A year after discovering phosphine gas in the atmosphere of Venus, a signal that many believe may be a sign of microscopic life, the research team behind the discovery has re-examined the findings. And, they say, this analysis only confirms their original findings.

On Earth, most living things release carbon dioxide or oxygen into the atmosphere. But some species of organisms that live in extreme conditions, dubbed “extremophiles,” can emit phosphorus gas, known as phosphine.

In 2020, researchers examining data from a pair of large telescopes found distinctive signatures of this gas in the Venusian atmosphere, and in concentrations that indicate the presence of life spewing phosphine.

“The chemical phosphine (PH3) is considered a biomarker because it is difficult to create by the normal chemical processes believed to occur on or around a rocky planet such as Venus,” the NASA report explains.

The discovery sparked a wave of reactions, from outright elation over the discovery of signs of extraterrestrial life to doubts about whether the phosphine signal had been detected at all.

In an attempt to solve this problem, at least as far as possible before in situ measurements by future probes can answer the question once and for all, the research team, which initially got controversial results, took a fresh look at the data. And what they found seems to confirm their original conclusion.

“Re-analysis of inherited data collected by NASA’s Pioneer-Venus Neutral Gas Mass Spectrometer (LNMS) at 51.3 km shows the presence of PH3 in the clouds of Venus,” the researchers explain in a statement.

Moreover, they note that “PH3 (phosphine) is the only P-containing molecule that matches the data and is in gas form at 51.3 km above the level of Venus.

This is quite convincing, the researchers note, because “+P does not overlap with any other fragment of neutral gas mass expected from the atmosphere of Venus, which gives +P a unique and reliable detection.”

Feeling confident in their conclusion, the researchers confirmed the result, including ruling out a possible false signal from a naturally occurring process.

“It could be argued that there are very small amounts, such as phosphoric acid vapor, that could have fragmented into +P,” the researchers suggested, “but confirmatory acid fragmentation ions were not detected, and they should have been.”

In the end, the research team concluded, “We insist on the existence of phosphine in the atmosphere of Venus, while recognizing that the dispute may never be resolved until in situ measurements in the atmosphere of Venus are returned.”

In June 2021, NASA announced a pair of future missions to the fiery world, both of which will feature instruments capable of ending the phosphine controversy once and for all. The two missions, named DAVINCI+ (Exploring Noble Gases, Chemistry and Imaging in Venus’ Deep Atmosphere) and VERITAS (Exploring Venus’ Radiative Capability, Radar, InSAR, Topography and Spectroscopy), are part of NASA’s Discovery program.

“Using the advanced technology that NASA has developed and refined over many years of missions and technology programs, we are beginning a new decade of studying Venus to understand how an Earth-like planet can become a greenhouse,” NASA Assistant Administrator for Science Thomas Zurbuchen said in a statement about the two new missions. “Our goals are profound. It’s not just to understand planetary evolution and habitability in our own solar system, but to go beyond those limits to exoplanets, an exciting and evolving area of NASA research.”

The launch of both DAVINCI+ and VERITAS satellites is expected around the end of this decade, so it may be some time before that question is answered definitively.

However, given the detailed reanalysis of the original signal by a team of researchers, as well as attempts by these same researchers to respond directly to each of the previous criticisms of their original finding, the options seem to be increasingly narrowed toward the original finding being credible.