Overview
- The new paper, published Wednesday, October 7, 2026, finds that computer models only reproduce the Arsia Mons Elongated Cloud when they include homogeneous nucleation, meaning water vapor turns straight into ice without needing dust or other particles.
- The Arsia Mons Elongated Cloud is a seasonal dawn phenomenon that appears every spring and summer in Mars’s southern hemisphere and can stretch about 1,100–1,800 kilometres downwind of the 20 km Arsia Mons volcano before dissipating later that morning.
- Researchers say the cloud forms when strong winds push moist air rapidly up the volcano’s slopes, cooling parcels by roughly 30°C in about 10 minutes and producing extreme supersaturation that the team estimates could be as high as 100,000 times typical Earth surface humidity.
- The model reproduces many observed AMEC features using Mars Express data from VMC, HRSC and OMEGA, but important mismatches remain and authors call for targeted orbital observations and improved microphysical measurements to confirm the hypothesis.
- If confirmed, the result would expand how scientists model clouds on other worlds and exoplanets and it highlights Mars Express’s unique role in observing short-lived morning phenomena for use in refining planetary atmospheric physics.