Signs of biologically relevant chemicals, including phosphine, have been found in the clouds of Venus by a team led by Rakesh Mogul, professor of biological chemistry at Cal Poly Pomona. The data was discovered in archived data from NASA’s Pioneer Venus Multiprobe, which arrived at Venus and collected data almost 42 years ago.
Re-examining results from the Large Probe Neutral Mass Spectrometer (LNMS), which measured Venus’ atmospheric composition while descending to the surface in 1978, the team discovered chemical signatures in the middle clouds that support the presence of phosphine, hydrogen sulfide, nitrous acid, nitric acid, hydrogen cyanide, carbon monoxide, ethane, and potentially ammonia and chlorous acid.
The study, “Venus’ Mass Spectra Show Signs of Disequilibria in the Middle Clouds,” was published today in Geophysical Research Letters.
Mogul and team indicate that the trace chemicals found serve as signs of redox disequilibria, which illuminate the presence of undiscovered chemistries, and also lends support to Venus’ clouds being a habitable zone for microorganisms.
The re-examination of the data reveals biologically relevant chemicals such as a key component for anoxygenic photosynthesis (nitrite/nitrous acid), all major constituents of the terrestrial nitrogen cycle (nitrate/nitric acid, nitrite/nitrous acid, ammonia, and N2) and a potential signature for anaerobic phosphorus metabolism (phosphine).
Among the chemicals making up the redox disequilibria is phosphine. Phosphine was recently detected through remote means by Jane Greaves and colleagues. Since then, the potential presence of phosphine, along with its interpretation as a potential signature for life, as was widely reported in the media, has been questioned by many. This is the first study to provide supportive evidence.
Mogul and team showed that the middle clouds harbor a heterogeneously mixed phosphorus-bearing gas, with phosphine being the simplest gas that best fit the mass data. “In the data, we see masses for the parent ion for phosphine, most of the fragment ions, and then atomic phosphorus, at an altitude of 51-55 km,” says Mogul. “No other phosphorus chemicals fit the data as well as phosphine, especially when considering the mild temperatures and pressures in the middle clouds, where many phosphorus species would not be gases.”
The LNMS was designed to target gaseous molecules in the atmosphere that are neutral in charge; phosphine matches this profile since it is a neutral phosphorus-bearing gas. The LNMS data consisted of ion counts across 232 preselected mass positions between 1 – 208 atomic mass units (amu).
The co-authors of the study are Sanjay S. Limaye (University of Wisconsin, Madison), Michael Way (NASA Goddard Institute for Space Studies) and Jaime A. Cordova (University of Wisconsin, Madison).
This work was made possible by the commitment of NASA to archive mission data. To the team’s knowledge, this study represents the first example of archived NASA data being used to extract such novel information. The Pioneer Venus Multiprobe mission data were the first to be archived by the Pioneer Venus project. The Pioneer Venus project data were subsequently incorporated into the National Space Science Data Center Archive, before NASA implemented the Planetary Data System.