Mars's oddest cloud may be even odder than we thought
a day ago
- Mars's Arsia Mons Elongated Cloud (AMEC) is a spectacular water-ice cloud that forms daily near the Arsia Mons volcano during southern hemisphere spring and summer.
- New research using Mars Express and advanced modeling found that the AMEC forms via homogeneous nucleation, where water vapor freezes directly into ice without dust or other particles.
- This is the first time homogeneous nucleation has been observed in a planetary atmosphere, requiring extreme humidity levels over 100,000 times those typical on Earth.
- The cloud forms when winds passing over the 20-km-tall volcano lift moist air rapidly, cooling it by 30°C in 10 minutes and triggering spontaneous ice formation.
- The modeling only matched observations when exotic physics, normally considered theoretical, was included, marking a major success for the simulation.
- Mars Express, with its high-resolution cameras and morning-orbit capabilities, was essential for discovering and monitoring the AMEC, which stretches up to 1,800 km daily.
- The findings suggest that unlikely atmospheric processes may also occur elsewhere in the universe, including on exoplanets.