On September 14, the media echoed a shocking finding: the ALMA telescope in Chile (the most powerful we have) had detected a biomarker, that is, a molecule whose presence is related to the existence of microbial life. It was about phosphane or phosphine (PH3) that, on Earth, is excreted by microorganisms in oxygen-free environments.
The detection quickly amazed the general public. But scientific discoveries, especially those of this caliber, require a long time and, above all, multiple and unequivocal checks to establish their robustness. At that time, the ALMA project astronomer Sergio Martín, interviewed by VERY INTERESTING, warned that the detection had occurred “at the limit of the capacity of our most powerful telescope” and called us to be cautious, since it could still have occurred “Some technological error in the detection”.
As well; On October 26, a scientific study with a very clear and direct headline ( No phosphine in the atmosphere of Venus or ‘There is no phosphine in the atmosphere of Venus’) was released on the pre-publication platform Arxiv.org. For scientific communicators, articles in the prepublication or preprint phase require careful treatment: it means that they have not yet completed all the requirements to be considered suitable for publication by a scientific journal. That is, they must be peer-reviewed (professionals equivalent to those who sign the study) and this peer-review must be ‘double blind’ (anonymously, with no professional or personal interests involved in one direction or the other).
Once this is clarified, let’s go on to review what the new study says, signed by Gerónimo Villanueva as the main author among twenty-six other researchers. The report explains how the apparent detection of phosphine, through millimeter wave radio observations (which it calls G2020) “is not compatible with our data analysis.”
The ALMA telescope identified the presence of phosphine on Venus through the analysis of the waves, which we know as spectrography. To understand it better, this detection occurs in a similar way to how a radio searches for a station , until it reaches the desired frequency. Well, for Villanueva’s team, there is a calibration error that led the scientists to mistakenly believe that the ALMA data reflected the presence of phosphane.
For more data, the team also affects the altitude at which the detection occurred. The surface of Venus is about 500 ° C in temperature, but in the high clouds of the atmosphere a more temperate climate is ‘breathed’. The detection of phosphane by the ALMA telescope occurred at about 60 kilometers of altitude, while the new study suggests that the presence of phosphane should have occurred at somewhat higher altitudes : “For any sign of PH3 to be produced in ALMA spectra o JCMT, PH3 must be presented at altitudes above 70 kilometers ”.
“Finally we conclude that this detection of PH3 in the atmosphere of Venus is not supported by our analysis of the data”, can be read in the preprint.
Disappointing, isn’t it?
However, this is not the first study to critique the life-related presence of phosphine on Venus. On October 2, another report, while not challenging the detection, proposed an alternative explanation for its existence: volcanism . “We propose an abiotic [non-living] geological mechanism that would explain the abundance of phosphine detected by Greaves and his colleagues. We estimate that small amounts of phosphides formed in the mantle would be brought to the surface by volcanism and then expelled into the atmosphere, where they could react with water or sulfuric acid to form phosphine. […] We suggest that active volcanism today could produce a rate comparable to that required to produce the phosphide source of phosphine. Our hypothesis requires that Venus is currently experiencing a high rate of basaltic volcanism, which is consistent with spacecraft observations and laboratory experiments, ”you can read in the article, which is also in prepublication phase.
Finally, on October 21, another preprint was titled as follows: ‘ No statistically significant detection of phosphine?’ (‘No statistically significant detection of phosphine?’). In it, the “statistical reliability” of line detection is evaluated by means of a new independent analysis of the ALMA data. The conclusion they reached is the following: “We found that the fit of the 12th order polynomial to the spectral passband used in the published study leads to false results.” And they add: “We consider a characteristic at a statistically unreliable level that can be linked to a probability of false positive .”
Has the presence of phosphane on Venus been disproved?
Now, can we definitively reject the possibility of phosphane on Venus? Should we declare it false? Perhaps it is too early to pronounce . To begin with, because the three studies we have mentioned are still in the prepublication phase. And, on the other hand, as the astronomer Sergio Martín explained to us well during the interview, because all this research, far from discouraging us, should motivate us to continue investigating. In any case, this issue opens the door to continue inquiring about life, not only on Venus, but in other corners of our solar system.
It is possible that we will have to wait for other instruments, probably space probes orbiting the planet, to make new measurements that can ensure the certainty of this detection. And yet, remember that its presence is just that: the phosphine finding is not a direct detection of life; it never was.
Finding life, even if it is microbial, in other corners outside our planet is an exciting mission, which may take us a few decades, which requires patience and a lot of caution. And along the way, we may have to take some promising a priori detections, like this one, with a grain of salt.
Más información y fuentes:
Villanueva G.L, ET AL. “No phosphine in the atmosphere of Venus” PREPRINT “Matters Arising”, Nature, 2020.
Ngoc Truong & Jonathan I. Lunine, “Hypothesis Perspectives: Might active volcanisms today contribute to the presence of phosphine in Venus’s atmosphere?”, PREPRINT, 2020.
I.A.G. Snellen, “Re-analysis of the 267-GHz ALMA observations of Venus”, PREPRINT, Astronomy & Astrophysics, 2020.
