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What Phosphine Means on Venus

A biosignature is always going to create a rolling discussion that gradually homes in on a consensus. Which is to say that the recent discovery of phosphine in the upper atmosphere of Venus has inspired a major effort to figure out how phosphine could emerge abiotically. After all, the scientists behind the just published paper on the phosphine discovery seem to be saying something to the community like “We can’t come up with a solution other than life to explain this. Maybe you can.”

The ‘maybes’ are out there and they include life, but what a tough spot for life to develop, for obvious reasons, not the least of which is the hyper-acidic nature of its clouds. So let’s dig into the story a bit more. The idea of life in the cloud layers of an atmosphere has a long pedigree, even on Venus, where discussions go back at least to the 1960s. Harold Morowitz and Carl Sagan examined the matter in a paper in Science in 1967, a speculation that led them to conclude “it is by no means difficult to imagine an indigenous biology in the clouds of Venus.”

And while the temperature at Venus’ surface can reach 480° Celsius, the temperatures between 48 and 60 kilometers above the surface are relatively benign, in the range of 1° to 90° C. A team led by Jane Greaves (Cardiff University) detected the spectral signature of phosphine through observations at 1 millimeter wavelength made with the James Clerk Maxwell Telescope (JCMT) in Hawaii, later confirmed with data from the Atacama Large Millimeter Array (ALMA) observatory in Chile. The resulting paper is lengthy and judiciously written, as witness:

If no known chemical process can explain PH3 within the upper atmosphere of Venus, then it must be produced by a process not previously considered plausible for Venusian conditions. This could be unknown photochemistry or geochemistry, or possibly life. Information is lacking—as an example, the photochemistry of Venusian cloud droplets is almost completely unknown. Hence a possible droplet-phase photochemical source for PH3 must be considered (even though PH3 is oxidized by sulfuric acid). Questions of why hypothetical organisms on Venus might make PH3 are also highly speculative…

And here again, the note that what we are talking about is unusual chemistry:

Even if confirmed, we emphasize that the detection of PH3 is not robust evidence for life, only for anomalous and unexplained chemistry. There are substantial conceptual problems for the idea of life in Venus’s clouds—the environment is extremely dehydrating as well as hyperacidic. However, we have ruled out many chemical routes to PH3

Image: Artist’s impression of Venus, with an inset showing a representation of the phosphine molecules detected in the high cloud decks. Credit: ESO / M. Kornmesser / L. Calçada & NASA / JPL / Caltech. Licence type Attribution (CC BY 4.0).

Phosphine is a rare molecule, one that is made on Earth through industrial methods, although microbes that live in environments without oxygen can likewise produce it when phosphate is drawn from minerals or other sources and coupled with hydrogen. MIT researchers have previously investigated it as a potential biosignature, one of a great many studied by Sara Seager and William Bains that we’ll want to use in our investigations of exoplanet atmospheres. It’s clear, though, that no one expected to find it in the clouds of Venus. Greaves explains:

“This was an experiment made out of pure curiosity, really – taking advantage of JCMT’s powerful technology, and thinking about future instruments. I thought we’d just be able to rule out extreme scenarios, like the clouds being stuffed full of organisms. When we got the first hints of phosphine in Venus’ spectrum, it was a shock!… In the end, we found that both observatories had seen the same thing – faint absorption at the right wavelength to be phosphine gas, where the molecules are backlit by the warmer clouds below.”

The international team working on the phosphine detection has investigated everything from minerals drawn into the clouds from the surface to volcanes, lightning, even sunlight, but none of the processes examined made enough phosphine to account for the data. In fact, the abiotic methods could produce at best one ten thousandth of the amount found in the telescope data.

But what a tough place for life to persist given an atmosphere where the high clouds are about 90 percent sulphuric acid. The hostility of the Venusian environment doubles down on the question of whether there are abiotic processes we have yet to consider. Following up on the phosphine detection, a new paper from the MIT researchers homes in on the matter:

(Greaves et al. 2020) have reported the candidate spectral signature of phosphine at altitudes >~57 km in the clouds of Venus, corresponding to an abundance of tens of ppb [parts per billion]. It was previously predicted that any detectable abundance of PH3 in the atmosphere of a rocky planet would be an indicator of biological activity (Sousa-Silva et al. 2020). In this paper we show in detail that no abiotic mechanism based on our current understanding of Venus can explain the presence of ~20 ppb phosphine in Venus’ clouds. If the detection is correct, then this means that our current understanding of Venus is significantly incomplete.

Image: This artistic impression depicts Venus. Astronomers at MIT, Cardiff University, and elsewhere may have observed signs of life in the atmosphere of Venus. Credit: ESO (European Space Organization)/M. Kornmesser & NASA/JPL/Caltech.

And from MIT co-author Clara Sousa-Silva, who examined phosphine as an exoplanet biosignature in a paper earlier this year, a look at the broader implications:

“A long time ago, Venus is thought to have oceans, and was probably habitable like Earth. 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.”

What a boon this finding will be to those interested in taking our eye off Mars for an astrobiological moment and looking toward the nearest terrestrial planet, for follow-up studies have to include one or more missions to Venus to study its atmosphere, perhaps including some kind of sampling and return to Earth. The MIT paper, Bains et al. as referenced below, includes both Seager and Sousa-Silva as co-authors, along with Cardiff’s Greaves, and bears a title that defines the issue: “Phosphine on Venus Cannot be Explained by Conventional Processes.”

Seager’s work on a wide range of potential biosignatures is definitive and has been examined before in these pages. Anyone interested in the broader question of how we go about defining a biosignature needs to get conversant with her “Toward a List of Molecules as Potential Biosignature Gases for the Search for Life on Exoplanets and Applications to Terrestrial Biochemistry,” Astrobiology, June 2016, 16(6): 465-485 (abstract).

So perhaps life, or perhaps a yet undiscovered mechanism for producing phosphine on Venus. Either way, the path forward includes an examination of a possible paradigm shift — the authors use this phrase — involving not just Venus but terrestrial planets in general. And I think we can assume that laboratory work on phosphorous chemistry is about to get a major boost.

The paper is Greaves et al., “Phosphine gas in the cloud decks of Venus,” Nature Astronomy 14 September 2020 (abstract). The MIT paper is Bains et al., “Phosphine on Venus Cannot be Explained by Conventional Processes,” submitted to Astrobiology – Special Collection: Venus (preprint). The Sousa-Silva paper on phosphine is “Phosphine as a Biosignature Gas in Exoplanet Atmospheres,” Astrobiology Vol. 20, No. 2 (31 January 2020). Abstract.


Comments on this entry are closed.

  • John Baccellieri September 15, 2020, 9:32

    Paul, as soon as I saw the phosphine story break yesterday, I came to Centauri Dreams to REALLY understand it, and to avoid the sensationalism. I read the Nature paper, but a lot of it was beyond my knowledge-level.

    Thanks for your work, helping us amateurs make sense of the Cosmos.

    • Paul Gilster September 15, 2020, 10:05

      What a kind thing to say! Thanks, John. I’m delighted the site is helpful and glad to have you aboard.

  • Michael Fidler September 15, 2020, 10:15


    New evidence suggests presence of potential biosignature on closest planet to Earth.

    San Francisco – September 15, 2020 – Breakthrough Initiatives, the privately-funded space science programs founded by science and technology investor and philanthropist Yuri Milner, are funding a research study into the possibility of primitive life in the clouds of Venus. The study is inspired by the discovery, announced yesterday, of the gas phosphine, considered a potential biosignature, in the planet’s atmosphere.
    The science team undertaking the research will comprise world-class physicists, astronomers, astrobiologists, chemists and engineers, led by Dr. Sara Seager, Professor of Planetary Science, Physics and Aerospace Engineering at the Massachusetts Institute of Technology. The group will investigate the scientific case for life and analyze the technical challenges of an exploratory mission in the event that such evidence proves compelling.

    Some food for thought:

    1. Venus super impact 700 million years ago causing the
    Cambrian explosion.

    2. The Snowball Earth from 775 to 717 million years ago may have been caused by the global oceans on Venus being blown into space by the comet or asteroid super impact.

    3. Could the Earth have been encircled with rings of material from super impacts on Venus 700 million years ago? This may be why the earth became a snowball because of the shadow of the ring from the Venus debris. This may be made of salt water and mud. the long term effect would be bring material from the impact on Venus to earths surface and atmosphere.

    4. Venus panspermia; If animal life such as sea worms was embedded in the material from Venus the remains would not be record till later because of the ice and scarring of earth surface by the world wide glaciers.

    5. Life on Venus may have returned after the impact and possibly evolved to survive in the upper atmosphere.

    6. What would be the effects of such a large impact and how orbital dynamics would transport material from the inner orbit of Venus to the earths orbit. The solar winds, flares and CME may also blast material from Venus to Earth.

    • Alex Tolley September 15, 2020, 12:10

      Rather Velikovskyian?

      It would be remarkable if the Venusian biota had identical biology to terrestrial biota, which it would have to if any fell to Earth and survived. This would imply a panspermia event and likely common origin for the life on both worlds. Given the current acidic nature of Venus atmosphere, could life have evolved a means to survive the very different environment of the oceans and teh clouds? Most likely the ocean to cloud hypothesis is a red herring. If there is life in Venus’ clouds, I would expect it to be more akin to the bacteria in earth’s clouds which have origins on the surface and are swept up. But on Venus, they would have to have evolved some form of protection from the acid. Grinspoon had suggested that the microbes reproduced and died quickly maintaining populations, back in 2018. Greaves notes that the atmosphere on Venus has a circulation model of sinking at the poles and rising at the equator. This implies that life would be drawn down to the hot depths and cooked, but the components needed would be drawn back up at the equator.
      While one interpretation is that this is life, it could also be that the equator is where the phosphine is produced, either at depth or by UV sunlight, and then degrated by the acid as it circulates back to the poles, as the data indicates.

      • Michael Fidler September 15, 2020, 23:42

        Well, I’m glad you lived before 700 million years ago, but put the earth were Venus is and what would end up with, earth panspermia to Venus. The original pre space age view of Venus was a tropical paradise and 700 to 800 years ago it may have well been that. Solar wind may have infected earth with early life and plants from oceans and land areas on Venus. I venture to guess that maybe the land areas were appearing later because of solar erosion of water being so close to the sun. The big question is when the super impact happened and as Nicky said no evidence of it, but resurfacing for 700 to 800 million years have would of wiped it out. What is needed is thousands of chip seismographs powered by diamond radioactive waste cells that land on Venus and last for years. This would give us a complete view of the interior and what may have happened in the past. The Russians have been way ahead of research and landers for Venus and launch opportunities come every 19 months with only a 4 month cruise. Hopefully more probes will be sent.

        Soviet Balloon Probes May Have Seen Rain on Venus.

        “Looking again at the old data Dorrington noticed that one of the balloons, from Vega 2, seemed to have reduced its leakage rate at some point, as if it had somehow repaired itself. “I thought that was funny,” he said.
        An alternative explanation for why the balloons descended would have been that they got heavier, most likely from a buildup of liquid on their outer surface. Sulfuric acid could have precipitated out of Venus’ clouds in a fine mist, coating the balloons and then slowly dripping off. In the case of the Vega 2 balloon, sensors indicated that at one point the probe’s buoyancy changed quickly, on the order of a minute, which could have happened when the balloon ran into a light drizzling shower.”
        “This work is credible and interesting, but speculative,” wrote planetary scientist Kevin McGouldrick of the University of Colorado, Boulder, who was not involved in the work, in an email to Wired.

        Maybe the Venusian life caught a ride on the balloon; “In the case of the Vega 2 balloon, sensors indicated that at one point the probe’s buoyancy changed quickly, on the order of a minute”

        • ljk September 16, 2020, 11:12

          Regarding interesting data from the Pioneer Venus drop probes, read the following quote taken from this page:


          “Some unexpected problems arose. All the temperature probes failed when sulphuric acid blocked the inlet. When it boiled off its constituents entered the instruments. The sensors did not physically break, acid films on the sensors were indicated from partial shorting of insulation while in the clouds, but this cleared as the probes descended into higher temperatures.

          “These anomalous events entered the engineering and science data at the same altitude in all four probes. Anomalies included power variations, changes in the Large Probe’s transponder static phase error and receiver AGC, jumps in internal pressure and temperature readings were probably due to static discharges inside or outside the probe.

          “One explanation suggested there was a reaction between the atmospheric sulphur and probe materials. Because each probe was always colder than the atmosphere, sulphur condensed on the outside of the probe pressure vessels and was carried down into the regions of higher temperatures. This generated an electrical charge. Each probe then acted as a large capacitor because parts of the probe had not been electrically bonded to avoid heat transfer. Also, titanium, though a tough material, is a poor conductor, so would act as an insulator and stop electrical charges from dissipating. One conclusion was that most of the anomalies could be explained by these unexpected electrical interactions.”

          Now for some other hopefully useful online documents in our quest to see if this phosphine finding leads anywhere…

          Venus Atmospheric Composition In Situ Data: A Compilation:


          This great NASA book on the PV missions is here in PDF format:


          There is also this relevant PV data document:

          The Pioneer Venus Orbiter: 11 years of data. A laboratory for atmospheres seminar talk


          Don Mitchell’s excellent site on the Soviet exploration of Venus:


      • Spaceman September 17, 2020, 18:20


        Let’s assume that the PH3 has an atmospheric microbial origin. What is your best guess as to whether these little guys would be the descendants of an independent abiogenesis event on Venus as opposed to descendants of Earth-based microbes that somehow hitched a ride to our sister planet? If the hypothetical Venetian microbes were from an independent genesis, then what would this tell us, from a statistical perspective, about how common at least microbial life may be in the Universe?

        • Alex Tolley September 17, 2020, 22:07

          If there is Venusian life and it is from a unique biogenesis independent from earth, then I would say that this makes the probability that life is common in the universe as very high, as it indicates that life does arise wherever conditions are favorable.

          Unless it turns out that we are unlucky and this hypothetical life is hard to disambiguate between single or different biogeneses, then we will have an example of a different biology and double the examples of the biological space life can take. The value to industry is likely to be high, making a sample return worth the cost if there is sufficient evidence that life does exist.

          • Michael Fidler September 22, 2020, 9:49

            Yes I’m sure the industrial military complex would love a hard shell, molecular acid for blood kind of aliens!

    • Nicky September 15, 2020, 14:18

      Recent studies have found an increased impact flux since Phanerozoic, which implies that the Venus surface age (calculated from size-frequency) is actually a lot younger than 700 Myr assumed back in the 1990s. More recent calculations place it around 200 Myr when Venus was resurfaced. Also we have no evidence in regard to a huge impact was the cause of resurfacing.

      • Michael Fidler September 18, 2020, 23:54

        Venus’ Ancient Layered, Folded Rocks Point to Volcanic Origin.
        September 17, 2020. (Or maybe sedimentary rocks!)

        “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.”
        “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.”


        Largest impact feature in the solar system is on Venus at over 8000 miles (13000 km) across.


    • Michael Fidler September 16, 2020, 0:03

      Venus: Will private firms win the race to the fiery planet?

      “The company’s CEO, Peter Beck, is fascinated by Venus and has already announced his intention to send a mission there in 2023. He’s funding and constructing it in-house.”
      “Peter Beck’s message is “give me a call. If anybody wants to join the team, come join us. But, you know, the bus is leaving; we’re going!”

      “BREAKTHROUGH INITIATIVES” should get together with them!

      • Michael Fidler September 16, 2020, 9:47

        Potential biosignature discovery could boost prospects of Venus missions.

        “Beck said he was assembling a “pretty amazing” science team, but did not disclose with whom he was working. At the RAS briefing, Seager said she had been in discussions with Beck about a Venus mission. The spacecraft, she said, would weigh only about 15 kilograms, of which 3 kilograms would be available for a science payload. “We have to work hard to make sure an instrument that would be useful for the search for life will fit into that payload,” she said. “We’re really looking forward to it.”

        So maybe they already have!

  • ljk September 15, 2020, 10:26

    Did the Vega aerostats placed in the Venusian atmosphere by the Soviets as part of their Vega-Halley mission in 1985 detect anything that might be interpreted differently now in support of this new announcement?

    Maybe I just missed it but I have not seen any mention yet about the only balloon probes sent to Venus. Note how the second link below says the Vega balloons may have detected rain. What else might they have found that we initially missed?






    A detailed article on plans to get more probes to Venus. At least now they have no excuse not to be attuned to finding life signs:


    As for America’s only attempt so far to directly explore Venus’ atmosphere using the four drop probes from the Pioneer Venus mission in 1978, if I remember correctly all four probes reported an increase in infrared radiation before those sensors were overloaded. Is there any correlation there? Did the PV mission detect anything we might interpret differently now?



    • Alex Tolley September 15, 2020, 12:19

      I was completely unaware of these earlier missions. Both teh Vega and Pioneer missions had mass spectrometers, yet I don’t see any indication that they detected anything special. Do you have any data on the results to determine if they even detected the phosphine gas as one would expect if they were sensitive enough?

      • ljk September 16, 2020, 10:44

        Not that I am aware of, nor will I pretend to you that I did an exhaustive search, either. However, this link that I also provided above has access to most if not all of the atmospheric data from the Pioneer Venus mission:


        Most of the Venera landers were also designed to sample the planet’s atmosphere as they descended through it. If anyone knows where a nice one-stop-shopping spot or spots for their data might exist, please let us know.

        Venus has lightning in its atmosphere. It also has many active volcanoes. Both are ingredients for supporting life, at least high in the atmosphere or deep underground. Just saying.

  • Michael Fidler September 15, 2020, 10:39

    Feasibility Analysis and Preliminary Design of ChipSat Entry for In-situ Investigation of the Atmosphere of Venus.

    “Recent miniaturization of electronics in very small, low-cost and low-power configurations suitable for use in spacecraft have inspired innovative small-scale satellite concepts, such as ChipSats, centimeter-scale satellites with a mass of a few grams. These extremely small spacecraft have the potential to usher in a new age of space science
    accessibility. Due to their low ballistic coefficient, ChipSats can potentially be used in a swarm constellation for extended surveys of planetary atmospheres, providing large amounts of data with high reliability and redundancy. We present a preliminary feasibility analysis of a ChipSat planetary atmospheric entry mission with the purpose of
    searching for traces of microscopic lifeforms in the atmosphere of Venus. Indeed, the lower cloud layer of the Venusian atmosphere could be a good target for searching for microbial lifeforms, due to the favourable atmospheric conditions and the presence of micron-sized sulfuric acid aerosols. A numerical model simulating the planetary entry of a spacecraft of specified geometry, applicable to any atmosphere for which sufficient atmospheric data are available, is
    implemented and verified. The results are used to create a high-level design of a ChipSat mission cruising in the Venusian atmosphere at altitudes favorable for the existence of life. The paper discusses the ChipSat mission concept and considerations about the spacecraft preliminary design at system level, including the selection of a potential


    Hmm, sounds like something is working towards a chip powered probe for Venusian life…

    • ljk September 15, 2020, 12:01

      Lots of little smart probes are the future of deep space exploration.

      To show just how much the paradigm of crewed versus unmanned space vessels has changed in the past four decades, read the following from this link of an interview with Dr. Sara Seager, an astrophysicist and planetary scientist at the Massachusetts Institute of Technology (MIT), discussing who, what, and how a suitably advanced species would best move through interstellar space:


      “My personal opinion about life that could traverse the galaxy, if we are now talking about life that could come to Earth, or in the future, if we’re able to travel to a distant star system, is that it probably has to be nonbiological because space is very harmful for people. We can barely survive on Earth, if you think about it, and Earth is a very safe, well-designed place for us, or rather we are adapted to our environment. So I think for us initially as human beings to find life elsewhere, it’s bound to be biological, since that’s all we can see; it’s all we know how to do. But if we ever think of traveling through the galaxy or of alien life coming here, then I believe on a personal level that it will be nonbiological.”

  • ljk September 15, 2020, 10:54

    Carl Sagan predicted life on Venus in 1967. We may be close to proving him right.


    13 HOURS AGO


    To quote:

    So it was all the more surprising when Sagan co-authored a paper proposing we might still one day find microbial life above our sister planet. “If small amounts of minerals are stirred up to the clouds from the surface, it is by no means difficult to imagine an indigenous biology in the clouds of Venus,” he wrote in Nature in 1967 — two years before NASA landed on the moon. “While the surface conditions of Venus make the hypothesis of life there implausible, the clouds of Venus are a different story altogether.”

    As Sagan pointed out, a high carbon-dioxide atmosphere was no obstacle. Up at the 50km (31-mile) layer, at the top of Venus’ clouds, conditions are actually hospitable and almost Earth-like. Organisms could thrive in the upper reaches the same way bacteria thrives around superheated, CO2-rich vents at Yellowstone. Add sunlight and water vapor to CO2, he said, and you have the recipe for that building block of life, photosynthesis.

    “Sagan’s work on Venus was formative, though few today remember his impact,” says Darby Dyar, the chair of NASA’s Venus Exploration Advisory Group. “His idea was prescient, and still makes sense today: between the hellish surface conditions on present-day Venus and the near-vacuum of outer space must be a temperate region where life could live on.”

    Just 11 years after Sagan made his prediction, another Venus probe discovered methane in the atmosphere — which could be considered a predictor of the presence of organic material. Scientists like Sagan were cautious about the discovery; no one could prove methane meant life beyond a reasonable doubt. (We also found it on Mars in 2018, and have yet to explain that). Still, no one ever gave a reasonable alternative for why the methane might be hanging around on Venus.

    Here is another paper by Sagan from 1971 titled The Trouble with Venus:


  • Alex Tolley September 15, 2020, 11:56

    I also recommend the BBC’s “Sky at Night” episode that was a a prepublication exclusive interview with Greaves and Bains. Bains was particularly informative about the issues of life surviving in a sulfuric acid atmosphere and showed that terrestrial plants with waxy cuticles can withstand the extremely corrosive effect of the acid.

    The question however is that this sort of protection must be available for bacterial organisms that can float in the clouds (unless there is some complex plant or animal that has gas bags to do the same).

    The first issue is experimental – is teh signal and artifact or some sort of algorithm error? I think the team have done a lot of work to eliminate both, but follow up is necessary.
    Is the identification in error? So far they seem to have eliminated other compounds, but this is where I might be concerned – a misidentification. But again, so far no one has indicated this is a likely error.
    Bains was careful to not rule out some form of abiotic chemistry, but maybe there is a route that they missed. What is important is that phosphine is rapidly degraded by sulfuric acid, so it must be produced copiously. The assumption is biotic production, but this is a Sherlock Holmes deduction “After eliminating the impossible….”.

    If it is life, the atmosphere must be preventing and sinks for key biological elements. Carbon is not a problem, nor sulfur. But what about other needed elements? A sink could slowly wind down the resource. On Earth, phosphorus is one such element that is limiting. Would it be the same on Venus, requiring some sort of injection of new material to ensure that phosphine can be produced by hypothetical organisms?

    If nothing else, this finding should invigorate studies of the Venusian atmosphere and chemisty, as well as possibly prioritizing a mission to the atmosphere to do some sampling of the material, including looking for other biosignatures.

  • Randy Chung September 15, 2020, 12:09

    The Venusian atmosphere has oxidized forms of sulfur (sulfur dioxide SO2 and sulfur trioxide SO3) as well as a reduced form (hydrogen sulfide H2S). Now phospine (PH3) has been found.

    I have read that no abiotic process has been found such as from lightning or sunlight, but what about hydrogen from the solar wind? That could provide a continuous effect of reducing both sulfur oxides and phosphorus oxides.

    • Alex Tolley September 15, 2020, 15:04

      The extended figure 7 of the paper include the reduction of phosphorus oxides with hydrogen. Unless the solar wind is increasing production by 4 orders of magnitude over their assumed production rates, then this route seems unlikely. Any mechanism also has to account for the change in PH3 signal strength from the equator (high) to the poles (not measurable) – wouldn’t the solar wind generate reactions at the poles too, albeit lower?

      • Randy Chung September 15, 2020, 20:01

        Well, they do mention the solar wind once, but dismiss its possible effects because they assume it’s impossible for the solar wind hydrogen to move down to the cloud height.

        Measurements taken over a number of years would be nice. If the phosphine level changes with the solar cycle, that would be interesting.

        And the phosphine level being undetectable at the poles doesn’t disprove the solar wind hypothesis. The collection of the solar wind *should* decrease with latitude. And if there’s a rate limited oxidation reaction, the amount of solar wind collection would have to be higher than the rate limit to become detectable.

        • Alex Tolley September 16, 2020, 11:22

          You are saying that since venus has no protective magnetic field, that solar protons might penetrate sufficiently to drive up the rates of PH3 production to mimic the levels claimed to be observed? Would other species in the upper atmosphere or clouds reacting with the protons also be present that are detectable by spectroscopy also be present to confirm or falsify this hypothesis?

        • Andrei September 22, 2020, 13:29

          @Randy Chung I think you’re on one possible right track there.
          The detected presence of small amounts of methane on Venus could also be created via such hydrogen as you suggest.

          Phosphine can also be created from volcanic sources, the process require a temperature of over 200C which indeed is found on Venus.

          Anyway I’d like to see the detection of Phosphine by a second science team, it’s a rule of thumb that any unusual detection should been done by more than one research group before it’s treated as fact.

  • Michael Way September 15, 2020, 13:18

    The reason they haven’t found any abiotic means for Venus is probably because… they didn’t look very hard and they didn’t talk to people who have studied these things for years. Note that there is not a single Venus person on these papers. Today David Catling mentioned some abiotic routes they did not consider, and I’m sure others will come about. Then there are problem with the data analysis, claiming 15 sigma detections in the abstract and showing 1 sigma in the plots of the main paper, the way they deal with the line broadening, the wings, etc. More than one person has pointed out that one normally obtains lines at two different frequencies to try to confirm your candidate since there are so many overlapping lines. They didn’t wait for that observation. I think this may be a great motivator for future Venus in-situ exploration, but I’m not convinced by these papers that this is life or even a detection of PH3. But now people are busy thinking harder about this, and we can hope for some follow up results in the coming year or years.

    • Alex Tolley September 15, 2020, 16:15

      Do you have a link for the Catling critique? I cannot find one on Google.

      • Robin Datta September 15, 2020, 21:28

        Would any of this be helpful?

        • Alex Tolley September 16, 2020, 13:24

          Thank you for trying. Those are the same references I found. However only the Forbes article may be relevant but I refuse to whitelist a business magazine for science opinions.

    • Michael Way September 18, 2020, 10:12

      My initial criticisms were mostly misplaced. It came from only reading the main Nature Astronomy paper. To fully understand their approach one MUST also read the Supplementary Materials and the recently submitted Astrobiology paper (https://arxiv.org/abs/2009.06499). Note that the title of the latter may seem a bit provocative, but reading it through the word “Conventional” takes on an important meaning.
      There are a number of supporting papers to consider as well before criticizing fully:

      This in some ways points to the poor formatting of journals like Nature Astronomy. We are past the days of print editions. Let’s go to a normal journal format so that we can get away from hiding much of the relevant information in the Supplementary Materials, while also putting many of the important figures in odd places (often at the end) rather than embedded with the text.

  • Dave Moore September 15, 2020, 15:03

    Recent papers have suggested that Venus could have habitable until 2 billion years ago. If this is the case, then Venus could quite easily had life on it–even if only through bolide transfer from Earth.

    As Venus entered its full greenhouse phase, it would have snuffed out its lifeforms with the remainder having to adapt to more and more extreme environments until now the last species cling on in the sulphuric acid clouds.

    So the idea seems quite probable.

    • Mike Serfas September 15, 2020, 15:49

      That’s a good point, and it suggests an interesting experiment. With most missions to search for life, we have to assume it has a completely unknown biochemistry. But if Venus life descends from Earth, even billions of years ago, it should have ribosomes and ribosomal RNA and be amenable to a simple environmental PCR survey.

      If a larger body of genetic sequence could be read and the data transmitted back to Earth, this information could likely be used right away to synthesize new enzymes – of immense and immediate value to industry.

      • Dave Moore September 16, 2020, 13:41

        I just had another thought on this matter. The environment of this postulated Venus lifeform is an anoxic, CO2 saturated, sulphuric solution, which is similar to certain volcanic springs here on earth. A search of such springs might turn up an analog.

  • Nicky September 15, 2020, 15:04

    The fact that many scientists act so much more aggressive (“teach astrobiologists chemistry”, “phosphine shitstorm”) towards PH3-life association on Venus than seasonal CH4-life association on Mars is probably that it is so much more conceivable if life had existed on Mars than on Venus.

    Despite 20ppb PH3 is making a much stronger case than seasonal methane, the conceivability of life is so much lower on Venus that possibly a taboo is forming around this topic now.

  • Alex Tolley September 15, 2020, 15:30

    I’m trying to dig through some of the findings from the Venus missions, especially the Vega ballons. It seems that phosphorus was detected, but assumed to be H2PO3. None reported PH3 as expected as this is a novel detection.

    But given the instruments used, why has PH3 not been detected previously? Both spectra and mass spectrometry have been used, yet neither resulted in a reported detection of PH3. Is this due to better instruments or simply looking for the nonobvious?

    Previous missions have detected an unspecified absorbtion of UV light, attributed to particles if undetermined composition. If organic, that would be interesting.

    What interests me is what instruments would we deploy on a probe that would confirm the detection of PH3 in the atmosphere given apparent past failures, and extend the data to try to detect other biosignature molecules or even organisms, much like the plume experiments for Europa that are planned.

  • Mike Serfas September 15, 2020, 15:38

    One aspect I’m curious about is the equilibrium with PH4+ … my understanding is that phosphine is remarkably resistant to protonation, such that PH4+ might have a pH of -14 or so. But Venus’ atmosphere is something akin to fuming sulfuric acid … I haven’t tracked down what its effective pH might be estimated to be. I have no idea how it would be reaching this environment as a salt, but can we rule it out?

  • charlie September 15, 2020, 15:53

    abiotic process generating phosphine :

    Preparation and occurrence
    Phosphine may be prepared in a variety of ways.[10] Industrially it can be made by the reaction of white phosphorus with sodium or potassium hydroxide, producing potassium or sodium hypophosphite as a by-product.

    3 KOH + P4 + 3 H2O → 3 KH2PO2 + PH3
    Alternatively, the acid-catalyzed disproportioning of white phosphorus yields phosphoric acid and phosphine. Both routes have industrial significance; the acid route is the preferred method if further reaction of the phosphine to substituted phosphines is needed. The acid route requires purification and pressurizing. It can also be made (as described above) by the hydrolysis of a metal phosphide, such as aluminium phosphide or calcium phosphide. Pure samples of phosphine, free from P2H4, may be prepared using the action of potassium hydroxide on phosphonium iodide (PH4I).

    Laboratory routes
    It is prepared in the laboratory by disproportionation of phosphorous acid[11]

    4 H3PO3 → PH3 + 3 H3PO4
    Phosphine evolution occurs at around 200 °C. Alternative methods involve the hydrolysis of aluminium phosphide, calcium phosphide, and tris(trimethylsilyl)phosphine.

  • JONATHAN QUINN September 15, 2020, 16:44

    Here’s a related New Scientist article from 2002 discussing the observation of other chemicals in disequilibrium in Venus’ atmosphere (carbon monoxide, hydrogen sulphide and carbonyl sulphide) which are also difficult to explain: https://www.newscientist.com/article/dn2843-acidic-clouds-of-venus-could-harbour-life/

    • Alex Tolley September 15, 2020, 20:29

      Good catch. Also, I think that André Brack quoted in the article is wrong:

      “For life, you need a volume of water, not just tiny droplets.”

      We know that bacteria are alive in terrestrial clouds and even into teh stratosphere. They are important as seeds to start droplet formation. Whatever the objections to Schulze-Makuch’s hypothesis may be, I don’t believe Brack’s objection is valid any longer.

  • Geoffrey Hillend September 15, 2020, 17:06

    The phosphine may have come from an ocean and water over two billion years ago when Venus was still in the life belt since the Sun was a considerable percent less bright in the distant past. There could be phosphine deep inside the crust which is rereleased through volcanism.

    The phosphine in Venus atmosphere can’t be made today by life because there is no place life could exist for long there. Life would not stay at the same altitude in Venus atmosphere with the right temperature because of the Hadley type convention cells which would cause the air to move up too high drop back down lower into a too hot area, but that does not matter anyway because there is very little water vapor in Venus atmosphere which makes it impossible for life to live there or phosphine to be made. I have to conclude that the phosphine was made long ago when Venus had water and oceans which have long since evaporated from the increased brightness of the Sun over time. Phosphine on Earth has to be dissolved with water first to be released from the rocks before it can be used by life or plants in the water and “phosphine cycles.”

    • Mike Serfas September 16, 2020, 4:46

      The Hadley cell was a nagging question in my mind — looking at https://www.lpi.usra.edu/vexag/chapman_conf/presentations/limaye.pdf it appears that unlike Earth which has three, Venus has just one set of convection cells going all the way from equator to pole. I would have thought that life swept to the poles would be checkmated, since it has to return at lower altitude … but according to the graphic on page 4 (I ought to track down Goldstein, 1989) the return from pole to equator is still above 70 km — if anything, still a little chilly! On the other hand Wikipedia’s article adds some material about a lower Hadley cell, cold polar collars at 60-70 degrees latitude with (continual?) upwelling of adiabatically cooled air, clouds at 72 km, also the polar vortex … it turns out the science of another planet’s atmosphere isn’t that easy for a non-meteorologist to work out. :) But the scientists at the press conference thought life could survive in the planet’s circulation, and from a first glance at what’s known it seems more plausible than I’d have imagined.

      • Mike Serfas September 16, 2020, 12:20

        Well, if my goal was to suggest I had more to learn about the meteorology the above accomplished it… the first cell I was looking at was between day and night sides of the planet and shouldn’t be confused with a Hadley cell. Nonetheless, there are routes by which suspended organisms could escape searing heat, perhaps often enough to allow their propagation.

  • Eniac September 15, 2020, 17:28

    Great article, Paul!
    It will be good to see some more interest in Venus, going forward, if only to honor and finally catch up with the heroic efforts of Soviet scientists and engineers of the Venera and Vega projects in the seventies and eighties.
    I believe it is unlikely that we will see a sample return, though, as that would require bringing a full sized rocket to Venus. The much lower escape velocities of the moon and even Mars make a return plausible, but Venus is well beyond reach in my opinion.

  • Thomas R Mazanec September 15, 2020, 19:22

    An abiotic source of phosphine would likely be as exotic as exolife, something like the way LGM-1 turned out to be the first neutron star.

  • Scott Guerin September 15, 2020, 19:30

    I’m always bothered by the adjectives that describe life as surviving, even thriving, in unimaginably “tough” environments. Those critters know nothing other than their environment which, akin to our 1atm, ~70°F habitant is often a pleasant, sometimes not, always variable, survivable ecotone. In fact, I think they are geniuses in their environment. Venusian microbes — or life anywhere if it exists — are no doubt sturdy enough to survive the pH levels, pressure, radiation levels, chemistry etc. they evolved in; a “tough environment” is relative. As either Wainwright or LL Bean said “there’s no such thing as bad weather, only unsuitable clothing.” In astrobiology, this might be recast as “there’s no such thing as a tough environment, only unsuitable genes.” And not to beat a dead microbe, but if you drag a Snailfish up from 26,000 feet below the surface of the ocean where it is in equilibrium, it will find our environment “tough.”

  • Robin Datta September 15, 2020, 21:17

    The Cool Worlds video by David Kipping on the subject, and the Event Horizon video by John Michael Godier.

    It migth seem that one or more of the Three Chinese Curses are operative:
    May you live in interesting times
    May you be recognized by people in high places
    May you find what you’re looking for

  • Ronald September 16, 2020, 2:22

    Isn’t the real problem on Venus the extreme lack of water, also in its atmosphere (as G. Hillend also remarks)? Hence, making a biotic cycle unlikely.
    But ‘fossil’ phosphine remaining from very early Venusian life would be almost as great a discovery.
    The question is: can phosphine of early biotic origin stay in the Venusian atmosphere this long>

  • Kamal Ali September 16, 2020, 10:34

    We should do a sample return from the Venusian atmosphere. It’s time to stop using indirect means and just go for the jugular. And that also applies to the Europan and Enceladus atmospheres.

  • Alex Tolley September 16, 2020, 11:05

    But are any of these starting compounds and the reaction conditions present on Venus, even at or below the surface. For example, your first reaction requires pure, white phosphorus. On Earth, this has to be extracted from phosphorus containing compounds. Perhaps the hot conditions on Venus will allow phosphorus to be separated.

    What your argument does suggest is that the PH3 probably originated below the clouds. As with Geoffrey Hillend’s suggestion of fossil PH3, the origin of the gas could be distinguished from biotic processes in the clouds by a sampling at various depths in the atmosphere. This might falsify the hypotheses of the various origin sources – cloud biotic or abiotic UV production vs production or fossil emissions at or below the surface. If atmosphere production was falsified, that would falsify the biotic hypothesis too.

  • ljk September 16, 2020, 11:25

    Apparently the Russians are now all worked up again to start exploring Venus, with some even claiming it is a “Russian planet”:



    Already they seem to be forgetting this joint mission plan with the US from just over one year ago:


  • charlie September 16, 2020, 12:31

    speaking of life:

    “Can life survive a star’s death? Webb telescope can reveal the answer”
    When stars like our sun die, all that remains is an exposed core—a white dwarf. A planet orbiting a white dwarf presents a promising opportunity to determine if life can survive the death of its star, according to Cornell University researchers.
    In a study published in the Astrophysical Journal Letters, they show how NASA’s upcoming James Webb Space Telescope could find signatures of life on Earth-like planets orbiting white dwarfs.

    A planet orbiting a small star produces strong atmospheric signals when it passes in front, or “transits,” its host star. White dwarfs push this to the extreme: They are 100 times smaller than our sun, almost as small as Earth, affording astronomers a rare opportunity to characterize rocky planets.

  • ljk September 16, 2020, 15:30

    In A Complete Fluke, A European Spacecraft Is About To Fly Past Venus – And Could Look For Signs Of Life

    Jonathan O’Callaghan

    September 16, 2020, 10:49 am EDT

    Earlier this week, scientists announced the discovery of phosphine on Venus, a potential signature of life. Now, in an amazing coincidence, a European and Japanese spacecraft is about to fly past the planet – and could confirm the discovery.

    On Monday, September 14, a team of scientists said they had found evidence for phosphine in the atmosphere of Venus. The region in which it was found, about 50 kilometers above the surface, is outside the harsh conditions on the Venusian surface, and could be a habitat for airborne microbes.

    To find out for sure, we will need to send a mission into the Venusian atmosphere to look for such life. Several proposals are on the table, with the closest being a spacecraft from the U.S. company Rocket Lab that could send a probe into the atmosphere as soon as 2023.

    Full article here:


    To quote:

    BepiColombo, launched in 2018, is on its way to enter orbit around Mercury, the innermost planet of the Solar System. But to achieve that it plans to use two flybys of Venus to slow itself down, one on October 15, 2020, and another on August 10, 2021.

    The teams running the spacecraft already had plans to observe Venus during the flyby. But now, based on this detection of phosphine from telescopes on Earth, they are now planning to use both of these flybys to look for phosphine using an instrument on the spacecraft.

    “We possibly could detect phosphine,” says ESA’s Johannes Benkhoff, BepiColombo’s Project Scientist. “But we do not know if our instrument is sensitive enough.”

    The instrument on the European side of the mission, called MERTIS (MErcury Radiometer and Thermal Infrared Spectrometer), is designed to study the composition of the surface of Mercury. However, the team believe they can also use it to study the atmospheric composition of Venus during both flybys.

    On this first flyby, the spacecraft will get no closer than 10,000 kilometers from Venus. That’s very far, but potentially still close enough to make a detection.

    “There actually is something in the spectral range of MERTIS,” says Jörn Helbert from the German Aerospace Center, co-lead on the MERTIS instrument. “So we are now seeing if our sensitivity is good enough to do observations.”

    As this first flyby is only weeks away, however, the observation campaign of the spacecraft is already set in stone, making the chance of a discovery slim. More promising is the second flyby next year, which will not only give the team more time to prepare, but also approach just 550 kilometers from Venus.

    “[On the first flyby] we have to get very, very lucky,” says Helbert . “On the second one, we only have to get very lucky. But it’s really at the limit of what we can do.”

    If a detection can be made, it would provide independent verification of the presence of phosphine in the atmosphere of Venus. And for future missions planning to visit the planet, which alongside Rocket Lab’s mission includes potential spacecraft from NASA, India, Russia, and Europe, that could be vital information.

    Even if the first flyby is unsuccessful in detecting phosphine, the team plan to use lessons learned to revise their observations for the second flyby. And it just might be that this mission, in a happy coincedence, could contribute to a major scientific discovery before it even reaches its intended target.

    “It’s kind of perfect timing,” says Helbert . “Now [the flyby] is even more exciting.”

  • ljk September 16, 2020, 16:43

    We need to go to Venus as soon as possible

    Answering questions about the possibility of life there will require not one but several new missions that can directly study the planet.

    by Neel V. Patelarchive

    September 16, 2020


  • Geoffrey Hillend September 16, 2020, 16:44

    There is also the idea of exotic photo chemistry, the abiotic phosphine produced by photo dissociation of molecules like hydrogen sulfide and chemical recombination which would need some phosphorus high in the atmosphere.

    I like Allex Tolley’s idea about measuring the chemistry at different altitudes. Another probe to Venus with a good mass spectrometer would work. We could land it in a deep crater and then use an x ray spectrometer to look at the rocks in the crater if it is possible to make an x ray spectrometer that won’t break in the high temperature and pressure on the surface of Venus. I don’t think a laser spectrometer like the one in Curiosity rover will be effective in such a thick atmosphere. Maybe we could increase the power or use a high frequency, ultra violet laser to burn rock and take the spectra of the sparks or light coming from the rock. The goal would be to get the spectra of a deep excavation with the hope that we could see any water bearing geology that proves there was running water or oceans in the past like calcite and hematite etc or sandstone. We also might find phosphine and phosphorus. It might also help us to know if the all of crust has been completely recycled so landing several probes in different locations, the craters and highlands to help us confirm our theories about the geology of Venus.

  • Patient Observer September 16, 2020, 21:40

    A scientific paper offered the conjecture that Venus had a habitable surface environment as recently as 200 million years ago (can’t find the link at the moment). As pure speculation, if life was present and evolved on Venus at a similar rate as on Earth, a complex ecological system, presumably with advanced plant and animal life, would have been present. Presumably some sort of fossil record may not be extant that could be discovered with suitable surface rovers.

    Said rovers could maintain a relatively cool internal environment through a combination of super insulation and mechanical refrigeration. Such refrigeration, working against a huge thermal gradient, would need a great deal of power. Where could that power come from? One possibility is via microwave power from several orbiting satellites or, if the winds permit, cables hung from balloons-born solar panels. Admittedly highly speculative but visually interesting.

    As a last bit of speculation, there would be a non-zero possibility that intelligent life may have evolved. That intelligent life may have visited Earth at a time when only single cell life forms existed. Having found it all rather boring, the Venusians decided to mix thing up a little and triggered the Cambrian explosion of life forms! Should be good enough for a sci-fi story.

    Sadly, I expect that the phosphine gas brouhaha to go the way of those martian meteorites but I want to believe…

  • Patient Observer September 16, 2020, 21:43

    Forgot to mention that upon learning of the discovery of phosphine gas in the Venusian atmosphere that may be a biosignature, my first thought was to check Centuri Dreams for the real lowdown. Was not disappointed!

    • Paul Gilster September 17, 2020, 6:20

      Thank you, Patient Observer!

  • Mike Serfas September 16, 2020, 22:15

    In 2003, Geoffrey Landis suggested that H2S in the atmosphere of Venus could be of biological origin ( https://web.archive.org/web/20110807004311if_/http://gltrs.grc.nasa.gov/reports/2003/TM-2003-212310.pdf ) because H2S should react with SO2. Here we are next door on the periodic table, same conundrum, same explanation.

    If life *were* generally hoarding hydrogen, might there be considerably more of the element hidden in the atmosphere of Venus than we imagine?

  • Michael Fidler September 17, 2020, 2:02

    What about the transits of Venus across the Sun? On June 8, 2004 and again on June 6, 2012 Venus transited the Sun and according to Wikipedia spectrographic studies where done of the atmosphere of Venus.

    Observation of the atmosphere of Venus simultaneously from Earth-based telescopes and from the Venus Express spacecraft. This gave a better opportunity to understand the intermediate level of Venus’s atmosphere than is possible from either viewpoint alone, and should provide new information about the climate of the planet.

    Spectrographic study of the atmosphere of Venus. The results of analysis of the well-understood atmosphere of Venus will be compared with studies of exoplanets with atmospheres that are unknown.

    The Hubble Space Telescope used the Moon as a mirror to study the light reflected from Venus to determine the makeup of its atmosphere. This may provide another technique to study exoplanets.

    So has has anyone looked for Phosphine in the results?


  • M September 17, 2020, 18:24

    The current conditions in the cloud cover of Venus would indeed be a very “tough place” for life to evolve. However, if the hypothetical lifeforms living in these clouds had descended from life that evolved on a much younger, and much more hospitable (from our perspective) Venus, then it would not be without precedent to suggest that this life could have evolved adaptive traits over the millions/billions of years since then that could allow such life to survive in the hellish conditions of the contemporary Venusian climate. We have seen on our own planet that life, once evolved, is incredibly robust. There are entire ecosystems sustained by sulfide vents in the abysmal depths of Earth’s oceans, a place where they must endure conditions not so terribly different from those in the Venusian cloud habitat, such as temperatures above the boiling point of water, extremely high pressure, and very high acidity (pH < 3 in some cases), to name a few. So, I personally do not find it to be such a far-fetched notion that some particularly hardy microbes could live quite comfortably in the Venusian cloudscape. Looking forward to watching this discovery unfold!

    • ljk September 21, 2020, 10:18

      If terrestrial creatures can live around geothermal vents in the deep ocean, or boiling hot sulfur springs, or under miles of solid rock, or in the water tanks of nuclear reactors, then I think the high clouds of Venus could be their version of the Bahamas in comparison.

  • Dmitri September 18, 2020, 8:10

    I want to join praising Paul Gilster in such exquisite work over the years turning Centauri Dreams to the site for no-nonsense information about space and interstellar matter that such breaking news like phosphine in the Venusian atmosphere make people check what is the opinion of other closely knowledgeable in the subject matter. Despite I’m no longer actively here I tend to turn back for good reading and checking the comments.

    Although I’m in believe this is result of living organisms I remind myself all such news in the past have turned out to be explained by natural processes that we weren’t aware of. Take the discovery of pulsars and the notion it’s Little Green Men, thus LGM-1 designation to very first such discovery.

    On lighter tone I would like to greet our Venusian overlords, microbial or not.

    • Paul Gilster September 18, 2020, 11:59

      Yes, it would be an interesting meeting! Thank you, Dmitri, for the kind words. I’m glad you’ve found the site useful and I’ll try to keep it that way.

  • Michael September 19, 2020, 12:38

    I think the phosphine could come from a phosphine telluride reaction, tellerium is suspected of building up around volcanoes due to the tempeture been about right forming the gas phosphine.

  • ljk September 21, 2020, 13:09

    If there is life on Venus, how could it have got there? Origin of life experts explain

    September 20, 2020 3.42pm EDT


  • ljk September 21, 2020, 14:08

    Bacteria on the ISS survive the perils of space for three years

    Three years in space wasn’t enough to kill a hardy radiation-resistant bacterium, suggesting bacteria may be able to travel between planets.

    Jackson Ryan

    Aug. 27, 2020 1:00 a.m. PT


    Again, we humans may think of Venus as a form of hell for life, but for some organisms it may contain enough of the ingredients to maintain certain creatures in relative comfort long enough to keep reproducing. We are only just starting to figure this out.

  • ljk September 22, 2020, 10:39

    SEPTEMBER 21, 2020

    EPSC2020: Parker Solar Probe, Akatsuki and Earth-bound observers give rare top-to surface glimpse of Venus

    Akatsuki observations of Venus at the time of the Parker Solar Probe flyby. These observations sampled the upper atmosphere at roughly 70 km altitude above the surface. Credit: JAXA, Planet-C

    Observations of Venus by NASA’s Parker Solar Probe, JAXA’s Akatsuki mission and astronomers around the world have given a rare cloud-top-to-surface glimpse of the Earth’s neighbouring planet. The results are being presented this week at the Europlanet Science Congress (EPSC) 2020, which is taking place as a virtual meeting from 21 September – 9 October.

    On 11 July 2020, the Parker Solar Probe, which is travelling to the inner Solar System to catch particles of the outer atmosphere of the Sun, completed the third of a series of flybys of Venus. From 19 June to 18 July, astronomers and members of the Akatsuki science team joined forces to support the probe’s encounter through a coordinated campaign of observations. The ground-based observations were contributed largely by amateur astronomers.

    A similar campaign will be carried out to support the flyby of Venus by ESA’s BepiColombo mission on 15 October 2020.

    “The campaign has resulted in multiple, multi-level observations right from the surface to the cloud-tops and airglow phenomena, which have given us unique insights into Venus’s atmosphere,” said Ricardo Hueso, a former member of ESA’s Venus Express mission and coordinator of the amateur participation. “The opportunity to observe Venus with so many instruments and with such a large collaboration means that we can enhance the scientific value of these short visits by the Parker Solar Probe and BepiColombo to Venus.”

    Full article here:


  • ljk September 25, 2020, 10:37

    A Precursor Balloon Mission for Venusian Astrobiology [IMA]


    The paper here:


    [Submitted on 24 Sep 2020]

    A Precursor Balloon Mission for Venusian Astrobiology

    Andreas M. Hein, Manasvi Lingam, T. Marshall Eubanks, Adam Hibberd, Dan Fries, William Paul Blase

    The recent detection of phosphine in the atmosphere of Venus has reignited interest in the possibility of life aloft in this environment. If the cloud decks of Venus are indeed an abode of life, it should reside in the “habitable zone” between ~50 to ~60 km altitude, roughly coincident with the middle cloud deck, where the temperature and pressure (but not the atmospheric composition) are similar to conditions at the Earth’s surface.

    We outline a precursor astrobiological mission to search for such putative lifeforms in situ with instrument balloons, which could be delivered to Venus via launch opportunities in 2022-2023. This mission would collect aerosol and dust samples on small balloons floating in the Venusian cloud deck and directly scrutinize whether they include any apparent biological materials and, if so, their shapes, sizes and motility.

    Our balloon mission would also be equipped with a miniature mass spectrometer that ought to permit the detection of complex organic molecules. The mission is augmented by contextual cameras that will be used to search for macroscopic signs of life in the Venusian atmospheric habitable zone.

    Finally, mass and power constraints permitting, radio interferometric determinations of the motion of the balloons in Venusian winds, together with in situ temperature and pressure measurements, will provide valuable insight into the poorly understood meteorology of the middle cloud region.

    Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Space Physics (physics.space-ph)

    Cite as: arXiv:2009.11826 [astro-ph.IM]
    (or arXiv:2009.11826v1 [astro-ph.IM] for this version)

    Bibliographic data

    Submission history

    From: Andreas M. Hein [view email]

    [v1] Thu, 24 Sep 2020 17:18:27 UTC (3,579 KB)


  • ljk September 29, 2020, 9:48


    [Submitted on 27 Sep 2020]

    Is Phosphine in the Mass Spectra from Venus’ Clouds?

    Rakesh Mogul, Sanjay S. Limaye, M. J. Way, Jamie A. Cordova Jr
    Considering the implications of the reported single spectral line detection of phosphine (PH3) by Greaves et al., we were inspired to re-examine data obtained from the Pioneer-Venus Large Probe Neutral Mass Spectrometer (LNMS) to search for evidence of phosphorus compounds. The LNMS obtained masses of neutral gases (and their fragments) at different altitudes within Venus’ clouds.

    Published mass spectral data correspond to gases at altitudes of 50-60 km, or within the lower and middle clouds of Venus – which has been identified as a potential habitable. We find that LMNS data support the presence of phosphine; although, the origins of phosphine remain unknown.

    Comments: <1200 words, 1 figure

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

    Cite as: arXiv:2009.12758 [astro-ph.EP]
    (or arXiv:2009.12758v1 [astro-ph.EP] for this version)

    Submission history

    From: Rakesh Mogul [view email]

    [v1] Sun, 27 Sep 2020 06:18:01 UTC (478 KB)


    Translation: The Pioneer Venus Large drop probe detected phosphine in the atmosphere of Venus back in December of 1978. Its origin is still unknown, however.

  • Laintal September 30, 2020, 4:04

    Hi Paul

    Yes this is super interesting and your updates are enjoyable reading.

    Here are a few links that may be of interest, I need to catch up on them too (wasn’t too well for a week when this news broke)


    Phosphine on Venus Cannot be Explained by Conventional Processes

    A Precursor Balloon Mission for Venusian Astrobiology

    Might active volcanisms today contribute to the presence of phosphine in Venus’s atmosphere?

    On The Biomass Required To Produce Phosphine Detected In The Cloud Decks Of Venus

    Authors: Manasvi Lingam, Abraham Loeb

    Feasibility Analysis and Preliminary Design of ChipSat Entry for In-situ Investigation of the Atmosphere of Venus

    Transfer of Life Between Earth and Venus with Planet-Grazing Asteroids

    Phosphine as a Biosignature Gas in Exoplanet Atmospheres

  • ljk October 15, 2020, 10:10


    [Submitted on 13 Oct 2020]

    Detection of simplest amino acid glycine in the atmosphere of the Venus

    Arijit Manna, Sabyasachi Pal, Mangal Hazra

    Amino acids are considered to be prime ingredients in chemistry, leading to life. Glycine is the simplest amino acid and most commonly found in animal proteins. It is a glucogenic and non-essential amino acid that is produced naturally by the living body and plays a key role in the creation of several other important bio-compounds and proteins.

    We report the spectroscopic detection of the presence of the simplest amino acid glycine (NH2CH2COOH) with transition J=13(13,1)–12(12,0) at ν=261.87 GHz (16.7σ statistical significance) with column density N(glycine)=7.8×1012 cm−2, in the atmosphere of the solar planet Venus using the Atacama Large Millimeter/submillimeter Array (ALMA).

    Its detection in the atmosphere of Venus might be one of the keys to understand the formation mechanisms of prebiotic molecules in the atmosphere of Venus. The upper atmosphere of Venus may be going through nearly the same biological method as Earth billions of years ago.

    Comments: 14 pages, 4 figures, submitted in Science

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Biological Physics (physics.bio-ph)

    Cite as: arXiv:2010.06211 [astro-ph.EP]
    (or arXiv:2010.06211v1 [astro-ph.EP] for this version)

    Submission history

    From: Sabyasachi Pal Dr. [view email]

    [v1] Tue, 13 Oct 2020 07:35:56 UTC (879 KB)


  • ljk October 16, 2020, 12:54


    [Submitted on 15 Oct 2020]

    A stringent upper limit of the PH3 abundance at the cloud top of Venus

    T. Encrenaz (1), T. K. Greathouse (2), E. Marcq (3), T. Widemann (1), B. Bézard (1), T. Fouchet (1), R. Giles (2), H. Sagawa (4), J. Greaves (5), C. Sousa-Silva (6) ((1) LESIA, Observatoire de Paris, PSL Université, CNRS, Sorbonne Université, Université de Paris, (2) SwRI, (3) LATMOS/IPSL, UVSQ Université Paris-Saclay, Sorbonne Université, CNRS, (4) Kyoto Sanyo University, (5) School of Physics and Astronomy, Cardiff University, (6) Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology)

    Following the announcement of the detection of phosphine (PH3) in the cloud deck of Venus at millimeter wavelengths, we have searched for other possible signatures of this molecule in the infrared range.

    Since 2012, we have been observing Venus in the thermal infrared at various wavelengths to monitor the behavior of SO2 and H2O at the cloud top. We have identified a spectral interval recorded in March 2015 around 950 cm−1 where a PH3 transition is present.

    From the absence of any feature at this frequency, we derive, on the disk-integrated spectrum, a 3-σ upper limit of 5 ppbv for the PH3 mixing ratio, assumed to be constant throughout the atmosphere. This limit is 4 times lower than the disk-integrated mixing ratio derived at millimeter wavelengths.

    Our result brings a strong constraint on the maximum PH3 abundance at the cloud top and in the lower mesosphere of Venus.

    Comments: Astronomy & Astrophysics, in press

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

    Cite as: arXiv:2010.07817 [astro-ph.EP]
    (or arXiv:2010.07817v1 [astro-ph.EP] for this version)

    Submission history

    From: Bruno Bézard [view email]

    [v1] Thu, 15 Oct 2020 15:11:37 UTC (805 KB)


  • ljk October 19, 2020, 13:38

    Portuguese astrophysicist Clara Sousa-Silva involved in possible discovery of life on Venus

    By Lurdes C. da Silva / O Jornal editor

    Posted Sep 24, 2020 at 5:19 PM

    “Understanding the heavens without having to go there… it’s like a super-power.”

    BOSTON – Clara Sousa-Silva was only 12 years old when she decided to become an astrophysicist, while watching a solar eclipse with her parents, who explained step-by-step what she was about to see and precisely at what time.

    “I could not believe that we, as a species, could predict the movement of the heavens like that,” she says. “I have always liked the idea of understanding the heavens without having to go there. It’s like a super-power… and I wanted it.”

    Today, the 33-year-old Porto native is a molecular astrophysicist at Massachusetts Institute of Technology (MIT) and a member of the international team of astronomers who recently discovered with powerful telescopes signs of what might be life in the clouds of the planet Venus.

    According to a study published last week in the journal Nature Astronomy, scientists at MIT, Cardiff University in Wales and other prestigious institutions detected the chemical phosphine near the top of the acidic clouds that blanket Venus. This rare molecule could be produced by living organisms.

    “I think discovering any potential bio signature on a habitable planet is very exciting. Discovering a biosignature on our nearest planet is even more exciting,” Sousa-Silva told O Jornal. “Finally, discovering phosphine on Venus, when phosphine has no known non-biological production pathways on rocky planets, is really, really significant.”

    Full interview here:


    To quote:

    In fact, her goal has been to find a habitable or inhabited planet by identifying every relevant molecule contributing to its biosphere. She uses quantum physics and computer calculations to create molecular “fingerprints” that allow scientists to detect remote gases on extrasolar planet atmospheres — particularly gases that are associated with life.

    “I have dedicated my career to phosphine and it is wonderful to see that work be useful for such a grand discovery,” Sousa-Silva said. “I like understanding how the molecules that life produces interact with light, and I love that we can detect that behavior from thousands and thousands of miles away.”

    Sousa-Silva arrived in the United States in 2016 to join MIT as a postdoc researcher. Last year, she became the co-director of the Harvard-MIT Science Research Mentoring Program. In this capacity, she organizes and manages an outreach program where high school students do a year-long independent research project under the guidance of astrophysics.

    She also enjoys being a science communicator, giving numerous lectures and presentations.

    “Science is only as good as the audience it reaches,” Sousa-Silva said. “I like feeling like I am contributing to making the scientific community more inclusive, and more interesting, and that’s why I enjoy science communication.”

    Sousa-Silva left Portugal at age 18 to pursue an integrated Bachelor’s and Master’s Degree in Physics and Astronomy at the Scotland University of Edinburgh.

    In 2015, she received a Ph.D. in Molecular Astrophysics from the University College London in the United Kingdom.

    “If we ever want to understand worlds beyond our own, we need to have access to a complex toolkit of data and models,” Sousa-Silva said. “It’s my goal to be able to unambiguously detect an alien biosphere from Earth, and without quantum chemistry that would be impossible.”

    But she will not jump to any conclusions when asked if someday we will be able to communicate with alien life forms.

    “Hah. No. Not in any relevant way,” Sousa-Silva said. “I believe life is inevitable and, if it happens on Earth, it likely happened elsewhere, but I don’t necessarily believe that intelligent alien life exists.”

    “Until we understand how we develop an advanced consciousness on Earth, I will not be attempting to figure out how common such life is in the universe,” she concluded.

    • Michael Fidler October 21, 2020, 3:38

      This group from the Netherlands is out to trash Dr. Clara Sousa-Silva quantum physics and computer calculations to create molecular “fingerprints” for phosphine in the clouds of Venus. Hmm…

      Re-analysis of the 267-GHz ALMA observations of Venus: No statistically significant detection of phosphine.


  • ljk January 5, 2021, 13:20

    Astrochemist brings search for extraterrestrial life to Center for Astrophysics

    Clara Sousa-Silva explores telltale biosignature gases on other planets

    BY Alvin Powell

    DATE January 4, 2021

    n September, a team of astronomers announced a breathtaking finding: They had detected a molecule called phosphine high in the clouds of Venus, possibly indicating evidence of life.

    That discovery shook the scientific establishment. Once thought of as Earth’s twin, Venus — though nearby and rocky — is now known to have a hellish environment, with a thick atmosphere that traps solar radiation, cranking surface temperatures high enough to melt metal, and accompanied by surface pressure akin to that thousands of feet below Earth’s ocean surface.

    But the detection, led by researchers from Cardiff University in Wales, the Massachusetts Institute of Technology, and the University of Manchester in England, was high in the atmosphere, where conditions are far more hospitable and the idea of microbial life more plausible. It was accomplished using spectroscopy, a method of determining the presence of different molecules in a planet’s atmosphere by analyzing how those molecules alter the light reflected from the planet.

    A key member of the team was fellow Clara Sousa-Silva, who had spent years studying the molecule’s spectroscopic signature and who believes that phosphine is a promising way to track the presence of extraterrestrial life.

    Sousa-Silva shifted her fellowship from MIT to the Center for Astrophysics | Harvard & Smithsonian and will spend the next two years advancing her work on biosignatures and life on other planets. She spoke with the Gazette about the recent discovery and what the future of the search for life may hold.

    Interview starts here:


    To quote:

    GAZETTE: Folks like you will be helping answer an interesting question in the decades to come: whether life is something rare or whether it’s not really that rare after all. It seems the thinking on that has been shifting in recent decades.

    SOUSA-SILVA: I do like that the shift is happening and that people are thinking that life is more common. I’m hoping that shift will go so far as thinking that life is not that special. It’s just an inevitable occurrence in a variety of contexts. If it can appear in places as different as Earth and Venus, which are at first glance similar because of their size and location but otherwise very different, then it must be extremely common because it would be the height of hubris to think that only the solar system can have life, but it has arisen twice in totally different environments.

    That seems really implausible. The sun is average, rocky planets are extremely common, the molecular cloud that formed the solar system was not special. Life on Earth came to be in a huge diversity of forms, and life changed Earth’s atmosphere many times. We only have one planet where we know life existed, but Earth has been many planets, which is something an astronomer colleague of mine, Sarah Rugheimer, likes to say. We have quite a lot of data points that basically show that life is pretty good at making itself happen in many ways throughout history.

  • ljk January 26, 2021, 22:10


    Complications In The ALMA Detection Of Phosphine At Venus

    Source: astro-ph.EP

    Posted January 26, 2021 12:23 AM

    Recently published ALMA observations suggest the presence of 20 ppb PH3 in the upper clouds of Venus. This is an unexpected result, as PH3 does not have a readily apparent source and should be rapidly photochemically destroyed according to our current understanding of Venus atmospheric chemistry.

    While the reported PH3 spectral line at 266.94 GHz is nearly co-located with an SO2 spectral line, the non-detection of stronger SO2 lines in the wideband ALMA data is used to rule out SO2 as the origin of the feature. We present a reassessment of wideband and narrowband datasets derived from these ALMA observations.

    The ALMA observations are re-reduced following both the initial and revised calibration procedures discussed by the authors of the original study. We also investigate the phenomenon of apparent spectral line dilution over varying spatial scales resulting from the ALMA antenna configuration. A 266.94 GHz spectral feature is apparent in the narrowband data using the initial calibration procedures, but this same feature can not be identified following calibration revisions.

    The feature is also not reproduced in the wideband data. While the SO2 spectral line is not observed at 257.54 GHz in the ALMA wideband data, our dilution simulations suggest that SO2 abundances greater than the previously suggested 10 ppb limit would also not be detected by ALMA. Additional millimeter, sub-millimeter, and infrared observations of Venus should be undertaken to further investigate the possibility of PH3 in the Venus atmosphere.

    Alex B. Akins, Andrew P. Lincowski, Victoria S. Meadows, Paul G. Steffes

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

    Cite as: arXiv:2101.09831 [astro-ph.EP] (or arXiv:2101.09831v1 [astro-ph.EP] for this version)

    Submission history

    From: Alex Akins

    [v1] Sun, 24 Jan 2021 23:59:10 UTC (2,018 KB)


    Astrobiology, Astrochemistry

  • ljk January 26, 2021, 22:16


    Claimed Detection Of PH3 In The Clouds Of Venus Is Consistent With Mesospheric SO2

    Source: astro-ph.EP

    Posted January 26, 2021 12:21 AM

    The observation of a 266.94 GHz feature in the Venus spectrum has been attributed to PH3 in the Venus clouds, suggesting unexpected geological, chemical or even biological processes.

    Since both PH3 and SO2 are spectrally active near 266.94 GHz, the contribution to this line from SO2 must be determined before it can be attributed, in whole or part, to PH3. An undetected SO2 reference line, interpreted as an unexpectedly low SO2 abundance, suggested that the 266.94 GHz feature could be attributed primarily to PH3.

    However, the low SO2 and the inference that PH3 was in the cloud deck posed an apparent contradiction. Here we use a radiative transfer model to analyze the PH3 discovery, and explore the detectability of different vertical distributions of PH3 and SO2. We find that the 266.94 GHz line does not originate in the clouds, but above 80 km in the Venus mesosphere.

    This level of line formation is inconsistent with chemical modeling that assumes generation of PH3 in the Venus clouds. Given the extremely short chemical lifetime of PH3 in the Venus mesosphere, an implausibly high source flux would be needed to maintain the observed value of 20±10 ppb.

    We find that typical Venus SO2 vertical distributions and abundances fit the JCMT 266.94 GHz feature, and the resulting SO2 reference line at 267.54 GHz would have remained undetectable in the ALMA data due to line dilution. We conclude that nominal mesospheric SO2 is a more plausible explanation for the JCMT and ALMA data than PH3.

    Andrew P. Lincowski, Victoria S. Meadows, David Crisp, Alex B. Akins, Edward W. Schwieterman, Giada N. Arney, Michael L. Wong, Paul G. Steffes, M. Niki Parenteau, Shawn Domagal-Goldman

    Comments: 12 pages, 5 figures, accepted to ApJL

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

    Cite as: arXiv:2101.09837 [astro-ph.EP] (or arXiv:2101.09837v1 [astro-ph.EP] for this version)

    Submission history

    From: Andrew Lincowski

    [v1] Mon, 25 Jan 2021 00:43:57 UTC (2,149 KB)


    Astrobiology, Astrochemistry

  • ljk March 25, 2021, 13:27