Astrobiologist Dr. Janusz Pętkowski from the Massachusetts Institute of Technology (MIT) was part of the team analysing the possible physical and chemical processes that could have led to the production of phosphine on Venus.

With the clouds having a phosphine concentration of about 20 parts per billion, the scientists conducted calculations to see if such amounts could originate from natural non-biological processes on the planet. Potential possibilities have included sunlight, minerals ejected from the surface, volcanoes and lightning strikes, but none of these can produce enough phosphine. It has been established that non-biological processes can be responsible for up to one thousandth of the amount of phosphine detected by telescopes.

On Earth, this gas is produced only industrially and by microbes that develop in an anaerobic environment. In order to produce the amount of phosphine observed on Venus, the Earth organisms producing this compound would need to work at about 10 percent of their maximum efficiency.

However, the researchers stress that the discovery does not automatically mean that alien life has been found on Venus. Dr. Pętkowski said: “The discovery of traces of phosphine is not conclusive evidence of extraterrestrial life. We will get this evidence when we send a spaceship to Venus, 'catch' life and then see it with the naked eye or under a microscope. 

“Regardless of whether phosphine is a sign of life or not, the detection of this gas on Venus is an extraordinary discovery and represents a breakthrough in the study of terrestrial-type rocky planets in our solar system.”

The incredible discovery was first spotted by the James Clerk Maxwell Telescope (JCMT) and then by the Atacama Large Millimeter/submillimeter Array (ALMA) network of radio telescopes in Chile, in which the European Southern Observatory (ESO) is a partner. Forty-five  ALMA antennas were used in the observations, and wavelengths of about 1 millimetre were analysed. Weather conditions were very good during the observation and Venus was placed at a suitable angle. 

While the data analysis was challenging (ALMA typically doesn't look for subtle signals in objects as bright as Venus), ultimately it was confirmed that both JCMT and ALMA saw the same thing: faint absorption from phosphine gas.

But if microbes do live in the clouds of Venus, this raises the question of how they can survive there. While the high clouds in the atmosphere of Venus have a temperature of about 30 degrees Celsius, their chemical composition is completely different to that of Earth's clouds. Clouds on Venus are not composed of droplets of liquid water, but droplets of concentrated liquid sulphuric acid with very little traces of water. The environment is incredibly acidic, about 90 percent is sulphuric acid. For comparison, on Earth we know microbes that can handle about 5 percent acid content in the environment.

Although space agencies have been considering new unmanned spacecraft missions to Venus for some time, Dr. Pętkowski says that to look for life in the clouds would need a dedicated mission, designed specifically for the purpose.

The research results have been published in the scientific journal Nature Astronomy and reported by the European Southern Observatory (ESO). An additional publication will appear soon in Astrobiology.

PAP - Science in Poland

cza/ agt/ kap/

tr. RL