̽��ֱ�� of Cambridge - Paul Rimmer

Mysterious missing component in the clouds of Venus revealed

vb425 — Tue, 09 Jan 2024 10:05:24 +0000

What are the clouds of Venus made of? Scientists know they are mainly made of sulfuric acid droplets, with some water, chlorine, and iron. Their concentrations vary with height in the thick and hostile Venusian atmosphere. But until now they have been unable to identify the missing component that would explain the clouds’ patches and streaks, only visible in the UV range.

In a study published in Science Advances, researchers from the ̽��ֱ�� of Cambridge synthesised iron-bearing sulfate minerals that are stable under the harsh chemical conditions in the Venusian clouds. Spectroscopic analysis revealed that a combination of two minerals, rhomboclase and acid ferric sulfate, can explain the mysterious UV absorption feature on our neighbouring planet.

“ ̽��ֱ��only available data for the composition of the clouds were collected by probes and revealed strange properties of the clouds that so far we have been unable to fully explain,” said Paul Rimmer from the Cavendish Laboratory and co-author of the study. “In particular, when examined under UV light, the Venusian clouds featured a specific UV absorption pattern. What elements, compounds, or minerals are responsible for such observation?”

Formulated on the basis of Venusian atmospheric chemistry, the team synthesised several iron-bearing sulfate minerals in an aqueous geochemistry laboratory in the Department of Earth Sciences. By suspending the synthesised materials in varying concentrations of sulfuric acid and monitor the chemical and mineralogical changes, the team narrowed down the candidate minerals to rhomboclase and acid ferric sulfate, of which the spectroscopic features were examined under light sources specifically designed to mimic the spectrum of solar flares (Rimmer’s FlareLab; Cavendish Laboratory).

Researchers from Harvard ̽��ֱ�� provided measurements of the UV absorbance patterns of ferric iron under extreme acidic conditions, in an attempt to mimic the even more extreme Venusian clouds. ̽��ֱ��scientists are part of the newly-established Origins Federation, which promotes such collaborative projects.

“ ̽��ֱ��patterns and level of absorption shown by the combination of these two mineral phases are consistent with the dark UV-patches observed in Venusian clouds,” said co-author Clancy Zhijian Jiang, from the Department of Earth Sciences, Cambridge. “These targeted experiments revealed the intricate chemical network within the atmosphere, and shed light on the elemental cycling on the Venusian surface.”

“Venus is our nearest neighbour, but it remains a mystery,” said Rimmer. “We will have a chance to learn much more about this planet in the coming years with future NASA and ESA missions set to explore its atmosphere, clouds and surface. This study prepares the grounds for these future explorations.”

̽��ֱ��research was supported by the Simons Foundation, and the Origins Federation.

Reference:
Clancy Zhijian Jiang et al., ‘Iron-sulfur chemistry can explain the ultraviolet absorber in the clouds of Venus.’ Science Advances (2024). DOI:10.1126/sciadv.adg8826

Researchers may have identified the missing component in the chemistry of the Venusian clouds that would explain their colour and 'splotchiness' in the UV range, solving a longstanding mystery.

FreelanceImages/Universal Images Group/Science Photo Library via Getty Images

Sunrise over Venus

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Explore life in the Universe with new postgraduate programme

lw355 — Mon, 18 Sep 2023 10:00:19 +0000

A new postgraduate programme will train researchers to understand life's origins, search for habitable planets and consider the most profound question of all: are we alone?

No signs (yet) of life on Venus

sc604 — Tue, 14 Jun 2022 15:00:00 +0000

Researchers from the ̽��ֱ�� of Cambridge used a combination of biochemistry and atmospheric chemistry to test the ‘life in the clouds’ hypothesis, which astronomers have speculated about for decades, and found that life cannot explain the composition of the Venusian atmosphere.

Any life form in sufficient abundance is expected to leave chemical fingerprints on a planet’s atmosphere as it consumes food and expels waste. However, the Cambridge researchers found no evidence of these fingerprints on Venus.

Even if Venus is devoid of life, the researchers say their results, reported in the journal Nature Communications, could be useful for studying the atmospheres of similar planets throughout the galaxy, and the eventual detection of life outside our Solar System.

“We’ve spent the past two years trying to explain the weird sulphur chemistry we see in the clouds of Venus,” said co-author Dr Paul Rimmer from Cambridge’s Department of Earth Sciences. “Life is pretty good at weird chemistry, so we’ve been studying whether there’s a way to make life a potential explanation for what we see.”

̽��ֱ��researchers used a combination of atmospheric and biochemical models to study the chemical reactions that are expected to occur, given the known sources of chemical energy in Venus’s atmosphere.

“We looked at the sulphur-based ‘food’ available in the Venusian atmosphere – it’s not anything you or I would want to eat, but it is the main available energy source,” said Sean Jordan from Cambridge’s Institute of Astronomy, the paper’s first author. “If that food is being consumed by life, we should see evidence of that through specific chemicals being lost and gained in the atmosphere.”

̽��ֱ��models looked at a particular feature of the Venusian atmosphere – the abundance of sulphur dioxide (SO2). On Earth, most SO2 in the atmosphere comes from volcanic emissions. On Venus, there are high levels of SO2 lower in the clouds, but it somehow gets ‘sucked out’ of the atmosphere at higher altitudes.

“If life is present, it must be affecting the atmospheric chemistry,” said co-author Dr Oliver Shorttle from Cambridge’s Department of Earth Sciences and Institute of Astronomy. “Could life be the reason that SO2 levels on Venus get reduced so much?”

̽��ֱ��models, developed by Jordan, include a list of metabolic reactions that the life forms would carry out in order to get their ‘food’, and the waste by-products. ̽��ֱ��researchers ran the model to see if the reduction in SO2 levels could be explained by these metabolic reactions.

They found that the metabolic reactions can result in a drop in SO2 levels, but only by producing other molecules in very large amounts that aren’t seen. ̽��ֱ��results set a hard limit on how much life could exist on Venus without blowing apart our understanding of how chemical reactions work in planetary atmospheres.

“If life was responsible for the SO2 levels we see on Venus, it would also break everything we know about Venus’s atmospheric chemistry,” said Jordan. “We wanted life to be a potential explanation, but when we ran the models, it isn’t a viable solution. But if life isn’t responsible for what we see on Venus, it’s still a problem to be solved – there’s lots of strange chemistry to follow up on.”

Although there’s no evidence of sulphur-eating life hiding in the clouds of Venus, the researchers say their method of analysing atmospheric signatures will be valuable when JWST, the successor to the Hubble Telescope, begins returning images of other planetary systems later this year. Some of the sulphur molecules in the current study are easy to see with JWST, so learning more about the chemical behaviour of our next-door neighbour could help scientists figure out similar planets across the galaxy.

“To understand why some planets are alive, we need to understand why other planets are dead,” said Shorttle. “If life somehow managed to sneak into the Venusian clouds, it would totally change how we search for chemical signs of life on other planets.”

“Even if ‘our’ Venus is dead, it’s possible that Venus-like planets in other systems could host life,” said Rimmer, who is also affiliated with Cambridge’s Cavendish Laboratory. “We can take what we’ve learned here and apply it to exoplanetary systems – this is just the beginning.”

̽��ֱ��research was funded by the Simons Foundation and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Sean Jordan, Oliver Shorttle and Paul B Rimmer. ‘Proposed energy-metabolisms cannot explain the atmospheric chemistry of Venus.’ Nature Communications (2022). DOI: 10.1038/s41467-022-30804-8

̽��ֱ��unusual behaviour of sulphur in Venus’ atmosphere cannot be explained by an ‘aerial’ form of extra-terrestrial life, according to a new study.

Even if ‘our’ Venus is dead, it’s possible that Venus-like planets in other systems could host life

Paul Rimmer

NASA/JPL-Caltech

Venus from Mariner 10

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Could acid-neutralising life-forms make habitable pockets in Venus’ clouds?

sc604 — Mon, 20 Dec 2021 20:00:00 +0000

It’s hard to imagine a more inhospitable world than our closest planetary neighbour. With an atmosphere thick with carbon dioxide, and a surface hot enough to melt lead, Venus is a scorched and suffocating wasteland where life as we know it could not survive. ̽��ֱ��planet’s clouds are similarly hostile, blanketing the planet in droplets of sulphuric acid caustic enough to burn a hole through human skin.

And yet, a new study, published in the Proceedings of the National Academy of Sciences, supports the long-held theory that, if life exists, it might make a home in Venus’ clouds. ̽��ֱ��study’s authors, from MIT, Cardiff ̽��ֱ��, and the ̽��ֱ�� of Cambridge, have identified a chemical pathway by which life could neutralise Venus’ acidic environment, creating a self-sustaining, habitable pocket in the clouds.

Within Venus’ atmosphere, scientists have long observed puzzling anomalies — chemical signatures that are hard to explain, such as small concentrations of oxygen and nonspherical particles unlike sulphuric acid’s round droplets. Perhaps most puzzling is the presence of ammonia, a gas that was tentatively detected in the 1970s, and that by all accounts should not be produced through any chemical process known on Venus.

In their new study, the researchers modelled a set of chemical processes to show that if ammonia is indeed present, the gas would set off a cascade of chemical reactions that not only neutralises surrounding droplets of sulphuric acid, but also would explain most of the anomalies observed in Venus’ clouds. As for the source of ammonia itself, the authors propose the most plausible explanation is of biological origin, rather than an non-biological source such as lightning or volcanic eruptions.

̽��ֱ��chemistry suggests that life could be making its own environment on Venus.

This hypothesis is testable, and the researchers provide a list of chemical signatures for future missions to measure in Venus’ clouds, to either confirm or contradict their idea.

“No life that we know of could survive in the Venus droplets,” said study co-author Sara Seager, from MIT. “But the point is, maybe some life is there, and is modifying its environment so that it is livable.”

‘Life on Venus’ was a trending phrase last year, when scientists including Seager and her co-authors reported the detection of phosphine in the planet’s clouds. On Earth, phosphine is a gas that is produced mainly through biological interactions. ̽��ֱ��discovery of phosphine on Venus leaves room for the possibility of life. Since then, however, the discovery has been widely contested.

“ ̽��ֱ��phosphine detection ended up becoming incredibly controversial,” said Seager. “But phosphine was like a gateway, and there’s been this resurgence in people studying Venus.”

Inspired to look more closely, co-author Dr Paul Rimmer from Cambridge’s Department of Earth Sciences began combing through data from past missions to Venus. In these data, he identified anomalies, or chemical signatures, in the clouds that had gone unexplained for decades. In addition to the presence of oxygen and nonspherical particles, anomalies included unexpected levels of water vapor and sulphur dioxide.

Rimmer proposed the anomalies might be explained by dust. He argued that minerals, swept up from Venus’ surface and into the clouds, could interact with sulphuric acid to produce some, but not all of the observed anomalies. He showed the chemistry checked out. But the physical requirements were unfeasible: A massive amount of dust would have to loft into the clouds to produce the observed anomalies. “ ̽��ֱ��hypothesis requires either large amounts of water-rich volcanism or transport of a lot of dust rich in hydroxide salts,” he said. “So far, I have been unable to identify a plausible mineralogy for this mechanism.”

̽��ֱ��researchers wondered if the anomalies could be explained by ammonia. In the 1970s, the gas was tentatively detected in the planet’s clouds by the Venera 8 and Pioneer Venus probes. ̽��ֱ��presence of ammonia, or NH3, was an unsolved mystery.

“Ammonia shouldn’t be on Venus,” said Seager. “It has hydrogen attached to it, and there’s very little hydrogen around. Any gas that doesn’t belong in the context of its environment is automatically suspicious for being made by life.”

If the team were to assume that life was the source of ammonia, could this explain the other anomalies in Venus’ clouds? ̽��ֱ��researchers modeled a series of chemical processes in search of an answer.

They found that if life were producing ammonia in the most efficient way possible, the associated chemical reactions would naturally yield oxygen. Once present in the clouds, ammonia would dissolve in droplets of sulphuric acid, effectively neutralising the acid to make the droplets relatively habitable. ̽��ֱ��introduction of ammonia into the droplets would transform their formerly round, liquid shape into more of a nonspherical, salt-like slurry. Once ammonia dissolved in sulphuric acid, the reaction would trigger any surrounding sulphur dioxide to dissolve as well.

̽��ֱ��presence of ammonia could explain most of the major anomalies seen in Venus’ clouds. ̽��ֱ��researchers also show that sources such as lightning, volcanic eruptions, and even a meteorite strike could not chemically produce the amount of ammonia required to explain the anomalies. Life, however, might.

In fact, the team notes that there are life-forms on Earth — particuarly in our own stomachs — that produce ammonia to neutralise and make livable an otherwise highly acidic environment.

“This hypothesis predicts that the tentative detection of oxygen and ammonia in Venus’s clouds by probes will be confirmed by future missions, and that both life and ammonium sulphite and sulphate are present in the largest droplets in the lower part of the cloud,” said Rimmer, who is also affiliated with the Cavendish Laboratory and the MRC Laboratory for Molecular Biology. “There are also several remaining mysteries: if life is there, how does it propagate in an environment as dry as the clouds of Venus? If it is making water when neutralising the droplets, what happens to that water? If life is not in the clouds of Venus, what alternative abiotic chemistry is taking place to explain this depletion of sulphur dioxide and water? Future lab experiments and missions will be able to test these predictions and may shed light on these outstanding mysteries.”

Scientists may have a chance to check for the presence of ammonia, and signs of life, in the next several years with the Venus Life Finder Missions, a set of proposed privately funded missions that plan to send spacecraft to Venus to measure its clouds for ammonia and other signatures of life.

This research was supported in part by the Simons Foundation, the Change Happens Foundation, and the Breakthrough Initiatives.

Reference:
William Bains et al. ‘Production of ammonia makes Venusian clouds habitable and explains observed cloud-level chemical anomalies.’ Proceedings of the National Academy of Sciences (2021). DOI: 10.1073/pnas.2110889118

Adapted from an MIT news story.

A new study shows it’s theoretically possible. ̽��ֱ��hypothesis could be tested soon with proposed Venus-bound missions.

If life is there, how does it propagate in an environment as dry as the clouds of Venus?

Paul Rimmer

NASA/JPL-Caltech

Venus from Mariner 10

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Hubble sees new atmosphere forming on a rocky exoplanet

sc604 — Thu, 11 Mar 2021 14:00:00 +0000

̽��ֱ��planet GJ 1132 b appears to have begun life as a gaseous world with a thick blanket of atmosphere. Starting out at several times the radius of Earth, this ‘sub-Neptune’ quickly lost its primordial hydrogen and helium atmosphere, which was stripped away by the intense radiation from its hot, young star. In a short period of time, it was reduced to a bare core about the size of Earth.

To the surprise of astronomers, new observations from Hubble have uncovered a secondary atmosphere that has replaced the planet’s first atmosphere. It is rich in hydrogen, hydrogen cyanide, methane and ammonia, and also has a hydrocarbon haze. Astronomers theorise that hydrogen from the original atmosphere was absorbed into the planet’s molten magma mantle and is now being slowly released by volcanism to form a new atmosphere. This second atmosphere, which continues to leak away into space, is continually being replenished from the reservoir of hydrogen in the mantle’s magma.

“This second atmosphere comes from the surface and interior of the planet, and so it is a window onto the geology of another world,” said team member Paul Rimmer from the ̽��ֱ�� of Cambridge. “A lot more work needs to be done to properly look through it, but the discovery of this window is of great importance.”

“We first thought that these highly radiated planets would be pretty boring because we believed that they lost their atmospheres,” said team member Raissa Estrela of the Jet Propulsion Laboratory at the California Institute of Technology in Pasadena, California, USA. “But we looked at existing observations of this planet with Hubble and realised that there is an atmosphere there.”

“How many terrestrial planets don’t begin as terrestrials? Some may start as sub-Neptunes, and they become terrestrials through a mechanism whereby light evaporates the primordial atmosphere. This process works early in a planet’s life, when the star is hotter,” said team leader Mark Swain of the Jet Propulsion Laboratory. “Then the star cools down and the planet’s just sitting there. So you’ve got this mechanism that can cook off the atmosphere in the first 100 million years, and then things settle down. And if you can regenerate the atmosphere, maybe you can keep it.”

In some ways, GJ 1132 b has various parallels to Earth, but in some ways, it is also very different. Both have similar densities, similar sizes, and similar ages, being about 4.5 billion years old. Both started with a hydrogen-dominated atmosphere, and both were hot before they cooled down. ̽��ֱ��team’s work even suggests that GJ 1132 b and Earth have similar atmospheric pressure at the surface.

However, the planets’ formation histories are profoundly different. Earth is not believed to be the surviving core of a sub-Neptune. And Earth orbits at a comfortable distance from our yellow dwarf Sun. GJ 1132 b is so close to its host red dwarf star that it completes an orbit the star once every day and a half. This extremely close proximity keeps GJ 1132 b tidally locked, showing the same face to its star at all times — just as our moon keeps one hemisphere permanently facing Earth.

“ ̽��ֱ��question is, what is keeping the mantle hot enough to remain liquid and power volcanism?” asked Swain. “This system is special because it has the opportunity for quite a lot of tidal heating.”

̽��ֱ��phenomenon of tidal heating occurs through friction, when energy from a planet’s orbit and rotation is dispersed as heat inside the planet. GJ 1132 b is in an elliptical orbit, and the tidal forces acting on it are strongest when it is closest to or farthest from its host star. At least one other planet in the host star’s system also exerts a gravitational pull on the planet. ̽��ֱ��consequences are that the planet is squeezed or stretched by this gravitational “pumping.” That tidal heating keeps the mantle liquid for a long time. A nearby example in our own Solar System is the Jovian moon, Io, which has continuous volcanism as a result of a tidal tug-of-war between Jupiter and the neighbouring Jovian moons.

̽��ֱ��team believes the crust of GJ 1132 b is extremely thin, perhaps only hundreds of feet thick. That’s much too feeble to support anything resembling volcanic mountains. Its flat terrain may also be cracked like an eggshell by tidal flexing. Hydrogen and other gases could be released through such cracks.

“This atmosphere, if it’s thin — meaning if it has a surface pressure similar to Earth — probably means you can see right down to the ground at infrared wavelengths. That means that if astronomers use the James Webb Space Telescope to observe this planet, there’s a possibility that they will see not the spectrum of the atmosphere, but rather the spectrum of the surface,” said Swain. “And if there are magma pools or volcanism going on, those areas will be hotter. That will generate more emission, and so they’ll potentially be looking at the actual geological activity — which is exciting!”

This result is significant because it gives exoplanet scientists a way to figure out something about a planet's geology from its atmosphere,” said Rimmer, who is affiliated both with Cambridge’s Cavendish Laboratory and Department of Earth Sciences. “It is also important for understanding where the rocky planets in our own Solar System — Mercury, Venus, Earth and Mars, fit into the bigger picture of comparative planetology, in terms of the availability of hydrogen versus oxygen in the atmosphere.”

Adapted from an ESA/JPL press release.

For the first time, scientists using the NASA/ESA Hubble Space Telescope have found evidence of volcanic activity reforming the atmosphere on a rocky planet around a distant star. ̽��ֱ��planet, GJ 1132 b, has a similar density, size, and age to Earth.

It is a window onto the geology of another world

Paul Rimmer

NASA, ESA, and R. Hurt (IPAC/Caltech)

Artist’s impression of the exoplanet GJ 1132 b

Yes

Hints of life discovered on Venus

sc604 — Mon, 14 Sep 2020 15:00:00 +0000

Astronomers have speculated for decades that high clouds on Venus could offer a home for microbes – floating free of the scorching surface, but tolerating very high acidity. ̽��ֱ��detection of phosphine molecules, which consist of hydrogen and phosphorus, is an important step in the search for life beyond Earth, a key question in science. ̽��ֱ��results are reported in the journal Nature Astronomy.

̽��ֱ��discovery was made by Professor Jane Greaves while she was a visitor at the ̽��ֱ�� of Cambridge’s Institute of Astronomy. Greaves and her collaborators used the James Clerk Maxwell Telescope (JCMT) in Hawaii to detect the phosphine, and followed up their discovery on the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. Both facilities observe Venus at a wavelength of about 1 millimetre, much longer than the human eye can see.

“This was an experiment made out of pure curiosity, really – taking advantage of JCMT’s powerful technology, and thinking about future instruments,” said Greaves, who is based at Cardiff ̽��ֱ��. “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!”

Luckily, conditions were good at ALMA for follow-up observations while Venus was at a suitable angle to Earth. Processing the data was challenging, however, as ALMA isn’t usually looking for subtle effects in bright objects like Venus.

“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,” said Greaves.

Using existing models of the Venusian atmosphere to interpret the data, the researchers found that phosphine is present but scarce – only about twenty molecules in every billion. ̽��ֱ��astronomers then ran calculations to see if the phosphine could come from natural processes on Venus. They caution that some information is lacking – in fact, the only other study of phosphorus on Venus came from one lander experiment, carried by the Soviet Vega 2 mission in 1985.

On Earth, phosphine is only made industrially or by microbes that thrive in oxygen-free environments. Co-author Dr William Bains from MIT led the work on assessing natural ways to make phosphine on Venus. Ideas included sunlight, minerals blown upwards from the surface, volcanoes, or lightning, but none of these could make anywhere near enough. Natural 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 on Venus, terrestrial organisms would only need to work at about 10% of their maximum productivity, according to calculations by co-author Dr Paul Rimmer of Cambridge’s Department of Earth Sciences. Any microbes on Venus will likely be very different from their Earth cousins though, to survive in hyper-acidic conditions.

“This discovery brings us right to the shores of the unknown,” said Rimmer, who is also affiliated with Cambridge's Cavendish Laboratory. “Phosphine is very hard to make in the oxygen-rich, hydrogen-poor clouds of Venus and fairly easy to destroy. ̽��ֱ��presence of life is the only known explanation for the amount of phosphine inferred by observations.

“Both of these facts lie at the edge of our knowledge: the observations could be caused by an unknown molecule, or could be caused by chemistry we’re not aware of. Ultimately, the only way to find out what's really happening is to send a mission into the clouds of Venus to take a sample of the droplets and look at them to see what's inside.”

Earth bacteria can absorb phosphate minerals, add hydrogen, and ultimately expel phosphine gas. It costs them energy to do this, so why they do it is not clear. ̽��ֱ��phosphine could be just a waste product, but other scientists have suggested purposes like warding off rival bacteria.

Co-author Dr Clara Sousa Silva from MIT was also thinking about searching for phosphine as a ‘biosignature’ gas of non-oxygen-using life on planets around other stars because normal chemistry makes so little of it. “Finding phosphine on Venus was an unexpected bonus,” she said. “ ̽��ֱ��discovery raises many questions, such as how any organisms could survive. On Earth, some microbes can cope with up to about 5% acid in their environment – but the clouds of Venus are almost entirely made of acid.”

Other possible biosignatures in the Solar System may exist, like methane on Mars and water venting from the icy moons Europa and Enceladus. On Venus, it has been suggested that dark streaks where ultraviolet light is absorbed could come from colonies of microbes. ̽��ֱ��Akatsuki spacecraft, launched by the Japanese space agency JAXA, is currently mapping these dark streaks to understand more about this unknown ultraviolet absorber.

̽��ֱ��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 microbes to survive there. ̽��ֱ��researchers are investigating the possibility that the microbes could shield themselves inside droplets.

̽��ֱ��team is now awaiting more telescope time to establish whether the phosphine is in a relatively temperate part of the clouds and to look for other gases associated with life. New space missions could also travel to our neighbouring planet, and sample the clouds to search for signs of life.

Professor Emma Bunce, President of the Royal Astronomical Society, said: “A key question in science is whether life exists beyond Earth, and the discovery by Professor Jane Greaves and her team is a key step forward in that quest. I’m particularly delighted to see UK scientists leading such an important breakthrough – something that makes a strong case for a return space mission to Venus.”

Reference:
Jane S. Greaves et al. ‘Phosphine Gas in the Cloud Decks of Venus.’ Nature Astronomy (2020). DOI: 10.1038/s41550-020-1174-4

Adapted from an RAS press release.

A UK-led team of astronomers has discovered a rare molecule – phosphine – in the clouds of Venus, pointing to the possibility of extra-terrestrial ‘aerial’ life.

̽��ֱ��presence of life is the only known explanation for the amount of phosphine inferred by observations

Paul Rimmer

JAXA / ISAS / Akatsuki Project Team

Synthesized false colour image of Venus

Yes

Scientists identify exoplanets where life could develop as it did on Earth

sc604 — Wed, 01 Aug 2018 18:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge and the Medical Research Council Laboratory of Molecular Biology (MRC LMB), found that the chances for life to develop on the surface of a rocky planet like Earth are connected to the type and strength of light given off by its host star.

Their study, published in the journal Science Advances, proposes that stars which give off sufficient ultraviolet (UV) light could kick-start life on their orbiting planets in the same way it likely developed on Earth, where the UV light powers a series of chemical reactions that produce the building blocks of life.

̽��ֱ��researchers have identified a range of planets where the UV light from their host star is sufficient to allow these chemical reactions to take place, and that lie within the habitable range where liquid water can exist on the planet’s surface.

“This work allows us to narrow down the best places to search for life,” said Dr Paul Rimmer, a postdoctoral researcher with a joint affiliation at Cambridge’s Cavendish Laboratory and the MRC LMB, and the paper’s first author. “It brings us just a little bit closer to addressing the question of whether we are alone in the universe.”

̽��ֱ��new paper is the result of an ongoing collaboration between the Cavendish Laboratory and the MRC LMB, bringing together organic chemistry and exoplanet research. It builds on the work of Professor John Sutherland, a co-author on the current paper, who studies the chemical origin of life on Earth.

In a paper published in 2015, Professor Sutherland’s group at the MRC LMB proposed that cyanide, although a deadly poison, was in fact a key ingredient in the primordial soup from which all life on Earth originated.

In this hypothesis, carbon from meteorites that slammed into the young Earth interacted with nitrogen in the atmosphere to form hydrogen cyanide. ̽��ֱ��hydrogen cyanide rained to the surface, where it interacted with other elements in various ways, powered by the UV light from the sun. ̽��ֱ��chemicals produced from these interactions generated the building blocks of RNA, the close relative of DNA which most biologists believe was the first molecule of life to carry information.

In the laboratory, Sutherland’s group recreated these chemical reactions under UV lamps, and generated the precursors to lipids, amino acids and nucleotides, all of which are essential components of living cells.

“I came across these earlier experiments, and as an astronomer, my first question is always what kind of light are you using, which as chemists they hadn’t really thought about,” said Rimmer. “I started out measuring the number of photons emitted by their lamps, and then realised that comparing this light to the light of different stars was a straightforward next step.”

̽��ֱ��two groups performed a series of laboratory experiments to measure how quickly the building blocks of life can be formed from hydrogen cyanide and hydrogen sulphite ions in water when exposed to UV light. They then performed the same experiment in the absence of light.

“There is chemistry that happens in the dark: it’s slower than the chemistry that happens in the light, but it’s there,” said senior author Professor Didier Queloz, also from the Cavendish Laboratory. “We wanted to see how much light it would take for the light chemistry to win out over the dark chemistry.”

̽��ֱ��same experiment run in the dark with the hydrogen cyanide and the hydrogen sulphite resulted in an inert compound which could not be used to form the building blocks of life, while the experiment performed under the lights did result in the necessary building blocks.

̽��ֱ��researchers then compared the light chemistry to the dark chemistry against the UV light of different stars. They plotted the amount of UV light available to planets in orbit around these stars to determine where the chemistry could be activated.

They found that stars around the same temperature as our sun emitted enough light for the building blocks of life to have formed on the surfaces of their planets. Cool stars, on the other hand, do not produce enough light for these building blocks to be formed, except if they have frequent powerful solar flares to jolt the chemistry forward step by step. Planets that both receive enough light to activate the chemistry and could have liquid water on their surfaces reside in what the researchers have called the abiogenesis zone.

Among the known exoplanets which reside in the abiogenesis zone are several planets detected by the Kepler telescope, including Kepler 452b, a planet that has been nicknamed Earth’s ‘cousin’, although it is too far away to probe with current technology. Next-generation telescopes, such as NASA’s TESS and James Webb Telescopes, will hopefully be able to identify and potentially characterise many more planets that lie within the abiogenesis zone.

Of course, it is also possible that if there is life on other planets, that it has or will develop in a totally different way than it did on Earth.

“I’m not sure how contingent life is, but given that we only have one example so far, it makes sense to look for places that are most like us,” said Rimmer. “There’s an important distinction between what is necessary and what is sufficient. ̽��ֱ��building blocks are necessary, but they may not be sufficient: it’s possible you could mix them for billions of years and nothing happens. But you want to at least look at the places where the necessary things exist.”

According to recent estimates, there are as many as 700 million trillion terrestrial planets in the observable universe. “Getting some idea of what fraction have been, or might be, primed for life fascinates me,” said Sutherland. “Of course, being primed for life is not everything and we still don’t know how likely the origin of life is, even given favourable circumstances - if it’s really unlikely then we might be alone, but if not, we may have company.”

̽��ֱ��research was funded by the Kavli Foundation and the Simons Foundation.

Reference:
Paul B. Rimmer et al. ‘ ̽��ֱ��Origin of RNA Precursors on Exoplanets.’ Science Advances (2018). DOI: 10.1126/sciadv.aar3302

Inset image: Diagram of confirmed exoplanets within the liquid water habitable zone (as well as Earth). Credit: Paul Rimmer

Scientists have identified a group of planets outside our solar system where the same chemical conditions that may have led to life on Earth exist.

This work brings us just a little bit closer to addressing the question of whether we are alone in the universe.

Paul Rimmer

NASA Ames/JPL-Caltech/T. Pyle

Artist's concept depicting one possible appearance of the planet Kepler-452b

Yes