Media releaseFrom: Springer Nature
Nature Media Release: Phosphine detected in the clouds of Venus
Phosphine gas has been detected in the atmosphere of Venus, according to a paper published in Nature Astronomy. This finding suggests that Venus could host unknown photochemical or geochemical processes.
On Earth, phosphine is a gas that is produced predominantly by anaerobic biological sources. The conditions at the surface of Venus are hostile to life, but the environment of its upper cloud deck — around 53–62 km above the surface — is temperate. However, the make-up of the clouds is highly acidic, and in such conditions phosphine would be destroyed very quickly.
Jane Greaves and colleagues observed Venus with the James Clerk Maxwell Telescope and the Atacama Large Millimeter/submillimeter Array in 2017 and 2019, respectively. They detected a spectral signature that is unique to phosphine, and estimated an abundance of 20 parts-per-billion of phosphine in Venus’s clouds. The authors investigated different ways the phosphine may have been produced, including from sources on the surface of the planet, micrometeorites, lightning, or chemical processes happening within the clouds. Ultimately, they were unable to determine the source of the trace quantities of phosphine.
The authors argue that the detection of phosphine is not robust evidence for microbial life and only indicates potentially unknown geological or chemical processes occurring on Venus. Further observations and modelling are needed to explore the origin of phosphine in Venus’s atmosphere.
James Clerk Maxwell Telescope Media Release: JCMT finds hints of life on Venus
MAUNAKEA HAWAI`I - An international team of astronomers, led by Professor Jane Greaves of Cardiff University, UK, 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. 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!”, said Jane, who first spotted signs of phosphine in observations from the James Clerk Maxwell Telescope (JCMT) in Hawai`i.
Astronomers have speculated for decades that high clouds on Venus could offer a home for microbes – floating free of the scorching surface, with access to water and sunlight, but needing to tolerate very high acidity. The detection of phosphine, which consists of hydrogen and phosphorus, could point to this extra-terrestrial ‘aerial’ life. The new discovery is described in a paper published today in Nature Astronomy.
The first detection of phosphine in the clouds of Venus was made using the JCMT in Hawai`i. The team were then awarded time to follow up their discovery with 45 telescopes of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. 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. “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 Jane.
The astronomers then ran calculations to see if the phosphine could come from natural processes on Venus. Massachusetts Institute of Technology scientist Dr William Bains led the work on assessing natural ways to make phosphine. Some ideas included sunlight, minerals blown upwards from the surface, volcanoes, or lightning, but none of these could make anywhere near enough of it. Natural sources were found to make at most one ten thousandth of the amount of phosphine that the telescopes saw. In contrast the team found that in order to create the observed quantity of phosphine on Venus, terrestrial organisms would only need to work at about 10% of their maximum productivity. Any microbes on Venus will though likely be very different to their Earth cousins. Earth bacteria can absorb phosphate minerals, add hydrogen extracted from water, and ultimately expel phosphine gas.
Before the new study, team member and MIT researcher, Dr Clara Sousa Silva, had thought 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. 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 this 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 centigrade, they are incredibly acidic – around 90% sulphuric acid – posing major issues for microbes to survive there. Prof Sara Seager and Dr Janusz Petkowski, both at MIT, are investigating how microbes could shield themselves inside scarce water droplets.
The team are now eagerly 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. This result also has implications in the search for life outside our Solar system.
On hearing the results of the JCMT study, the JCMT’s Deputy Director Dr Jessica Dempsey said “These results are incredible” and went on to say “this discovery made in Hawai`i, by the JCMT, was made with a single pixel instrument. This is the very same instrument that also captured the first image of a Black Hole, Pōwehi. The discovery of phosphine in the atmosphere of Venus really showcases the breadth of cutting-edge research undertaken by astronomers using the JCMT. I am so pleased of the efforts from all our staff here in Hawai`i”
Former UH Hilo astronomy student, E’Lisa Lee who took some of the JCMT data during her time working as a part-time JCMT telescope operator summed up her feelings “An observed biochemical process occurring on anything other than Earth has the greatest and most profound implications for our understanding of life on Earth, and life as a concept.” Adding “Being able to participate in the scientific process, as an operator at JCMT was an incredible and humbling experience. It is my sincerest hope that further observations will allow for greater exploration of Venusian clouds and everything beyond.” E’lisa currently studying for her Master’s degree in physics at Fresno State University.
The JCMT instrument that captured this phosphine discovery has since retired and been replaced by a new and more sensitive instrument known as Nāmakanui. On the potential of this new instrument, Jessica commented “Like it’s namesake, the big-eyed fish hunting food in the dark waters, we will turn the far more sensitive Nāmakanui back to Venus in this hunt for life in our universe. This is just the beginning, and I’ve never been more excited to be a part of our boundary-pushing JCMT team.”