New evidence about the clouds of Venus
A recent analysis of aerosols in the clouds of Venus, based on data collected in 1978 during the Pioneer Venus mission, has revealed the presence of significant amounts of water and iron. This study, led by Rakesh Mogul, a professor in the Department of Chemistry and Biochemistry at California Polytechnic State University, Pomona, was published in the Journal of Geophysical Research: Planets.
According to the research team, the aerosols in Venus's clouds contain iron sulfates and sulfuric acid in comparable proportions, approximately 20% by mass, and an abundance of water more than three times that amount, reaching nearly 60% by mass. This new information challenges the traditional view that Venus's atmosphere is predominantly dry, suggesting instead a more complex aerosol composition.
The analysis is based on a re-examination of data from the Pioneer Venus spacecraft, which had lain forgotten for decades. Researchers found multiple lines of evidence supporting the idea that aerosols contain a significant amount of water and oxidized iron. This new perspective could change how we understand the chemistry of Venus's clouds and its potential habitability.
Forgotten data and new findings
The data used in this study comes from Pioneer Venus, which collected information as it descended through the planet's atmosphere. Among the instruments on board was the Large Hadron Collider's Neutral Mass Spectrometer, whose data were archived by NASA and virtually forgotten by the scientific community for years.
In 2021, during a conversation about the composition of Venus's clouds, Mogul and Sanjay S. Limaye, co-author of the paper and senior Venus scientist at the University of Wisconsin, Madison, decided to review the mass spectral data. Thanks to the collaboration of Limaye and Michael J. Way, a NASA scientist and co-author of the study, the dataset was rediscovered in NASA's Coordinated Space Science Data Archive and subsequently published online.
The team used an innovative approach to analyze the evolved gases, developing a new understanding of aerosol composition. This included reinterpreting results from other instruments on the probe and re-evaluating data from the Soviet Venera and Vega landers, which also studied Venus's atmosphere. Through these measurements, it was found that all the instruments had inadvertently collected aerosols and measured their composition.
As the PV Large Probe descended through Venus's increasingly hot atmosphere, the collected aerosols underwent thermal decay, releasing gases and compounds into the onboard instruments. These included water (H2O), sulfur dioxide (SO2), oxygen (O2), and likely iron oxide (Fe2O3). Using the mass spectrometer, these molecules were identified in the dataset as H2O+, SO2+, O2+, and FeO+.
In addition, the Venera and Vega probes, which also carried chemical sensors, measured a considerable amount of water in the clouds after capturing aerosols. Mogul emphasized that these direct measurements highlight the presence of water and iron deposits in the aerosols, suggesting that the iron could originate from the influx of cosmic material.
This previously unknown aerosol composition raises new considerations for cloud chemistry models and the debate about Venus's habitability. Research continues, furthering the exploration of the planet and its atmosphere.
The Pioneer Venus mission, which began in 1978, remains a valuable source of information about the planet, and the new findings could have significant implications for future research.
