continental crust explanation.”

The team analyzed images of Venus’ surface from NASA’s 1989 Magellan mission, which used radar to image 98% of the planet through its dense atmosphere. While researchers have studied the tesserae for decades, prior to this work the layering of the tesserae hasn’t been recognized as widespread. And according to Byrne, that layering would not be possible if the tesserae were portions of continental crust.

“Continental crust is composed mainly of granite, an igneous rock formed when tectonic plates move and water is subducted from the surface,” Byrne says. “But granite doesn’t form layers. If there’s continental crust on Venus, then it’s below the layered rocks we see.

“Aside from volcanic activity, the other way to make layered rock is through sedimentary deposits, like sandstone or limestone. There isn’t a single place today on Venus where these kinds of rocks could form. The surface of Venus is as hot as a self-cleaning oven and the pressure is equivalent to being 900 meters (about 985 yards) underwater. So the evidence right now points to some portions of the tesserae being made up of layered volcanic rock, similar to that found on Earth.”

Byrne hopes that the work will help to shed light on more of Venus’ complicated geological history.

“While the data we have now point to volcanic origins for the tesserae, if we were one day able to sample them and find that they are sedimentary rocks, then they would have had to have formed when the climate was very different – perhaps even Earth-like,” Byrne says.

“Venus today is hellish, but we don’t know if it was always like this. Was it once like Earth but suffered catastrophic volcanic eruptions that ruined the planet? Right now we cannot say for certain, but the fact of the layering in the tesserae narrows down the potential origins of this rock.”

In Space Daily

www.spacedaily.com/reports/Venus_ancient_layered_folded_rocks_point_to_volcanic_origin_999.html

Full Research Report “Venus tesserae feature layered, folded, and eroded rocks” at https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G47940.1/590731/Venus-tesserae-feature-layered-folded-and-eroded?redirectedFrom=fulltext

Tesserae on Venus are locally the stratigraphically oldest units preserved on the planet. These regions are characterized by pervasive tectonic deformation including normal faults, grabens, thrust faults, and folds. In multiple tesserae, sets of (often highly) curved, parallel linear features are also present. These features strongly resemble terracing in layered volcanic or sedimentary sequences on Earth having arcuate or sinuous outcrop patterns that follow undulating topography. Should this analogy hold for Venus, then these outcrop patterns imply some erosion of the tessera units in which these strata occur; radar-dark materials filling proximal lows might be deposits of that eroded material. This outcrop pattern is seen in geographically dispersed tessera units, so the preservation of layering could be common for this terrain type. If so, then tesserae record the culmination of volcanic and/or sedimentary deposition, folding, and erosion—complex geological histories that should be considered in future studies of this enigmatic terrain.

Did Scientists Just Find Signs of Life on Venus?

A team of scientists has just published a paper announcing their discovery of a peculiar chemical in the cloudtops of Venus. As far as scientists can tell, this chemical, called phosphine, could only be produced by living processes on a planet like Venus. So the whole internet is jumping on this story.
But did they find signs of life? Or is there another explanation?
Decades ago, scientists and script writers wondered about life on Venus. No spacecraft had visited, and we couldn’t see through the thick, hazy atmosphere, so imaginations were unfettered. Almost anything could be going on down there, out of sight. Once spacecraft started visiting in the early 1960s, however, it became clear that life on Venus was unlikely. Venus was revealed as a blistering hot hellhole, with a toxic atmosphere and crushing pressure.
But the thinking behind life on Venus didn’t disappear completely. In recent times, scientists have wondered if simple life might survive in Venus’ unusually cloudy atmosphere. Extremophiles, the thinking goes, might be able to survive in the acidic upper parts of the planet’s atmosphere, where temperatures were cooler than the 462 degree Celsius (864 F) surface temperatures. In those upper layers, the pressure and temperature is similar to Earth’s.
That’s where the discovery of phosphine (PH3) in the clouds comes in.
“The reason phosphine is special is, without life it is very difficult to make phosphine on rocky planets”, Clara Sousa-Silva, Co-Author, MIT’s Department of Earth, Atmospheric and Planetary Sciences
The new study announcing this discovery is titled “Phosphine gas in the cloud decks of Venus.” It’s published in the journal Nature Astronomy, and the lead author is Jane Greaves of Cardiff University. Other authors come from MIT, Cambridge, and a handful of other research institutions around the world.
First of all, the discovery of phosphine is not direct evidence of life. Phosphine is a possible biomarker. That means we know that it can be produced by microorganisms. Here on Earth, it’s produced by organisms on decaying organic matter, and phosphine is a regular constituent of the atmosphere. As far as scientists know, phosphine is either produced by life, or by chemical processes that require an enormous amount of energy.
Phosphine has also been found in Jupiter’s atmosphere. On a gas giant like Jupiter, there’s enough energy for phosphine to form abiotically. Deep in the atmosphere, extreme temperature and pressure can create phosphine, and currents can dredge it up high into the atmosphere. But on a lifeless, rocky world like Venus, phosphine is not supposed to be there. It should be oxidized, and there just isn’t enough energy there to produce it.
“If this is not life, then our understanding of rocky planets is severely lacking”, Co-Author Janusz Petkowski, Research Scientist, MIT’s Dept. of Earth, Atmospheric and Planetary Sciences
So its presence in Venus’ atmosphere has caught everyone’s attention.
The team is very confident that they’ve found phosphine. In their paper they write “We are unable to find another chemical species besides PH3 that can explain the observed features. We conclude that the candidate detection of PH3 is robust…”.
They made an exhaustive analysis of their findings, trying to come up with some way that Venus’ phosphine could be explained without a living source. In their paper they write that “The presence of PH3 is unexplained after exhaustive study of steady-state chemistry and photochemical pathways, with no currently known abiotic production routes in Venus’s atmosphere, clouds, surface and subsurface, or from lightning, volcanic or meteoritic delivery.”
The team is hoping that other scientists can find an explanation.
“It’s very hard to prove a negative,” says Clara Sousa-Silva, research scientist in 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 that. Please do, because we are at the end of our possibilities to show abiotic processes that can make phosphine.”
The phospine has to either come from life, or there’s a chemical process at work that scientists don’t know about yet.
“This means either this is life, or it’s some sort of physical or chemical process that we do not expect to happen on rocky planets,” adds co-author and EAPS Research Scientist Janusz Petkowski.
The location of the phosphine is part of what’s piqued everyone’s interest.
Venus’ atmosphere is hot, dense, toxic, and extremely acidic. It can be a billion times more acidic than Earth, stretching the definition of what we would call an extreme environment for life. “Venus is a very challenging environment for life of any kind,” Seager says.
But there’s one region, high in Venus’ atmosphere, where things are different.
Between about 48 and 60 km (30 and 37 miles) above the surface, the temperature isn’t so lethal. At that altitude, the temperature ranges from -1 C to 93 C (30 to 200 degrees F). It’s very controversial, but some scientists have wondered if life could survive there. And that’s where this team of researchers found the phosphine.
“This phosphine signal is perfectly positioned where others have conjectured the area could be habitable,” Petkowski says.
Greaves and her team made the initial phosphine detection with the James Clerk Maxwell Telescope in Hawaii. They were looking for unexpected molecules in Venus’ atmosphere that might be signals for life. Then they contacted Sousa-Silva, who is an expert in phosphine.
Sousa-Silva is interested in phosphine because it’s a biosignature. But she expected to be looking on distant exoplanets for the molecule, as part of the overall scientific effort to identify life elsewhere in the galaxy.
“I was thinking really far, many parsecs away, and really not thinking literally the nearest planet to us,” Sousa-Silva said in a press release.
The team wanted more confirmation for their finding, so they turned to the European Southern Observatory’s ALMA (Atacama Large Millimeter/sub-millimeter Array). It has greater sensitivity than the James Clerk Maxwell Telescope (JCMT), which made the initial finding. ALMA observations confirmed what the team had found: a pattern of light that matched what phosphine gas would emit within Venus’ clouds.
With their ALMA and JCMT data, they turned to a model of Venus’ atmosphere to help make sense of it. That model was developed by Hideo Sagawa of Kyoto Sangyo University. Sagawa is also a co-author of the new study.
The results of that showed that phosphine was a very minor part of Venus’ atmosphere, at a concentration of only 20 ppb (parts per billion.) Though that’s an extremely tiny fraction, in Earth’s atmosphere, where the only source is biological, the concentration can be even lower.
Then the team got busy trying to fit their findings with everything that scientists know about Venus. They explored all the pathways that could explain the presence of phosphine without life. They considered a whole host of possibilities involving sunlight, surface minerals, volcanic activity, a meteor strike, and lightning.
“We really went through all possible pathways that could produce phosphine on a rocky planet,” Petkowski says. “If this is not life, then our understanding of rocky planets is severely lacking.”
If life is behind this phosphine, then that life is in a tough spot. It’s trapped in Venus’ temperate cloud deck, way above the planet’s hellish surface. How did it get there?
Scientists think that Venus may have been habitable billions of years ago. It may even have had oceans. It may even have been the first habitable planet in our Solar System. It’s possible that any life living in the clouds is a descendant of ancient surface life, just like remnants of Earth’s early life are surviving in oxygen poor muds, banished by the changing conditions.
“A long time ago, Venus is thought to have oceans, and was probably habitable like Earth,” Sousa-Silva says. “As Venus became 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. This could show that even a planet at the edge of the habitable zone could have an atmosphere with a local aerial habitable envelope.”
It would be a strange form of life that could exist in Venus’ clouds. It would have to perpetually reproduce. And it would have to use a liquid other than water for its cellular functions. “You can, in principle, have a life cycle that keeps life in the clouds perpetually,” says Petkowski, who envisions any aerial Venusian life to be fundamentally different from life on Earth. “The liquid medium on Venus is not water, as it is on Earth.”
The team intends to follow up these results with more research. They want to use other telescopes to try and map out the phosphine, and to see if it comes and goes in daily or seasonal cycles, which might suggest that life is behind it.
This isn’t the first time that scientists have found potential signs of life in the Venusian atmosphere. But most chemical signs of life can be produced by non-living processes, too. Phosphine is different.
“Technically, biomolecules have been found in Venus’ atmosphere before, but these molecules are also associated with a thousand things other than life,” Sousa-Silva says. “The reason phosphine is special is, without life it is very difficult to make phosphine on rocky planets. Earth has been the only terrestrial planet where we have found phosphine, because there is life here. Until now.”
So that’s where it stands for now. There are plenty of headlines out there saying, or at least implying, that scientists have found signs of life on Venus. But it’s a little more nuanced than that.
While phosphine can be a sign of life, it can also not be one. The truth is we just don’t know yet. As co-author Sousa-Silva says, “It’s very hard to prove a negative.” And as we get better and better at studying other planets and moons, we’re finding a bewildering variety of physical and chemical processes and outcomes.
This could be, and probably is, one of those.
It’s intriguing to think what it’ll look like if we ever do find life elsewhere. The Hollywood/Sci-Fi version of that often involves the sudden appearance of a technologically advanced alien race, their enormous ships hovering menacingly over Earth’s cities. Or a brave team of explorers/scientists investigating some distant world suffers death by xenomorphic parasitic reproduction.
But in reality, it might look more like this. A tiny chemical signal, faint at first, then verified by stages. Just a single type of unlikely molecule, lurking where it shoudn’t be. Unexpected and persistent.