According to the researchers, it is still possible that the observed phosphine can be explained by biological processes.
In September published phosphine finding The atmosphere of Venus made the world excited about the possible signs of life on our neighboring planet. Now an international team of researchers who have made the discovery has had to soften their claims, scientific journals say Science and Nature.
Re-analysis of the data revealed that the Venus atmosphere contains up to one-seventh of the amount of the initial estimate. Scientists now describe their phosphine discovery only tentatively.
The group reports on the new ones their results on Tuesday at the Arxiv Publishing Service.
Original phosphine discovery was made with two telescopes in 2017 and 2019. Professor at the University of Cardiff Jane Greaves and colleagues estimate that the phosphine content in the cloud layer of the planet would be about 20 billionths.
According to the researchers, such a high concentration in the atmosphere of a rocky planet could be a sign of microbial life. On gas planets, phosphine is formed at high temperatures and pressures in geochemical processes, but on Earth, this gas is only produced in biological processes when organic matter decomposes.
The study collected criticism immediately after its publication. Four independent studies showed methodological shortcomings and the results could not be replicated.
Last month, Astronomy & Astrophysics published research, according to which the phosphine content of 20 billionths is not in line with previous observations. Astronomers Therese Encrenazin a research team led by Venus observed Venus with an infrared telescope in 2015, but no signs of phosphine were found at the time.
According to the researchers, the infrared telescope should have detected phosphine if its concentration in the atmosphere was more than five billionths.
Criticism in particular, data collected by the Alma radio telescope in Chile, which Greaves and colleagues had to correct due to loud noise. Such large corrections, according to critics, easily lead to erroneous results and thus reduce the reliability of the data.
The Greaves team found that the loud noise was due to telescope calibration errors. They re-analyzed their data and concluded that the concentration of phosphine in the Venus atmosphere would be much lower.
According to the group, it is still possible that the observed phosphine can be explained by biological processes. According to Greaves, the concentration is still higher than what could result from volcanic eruptions or lightning strikes, for example.
U.S. Space Administration NASA Planetary Scientist Geronimo Villanueva points out, however, that the observations of the telescopes can also be explained by the sulfur oxide, which makes up most of the cloud layer of Venus.
Free further studies on the amount or origin of phosphine cannot be ascertained. Both the Greaves group and other scientists have begun to set aside telescope time for further study of Venus.
In 2025, India plans to launch a sonar into the orbit of Venus, possibly accompanied by instruments for phosphine research. Nasa and the European Space Agency (Esa) have also said they are considering sending a sonar to our neighboring planet.