Harvard Scientists Reconsider the Possibility of Life on Venus


Researchers at Harvard, the Paris Observatory, and MIT, among other institutions, have found that Venus’s atmosphere may not contain phosphine gas, a possible indicator of life, contradicting the results of a study published last month.

The original study was published in the journal Nature Astronomy on Sept. 14. At the time, researchers — including scientists from Harvard and MIT — reported the presence of phosphine gas in Venus’s atmosphere. The study received national media attention for its conclusion that the phosphine gas could indicate the presence of life on Earth’s neighboring planet.

Following the study’s publication, however, multiple research teams reanalyzed the data and concluded that the phosphine levels on Venus are lower than originally reported.

Thérèse A. Encrenaz, an astrophysicist at the Paris Observatory who led one of the subsequent studies, said her research suggests levels of phosphine on Venus are, at most, four times lower than what the original study suggested.


Encrenaz said her findings cast doubt on the legitimacy of the original research.

“Honestly, among all the people I have met who are specialists of millimeter spectroscopy, none of them believe the observation,” Encrenaz said.

Clara Sousa-Silva, a researcher at the Harvard-Smithsonian Center for Astrophysics who was part of the original study and Encrenaz’s reanalysis efforts, as well as other ongoing studies, said the discrepancies were unsurprising.

Contrasting analyses of the same data are normal and expected, according to Sousa-Silva, especially given the complicated nature of the data.

“It's noisy, delicate, complex data. So it's very hard to see the signal unless you clean up the noise,” Sousa-Silva said.

John M. Carpenter, an observatory scientist at ALMA Observatory who helped collect data for the original paper, said he had been concerned about the legitimacy of the study’s claims about phosphine. Carpenter said he was not involved in the data analysis.

“That was just a concern, as I had not processed the data myself, so I couldn’t prove it one way or the other,” Carpenter said.

Encrenaz and Carpenter also questioned whether the detection of phosphine necessarily means there is life on Venus.

“It’s completely premature to talk about life,” Encrenaz said. “Even if it had been demonstrated that phosphine is present, you could not just jump and say that this is because of life.”

Sousa-Silva claimed, however, that scientists have yet to find another explanation for phosphine on Venus besides evidence of life.

“We have no known explanation for phosphine on Venus, other than by analogy with anaerobic life on Earth. We know a Venusian life form could happily make it the same way life on Earth happily makes it as long as it’s anaerobic,” Sousa-Silva said.

Sousa-Silva said the contradictory follow-up studies were part of the process of scientific discovery.

“I would like to at least encourage the scientific community but also the public in general to not think that conflicting analyses are controversial,” Sousa-Silva said. “That is literally what the scientific method would have you do. And hopefully these different analyses will eventually converge into agreement.”

Correction: November 2, 2020

A previous version of this article incorrectly stated that Clara Sousa-Silva, a researcher at the Harvard-Smithsonian Center for Astrophysics, said given the currently limited research on phosphine, the most likely conclusion is that phosphine is indicative of life on Venus. In fact, she said scientists have yet to find another explanation for phosphine on Venus besides evidence of life.