Researchers have identified the mechanism behind the Arsia Mons Elongated Cloud (AMEC), a recurring weather phenomenon on Mars. The cloud forms daily during the planet's spring and summer seasons near the 20-kilometer-high Arsia Mons volcano, reaching lengths of up to 1,800 kilometers before dissipating within hours.
The study, published in Nature Geoscience on October 7, utilized data from the European Space Agency's Mars Express orbiter. Scientists found that standard meteorological models failed to replicate the cloud until they incorporated a theoretical process known as homogeneous nucleation, which has never been observed in any planetary atmosphere.
Unlike terrestrial clouds that form through heterogeneous nucleation—where water vapor condenses around particles like dust or pollen—AMEC forms as water vapor transitions directly into ice crystals. This process occurs within powerful atmospheric waves created as winds rise along the volcano's slopes, causing temperatures to drop by 30 degrees Celsius in 10 minutes.
The Mars Express orbiter, equipped with the Visual Monitoring Camera, the High Resolution Stereo Camera, and the OMEGA instrument, provided the necessary data to track the cloud's formation. Researchers suggest that the water vapor required for this phenomenon may originate from the atmosphere or from frost deposits on the volcano's peak.
