Rainbows on Venus are made of pure acid, and the way the colors spread out tells you exactly how much they’ll burn.
arXiv · March 18, 2026 · 2603.15629
The Takeaway
Since Venus has clouds of sulfuric acid instead of water, its rainbows follow different optical rules. Researchers calculated that the size of the gap between the two main bands of the rainbow changes based on the acid's concentration, effectively turning light into a natural chemical probe of the planet's atmosphere.
From the abstract
The mechanism of rainbow formation proposed by Descartes and Newton is analyzed. The parameters of rainbows on Venus are calculated using geometric optics. Assuming that solar radiation is refracted by spherical droplets of aqueous sulfuric acid solution, the angular dimensions of the primary and secondary rainbows are determined as functions of the solution's concentration. It is shown that changes in concentration have the greatest effect on the size of the Alexander's dark band, the angular d