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Arsia Mons cloud formation research on Mars

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2026-10-11 16:55 UTC → 2026-10-12 05:24 UTC · added ~~removed~~

Researchers have identified the mechanism behind the Arsia Mons Elongated Cloud (AMEC), a massive water-ice cloud formation on Mars that can reach 1,800 kilometers in length. First observed by the European Space Agency’s Mars Express orbiter in 2018, though documented as far back as the 1970s via NASA’s Viking 2, the clouds appear during the Martian spring and summer near the Arsia Mons volcano before evaporating within hours. Studies published in ‘Nature Geoscience’ indicate that the phenomenon is orographic, caused by intense winds striking the volcano's slopes and propelling moist air into the stratosphere. This process leads to rapid cooling, where temperatures can drop by approximately 30 degrees Celsius in less than ten minutes. This specific mechanism, while documented in theoretical textbooks, had never been observed in action within a planetary atmosphere until now. To explain the cloud's behavior, which traditional meteorological models failed to replicate, scientists utilized advanced modeling and data from Mars Express. The research, involving institutions such as Sorbonne University, suggests the clouds form through “homogeneous nucleation.” This is an “exotic” physical process where water vapor transforms directly into ice crystals without the dust or salt particles typically required for cloud formation on Earth. A team led by Jorge Hernández-Bernal from Sorbonne Université successfully used this process to model the cloud's unique structure, providing new insights into Martian atmospheric dynamics.

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