Since the discovery of a chemical called phosphine on Venus in September last year, the scientific community has been in a vicious cycle. Scientists have published papers back and forth, trying to dismantle or support the claim.
With two new papers landing this week, some say the nails are hammered into the phosphine coffin. We suspect, however, that the detection will continue to be examined and discussed for some time.
So what’s the real deal? Read on for a short manual.
Phosphine on Venus? Why does it matter?
The discovery itself is quite fascinating. Using two different instruments at different times – the James Clerk Maxwell Telescope (JCMT) in 2017 and the Atacama Large Millimeter / Submillimeter Array (ALMA) in 2019 – a team led by astrobiologist Jane Greaves of Cardiff University in the UK detected the spectral signature of a substance chemical called phosphine in the Venusian atmosphere, at 20 parts per billion. The findings were published in Nature Astronomy.
As we reported at the time, here on Earth, phosphine was found in abundance in anaerobic (low oxygen) ecosystems. It is found in swamps and muds, where anaerobic microbes thrive. It is found in the intestines and, well, in farts. Somehow, anaerobic microorganisms produce phosphine. And the clouds of Venus are anaerobic.
Although Greaves and her team ruled out many possible ways to form abiotic Venus phosphine, they were very careful to note that there may be other ways in which the chemical could occur. First, here on Earth volcanoes produce phosphine, and we have evidence that Venus is still volcanically active. (A volcanic origin was later found plausible in another prepress.)
In any case, the detection was fascinating, but the mention of a microbial origin led to a lot of speculation and a lot of subsequent examinations by other scientists.
What happened next?
Well, everything got a little complicated. First, a team of scientists analyzed historical data from Venus and found that the Pioneer spacecraft could have detected phosphine by 1978. That work has not yet been accepted for publication. Another sent to the diary Science and also has not yet been evaluated by colleagues, he claimed to have detected the amino acid glycine – a block of protein – on Venus.
Other scientists have begun to look at the data. Three separate papers – one published by Astronomy and astrophysics on ALMA data, another published in Monthly notifications from the Royal Astronomical Society on JCMT data and the other reanalyzing both data sets and still awaiting peer review – found no significant detection of phosphine in the atmosphere of Venus.
Then it turned out that there was an error in processing the data from ALMA’s observations. Greaves requested that the data be reprocessed; these reprocessed data were made available to the public in November 2020.
Greaves and her team analyzed the new data and found that they could still detect phosphine on Venus, but in smaller amounts – an overall average of 1 to 4 parts per billion, with localized peaks of 5 to 10 parts per billion.
Because sulfur dioxide and phosphine absorb both radiation near the 266.94 GHz frequency, some have suggested that Greaves and her team may have detected sulfur dioxide (also produced by volcanic activity) and not phosphine. In their new paper, Greaves et al. excluded sulfur dioxide. The spectral absorption line interpreted as the chemical footprint of phosphine, they said, was too wide to be sulfur dioxide and was not enough on Venus to produce the observed signal.
A third paper from Greaves and her team followed, defending the robustness of the phosphine signal.
OK, so why did he get back to the news now?
Two new papers fell, one of which was published in The Astrophysical Journal Letters, and the other of which was accepted for publication in The Astrophysical Journal Letters, data reanalysis. Both papers help mount the pile against phosphine.
The first paper reanalyzed both ALMA datasets, before and after they were reprocessed. The team found a spectral line at 266.94 GHz in the previous data set, but did not signal significantly after reprocessing. They also found that sulfur dioxide can occur in at least 10 parts per billion and cannot be detected by ALMA, suggesting that it may be more abundant than Greaves and her team thought.
The second paper used data from decades of observations of Venus to model conditions in the Venusian atmosphere and to determine how phosphine and sulfur dioxide would behave. They found that the 266.94 GHz signal best matches an origin at about 80 kilometers (50 miles) above the cloud decks, rather than between 50 and 60 kilometers, as proposed by Greaves and her team.
At this altitude, phosphine would not last long, so the best explanation would be sulfur dioxide, they concluded.
Is this the end? Is Venus Phosphine Detection Dead?
Not even close! For starters, Greaves and her team are likely to respond to new work, which will trigger more responses, with more simulations and modeling and number reduction, and perhaps even experimentation to determine what the possibilities and probabilities are.
In addition, nothing we have seen so far is conclusive. It is more than likely that the only way we can put the rest to rest is by taking more detailed observations with more powerful tools. We might wait a while for this. There are several proposed missions to Venus in progress, but there is often a long time between proposal and execution.
However, this is science to the fullest. There is a “true” and a “false” here. Either there is phosphine on Venus, or it doesn’t exist. Scientists will use their creativity to try to solve the problem, which will lead to refined techniques and analysis tools.
Finally, we will find out the truth. And whatever that truth is, it will teach us something new about our Universe.