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Department of Earth Sciences

Synthesized false colour image of Venus, Credit: JAXA / ISAS / Akatsuki Project Team

Minerals present in the Venusian atmosphere could explain the colour and splotchiness of the planet’s clouds in the UV range say Cambridge researchers, solving a long-standing mystery.

Scientists know that Venus' clouds are mainly composed of sulfuric acid droplets with some water, chlorine, and iron — a mix that varies with height in the thick and hostile Venusian atmosphere. But, until now, scientists have been unable to identify what causes the strange patches and streaks on the clouds, only visible in the UV range.

In a new study published in Science Advances, researchers from the University of Cambridge synthesised iron-bearing sulfate minerals that are stable under the harsh chemical conditions in the Venusian clouds. Spectroscopic analysis revealed that a combination of two minerals, rhomboclase and acid ferric sulfate, can explain the mysterious UV absorption feature on our neighbouring planet.

“The only available data for the composition of the clouds were collected by probes and revealed strange properties of the clouds that so far we have been unable to fully explain,” said Paul Rimmer from Cambridge’s Cavendish Laboratory, and co-author of the study. “In particular, when examined under UV light, the Venusian clouds featured a specific UV absorption pattern.” The researchers wanted to know which elements, compounds, or minerals might be responsible for the observation.

The team synthesized several iron-bearing sulfate minerals in Professor Nick Tosca's aqueous geochemistry laboratory at Cambridge’s Department of Earth Sciences. By suspending the synthesized materials in varying concentrations of sulfuric acid, representing conditions in the Venusian atmosphere, and monitoring chemical and mineralogical changes, the team narrowed down the candidate minerals to rhomboclase and acid ferric sulfate.

At the Cavendish Laboratory, the spectroscopic features of the minerals were then examined under light sources specifically designed to mimic the spectrum of solar flares in Paul Rimmer and Samantha Thompson's FlareLab. A photochemistry lab at Harvard collaborated in the research by providing measurements of the UV absorbance patterns of ferric iron under the extreme acidic conditions in the Venusian clouds.

“The patterns and level of absorption shown by the combination of these two mineral phases are consistent with the dark UV-patches observed in Venusian clouds,” said lead author of the study, Clancy Zhijian Jiang, from Cambridge’s Department of Earth Sciences. “These targeted experiments revealed the intricate chemical network within the atmosphere, and shed light on the elemental cycling on the Venusian surface.”

“Venus is our nearest neighbour, but it remains a mystery,” said Rimmer. “We will have a chance to learn much more about this planet in the coming years with future NASA and ESA missions set to explore its atmosphere, clouds and surface. This study prepares the grounds for these future explorations.”


The research comes out of the newly established Origins Federation, which promotes such collaborative projects.

The research was supported by the Simons Foundation, and the Origins Federation.


Clancy Zhijian Jiang et al., ‘Iron-sulfur chemistry can explain the ultraviolet absorber in the clouds of Venus.’ Sci. Adv.10, (2024). DOI:10.1126/sciadv.adg8826



Adapted from a story published here.

Image: Processed using ultraviolet (365nm & 283nm) filtered images of Venus taken by Akatsuki on May 23 2018. Credit: JAXA/ISAS/DARTS/Kevin M. Gill.