EarthSky messed up by publishing an article that was meant for tomorrow, the 14th, and luckily, someone archived it before they hit the delete button. Nature will publish a paper tomorrow where MIT researchers discuss the detection of phosphine gas in Venus' atmosphere. Phosphine is considered a biomarker, meaning that its presence likely indicates the presence of certain forms of life that produce it, as researchers couldn't find any way it could form without human or biological action. Here's the archive of the article: (the links within aren't working for obvious reasons)
https://archive.is/L7MT1
https://archive.is/L7MT1
Most of us are familiar with the old quote from Arthur Conan Doyle, “Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.” Those words may be more apropos than ever this week, as scientists announced an incredible discovery: tentative evidence for microbial life on Venus! As we know, Venus is a scorching and inhospitable world on the surface, probably the last place you’d expect to find any kind of life. But the hints of these tiny Venusians comes not from the planet’s surface, but rather from higher up in its atmosphere, where conditions can be remarkably Earth-like.
The exciting findings come from scientists in the US and UK, at the Massachusetts Institute of Technology (MIT), Cardiff University, University of Manchester and others. Jane Greaves of Cardiff University lead the study.
The new peer-reviewed research paper was published in Nature Astronomy today, September 14, 2020. The Royal Astronomical Society also provided an online press briefing for journalists via Zoom, with three of the researchers to discuss the results, as well as issuing its own news release.
It should be noted that this is not quite yet proof of life on Venus, but the researchers make a compelling case.
For as long as we’ve known about conditions on the planet thanks to visiting space probes, Venus has always been considered one of the least likely to support life of any kind. With scorching temperatures hot enough to melt lead and crushing air pressure at the surface, along with large amounts of sulfuric acid in its clouds, Venus is far from being a welcoming place.
Some scientists, however, have speculated that life might be possible higher up in the atmosphere, where temperatures and pressures are Earth-like in a “temperate zone.” It is in this zone that the discovery was made.
What did the researchers find?
Simply put, a gas that shouldn’t be there, and on Earth is considered a conclusive biosignature: phosphine, a very stinky gas. As far as scientists know, there are only two ways to produce it, either artificially in a lab, or by certain kinds of microbes that live in oxygen-free environments. Since it is rather unlikely there any alien labs on Venus, that leaves microbes.
The researchers made the detection using the James Clerk Maxwell Telescope (JCMT) in Hawaii, and the Atacama Large Millimeter Array (ALMA) observatory in Chile.
Researchers from MIT had previously published studies showing that if phosphine was to ever be found on another rocky planet, it would be a sure sign of life there. Hence why this discovery is so provocative. But before announcing this tantalizing evidence, the researchers, of course, wanted to try to rule out other explanations. They considered and tested many various scenarios where this gas might be produced without life, but as they acknowledge, they came up empty. Clara Sousa-Silva at MIT, whose career specialty is studying phosphine, said in a statement:
It’s very hard to prove a negative. Now, astronomers will think of all the ways to justify phosphine without life, and I welcome that. Please do, because we are at the end of our possibilities to show abiotic processes that can make phosphine.
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.
Co-author Janusz Petkowski added:
That’s a pretty definitive statement to make.This means either this is life, or it’s some sort of physical or chemical process that we do not expect to happen on rocky planets.
We really went through all possible pathways that could produce phosphine on a rocky planet. If this is not life, then our understanding of rocky planets is severely lacking.
Greaves said:
The researchers processed the data for six months before becoming convinced the phosphine was really there. According to Anita Richards, of the UK ALMA Regional Centre and The University of Manchester: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!
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.
William Bains
at MIT, who led the work on trying to assess other natural ways to make phosphine on Venus. 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 kinds of sources could only make, at most, one ten thousandth of the amount of phosphine that the telescopes saw. So something is producing a lot more of the gas. According to Paul Rimmer at Cambridge University, terrestrial organisms would only need to work at about 10% of their maximum productivity in order to produce the amount of phosphine found on Venus.
On Earth, phosphine is produced by microbes that don’t need oxygen. They absorb phosphate minerals, add hydrogen, and ultimately expel phosphine gas. Since Venus has virtually no oxygen in its atmosphere, that’s another similarity suggesting the gas actually is coming from microbes.
Since Venus is much too hot at its surface for any known earthly microbes, they must be in its atmosphere. There is a temperate region, between 48 and 60 kilometers above the surface, where temperatures range from 30 to 200 degrees Fahrenheit. That’s the habitable zone on Venus, and just happens to be where the phosphine was found. As Petkowski noted:
