Possible Marker of Life Spotted on Venus

Authored by eso.org and submitted by blackswangreen
image for Possible Marker of Life Spotted on Venus

Possible Marker of Life Spotted on Venus

An international team of astronomers today announced the discovery of a rare molecule — phosphine — in the clouds of Venus. On Earth, this gas is only made industrially or by microbes that thrive in oxygen-free environments. Astronomers have speculated for decades that high clouds on Venus could offer a home for microbes — floating free of the scorching surface but needing to tolerate very high acidity. The detection of phosphine could point to such extra-terrestrial “aerial” life.

“When we got the first hints of phosphine in Venus’s spectrum, it was a shock!”, says team leader Jane Greaves of Cardiff University in the UK, who first spotted signs of phosphine in observations from the James Clerk Maxwell Telescope (JCMT), operated by the East Asian Observatory, in Hawaiʻi. Confirming their discovery required using 45 antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, a more sensitive telescope in which the European Southern Observatory (ESO) is a partner. Both facilities observed Venus at a wavelength of about 1 millimetre, much longer than the human eye can see — only telescopes at high altitude can detect it effectively.

The international team, which includes researchers from the UK, US and Japan, estimates that phosphine exists in Venus’s clouds at a small concentration, only about twenty molecules in every billion. Following their observations, they ran calculations to see whether these amounts could come from natural non-biological processes on the planet. Some ideas included sunlight, minerals blown upwards from the surface, volcanoes, or lightning, but none of these could make anywhere near enough of it. These non-biological sources were found to make at most one ten thousandth of the amount of phosphine that the telescopes saw.

To create the observed quantity of phosphine (which consists of hydrogen and phosphorus) on Venus, terrestrial organisms would only need to work at about 10% of their maximum productivity, according to the team. Earth bacteria are known to make phosphine: they take up phosphate from minerals or biological material, add hydrogen, and ultimately expel phosphine. Any organisms on Venus will probably be very different to their Earth cousins, but they too could be the source of phosphine in the atmosphere.

While the discovery of phosphine in Venus’s clouds came as a surprise, the researchers are confident in their detection. “To our great relief, the conditions were good at ALMA for follow-up observations while Venus was at a suitable angle to Earth. Processing the data was tricky, though, as ALMA isn’t usually looking for very subtle effects in very bright objects like Venus,” says team member Anita Richards of the UK ALMA Regional Centre and the University of Manchester. “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,” adds Greaves, who led the study published today in Nature Astronomy.

Another team member, Clara Sousa Silva of the Massachusetts Institute of Technology in the US, has investigated phosphine as a “biosignature” gas of non-oxygen-using life on planets around other stars, because normal chemistry makes so little of it. She comments: “Finding phosphine on Venus was an unexpected bonus! The discovery raises many questions, such as how any organisms could survive. On Earth, some microbes can cope with up to about 5% of acid in their environment — but the clouds of Venus are almost entirely made of acid.”

The team believes their discovery is significant because they can rule out many alternative ways to make phosphine, but they acknowledge that confirming the presence of “life” needs a lot more work. Although the high clouds of Venus have temperatures up to a pleasant 30 degrees Celsius, they are incredibly acidic — around 90% sulphuric acid — posing major issues for any microbes trying to survive there.

ESO astronomer and ALMA European Operations Manager Leonardo Testi, who did not participate in the new study, says: “The non-biological production of phosphine on Venus is excluded by our current understanding of phosphine chemistry in rocky planets' atmospheres. Confirming the existence of life on Venus's atmosphere would be a major breakthrough for astrobiology; thus, it is essential to follow-up on this exciting result with theoretical and observational studies to exclude the possibility that phosphine on rocky planets may also have a chemical origin different than on Earth.”

More observations of Venus and of rocky planets outside our Solar System, including with ESO’s forthcoming Extremely Large Telescope, may help gather clues on how phosphine can originate on them and contribute to the search for signs of life beyond Earth.

This research was presented in the paper “Phosphine Gas in the Cloud Decks of Venus” to appear in Nature Astronomy.

The team is composed of Jane S. Greaves (School of Physics & Astronomy, Cardiff University, UK [Cardiff]), Anita M. S. Richards (Jodrell Bank Centre for Astrophysics, The University of Manchester, UK), William Bains (Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, USA [MIT]), Paul Rimmer (Department of Earth Sciences and Cavendish Astrophysics, University of Cambridge and MRC Laboratory of Molecular Biology, Cambridge, UK), Hideo Sagawa (Department of Astrophysics and Atmospheric Science, Kyoto Sangyo University, Japan), David L. Clements (Department of Physics, Imperial College London, UK [Imperial]), Sara Seager (MIT), Janusz J. Petkowski (MIT), Clara Sousa-Silva (MIT), Sukrit Ranjan (MIT), Emily Drabek-Maunder (Cardiff and Royal Observatory Greenwich, London, UK), Helen J. Fraser (School of Physical Sciences, The Open University, Milton Keynes, UK), Annabel Cartwright (Cardiff), Ingo Mueller-Wodarg (Imperial), Zhuchang Zhan (MIT), Per Friberg (EAO/JCMT), Iain Coulson (EAO/JCMT), E’lisa Lee (EAO/JCMT) and Jim Hoge (EAO/JCMT).

An accompanying paper by some of team members, titled “The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere”, was published in Astrobiology in August 2020. Another related study by some of the same authors, "Phosphine as a Biosignature Gas in Exoplanet Atmospheres", was published in Astrobiology in January 2020.

The European Southern Observatory (ESO) is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

With a diameter of 15m (50 feet) the James Clerk Maxwell Telescope (JCMT) is the largest single dish astronomical telescope in the world designed specifically to operate in the submillimetre wavelength region of the electromagnetic spectrum. The JCMT is used to study our Solar System, interstellar and circumstellar dust and gas, evolved stars, and distant galaxies. It is situated in the science reserve of Maunakea, Hawaiʻi, at an altitude of 4092m (13 425 feet). The JCMT is operated by the East Asian Observatory on behalf of NAOJ; ASIAA; KASI; CAMS as well as the National Key R&D Program of China. Additional funding support is provided by the STFC and participating universities in the UK and Canada.

UK ALMA Regional Centre and University of Manchester

Leonardo Testi (contact for independent comment on the study)

Cell: +49 151 241 664 00

Connect with ESO on social media

my_name_is_______ on September 14th, 2020 at 16:46 UTC »

I desperately want it to be microbes. Extraterrestrial life is one of the things I want irrefutably scientifically confirmed in my lifetime.

I know life is probably everywhere in the universe in some form or another, but it's still huge that it's our next door neighbor!

There's so many interesting discoveries to be made just from these (potential) tiny microbes floating in the clouds.

Andromeda321 on September 14th, 2020 at 15:34 UTC »

Astronomer here! Here is what is going on!

For many years, astronomers have speculated that the most likely way to find evidence of extraterrestrial life is via biosignatures, which are basically substances that provide evidence of life. Probably the most famous example of this would be oxygen- it rapidly oxidizes in just a few thousand years, so to have large quantities of oxygen in an atmosphere you need something to constantly be putting it there (in Earth's case, from photoplankton and trees). Another one that's been suggested as a great biosignature is phosphine- a gas we can only make on Earth in the lab, or via organic matter decomposing (typically in a water-rich environment, which Venus is not). So, to be abundantly clear, the argument here is to the best of our knowledge you should only get this concentration of phosphine if there is life.

What did this group discover? Is the signal legit? These scientists basically pointed a submillimeter radio telescope towards Venus to look for a signature of phosphine, which was not even a very technologically advanced radio telescope for this sort of thing, but they just wanted to get a good benchmark for future observations. And... they found a phosphine signature. They then pointed another, better radio telescope at it (ALMA- hands down best in the world for this kind of observation) and measured this signal even better. I am a radio astronomer myself, and looking at the paper, I have no reason to think this is not the signature from phosphine they say it is. They spend a lot of time estimating other contaminants they might be picking up, such as sulfur dioxide, but honestly those are really small compared to the phosphine signal. There's also a lot on the instrumentation, but they do seem to understand and have considered all possible effects there.

Can this phosphine be created by non-life? The authors also basically spend half the paper going through allllll the different possible ways to get phosphine in the atmosphere of Venus. If you go check "extended data Figure 10" in the paper they go through all of the options, from potential volcanic activity to being brought in from meteorites to lightning... and all those methods are either impossible in this case, or would not produce you the concentration levels needed to explain the signature by several orders of magnitude (like, literally a million times too little). As I said, these guys were very thorough, and brought on a lot of experts in other fields to do this legwork to rule options out! And the only thing they have not been able to rule out so far is the most fantastic option. :) The point is, either we don’t get something basic about rocky planets, or life is putting this up there.

(Mind, the way science goes I am sure by end of the week someone will have thought up an idea on how to explain phosphine in Venus's atmosphere. Whether that idea is a good one remains to be seen.)

To give one example, It should be noted at this point that phosphine has apparently been detected in comets- specifically, it’s thought to be behind in the comet 67P/Churyumov-Gerasimenko by the Rosetta mission- paper link. Comets have long been known to have a ton of organic compounds and are water rich- some suggest life on Earth was seeded by comets a long time ago- but it’s also present in the coma of comets as they are near the sun, which are very different conditions than the Venusian atmosphere. (It’s basically water ice sublimating as it warms up in a comet, so an active process is occurring in a water-rich environment to create phosphine.) However, the amounts created are nowhere near what is needed for the amounts of phosphine seen in Venus, we do not have water anywhere near the levels on Venus to make these amounts of phosphine, and we have detailed radar mapping to show us there was no recent cometary impact of Venus. As such, it appears highly unlikely that what puts phospine into Venus’s atmosphere is the same as what puts it into a comet’s coma. Research into this also indicates that, surprise surprise, cometary environments are very different than rocky ones, and only life can put it in the atmosphere of a rocky planet.

How can life exist on Venus? I thought it was a hell hole! The surface of Venus is indeed not a nice place to live- a runaway greenhouse effect means the surface is hot enough to melt lead, it rains sulfuric acid, and the Russian probes that landed there in didn't last more than a few hours. (No one has bothered since the 1980s.) However, if you go about 50 km up Venus's atmosphere is the most Earth-like there is in the Solar System, and this is where this signal is located. What's more, unlike the crushing pressure and hot temperatures on the surface, you have the same atmospheric pressure as on Earth, temps varying from 0-50 C, and pretty similar gravity to here. People have suggested we could even build cloud cities there. And this is the region this biosignature is coming from- not the surface, but tens of km up in the pretty darn nice area to float around in.

Plus, honestly, you know what I’m happy about that will come out of this? More space exploration of Venus! It is a fascinating planet that is criminally under-studied despite arguably some of the most interesting geology and atmosphere there is that we know of. (My favorite- Venus’s day is longer than its year, and it rotates “backwards” compared to all the other planets. But we think that’s not because of the way it formed, but because some gigantic planet-sized object hit it in the early days and basically flipped it upside down and slowed its spin. Isn’t that so cool?!) But we just wrote it off because the surface is really tough with old Soviet technology, and NASA hasn’t even sent a dedicated mission in over 30 years despite it being literally the closest planet to us. I imagine that is going to change fast and I am really excited for it- bring on the Venus drones!

So, aliens? I mean, personally if you're asking my opinion as a scientist... I think I will always remember this discovery as the first step in learning how common life is in the universe. :) To be clear, the "problem" with a biosignature is it does not tell you what is putting that phosphine into the Venusian atmosphere- something microbial seems a good bet (we have great radar mapping of Venus and there are def no cloud cities or large artificial structures), but as to what, your guess is as good as mine. We do know that billions of microbes live high up in the Earth's atmosphere, feeding as they pass through clouds and found as high as 10km up. So I see no reason the same can't be happening on Venus! (It would be life still pretty darn ok with sulfuric acid clouds everywhere, mind, but we have extremophiles on Earth in crazy environments too so I can’t think of a good reason why it’s impossible).

If you want to know where the smoking gun is, well here's the thing... Hollywood has well trained you to think otherwise, but I have always argued that discovering life elsewhere in the universe was going to be like discovering water on Mars. Where, as you might recall, first there were some signatures that there was water on Mars but that wasn't conclusive on its own that it existed, then a little more evidence came in, and some more... and finally today, everyone knows there is water on Mars. There was no reason to think the discovery of life wouldn't play out the same, because that's how science operates. (This is also why I always thought people were far too simplistic in assuming we would all just drop everything and unite as one just because life was discovered elsewhere- there'd be no smoking gun, and we'd all do what we all are doing now, get on social media to chat about it.) But put it this way- today we have taken a really big first step. And I think it is so amazing that this was first discovered not only next door, but on a planet not really thought of as great for life- it shows there's a good chance life in some for is ubiquitous! And I for one cannot wait until we can get a drone of some sort into the Venusian atmosphere to measure this better- provided, of course, we can do it in a way that ensures our own microbes don't hitch a ride.

TL;DR- if you count microbes, which I do, we are (probably) not alone. :D

Edit: There will be a Reddit AMA Wednesday at noon EDT from the team at /r/askscience!

Edit 2: A lot of questions about whether this could just be from bacteria that hitched a ride on our old probes. The short answer is that's not really possible at the levels detected. Life as we have it on Earth can't survive on Venus because of all the sulfuric acid clouds and such. Even if something managed to do so, bacteria don't reproduce as fast as would be needed to explain this signal.

Not_Actually_French on September 14th, 2020 at 15:12 UTC »

I studied at Cardiff with the staff who made this discovery, and did my dissertation on the possibility of life on Venus. So excited that the research team there has found something so exciting, and hope it leads to more discoveries!