Arsia Mons cloud formation explained by exotic physics

Researchers have identified the physical mechanism behind the Arsia Mons Elongated Cloud (AMEC), a massive, recurring cloud formation on Mars. The cloud, which can stretch up to 1,800 kilometers, appears every morning during the Martian spring and summer near the 20-kilometer-high Arsia Mons volcano.

According to a study published in Nature Geoscience, the formation of the AMEC involves a process called “homogeneous nucleation.” Unlike clouds on Earth, which typically require dust, salt, or other particles to act as condensation nuclei (heterogeneous nucleation), the water vapor in this Martian cloud converts directly into ice. This phenomenon has never before been observed in a planetary atmosphere.

The process is triggered when strong winds hit the volcano, creating a wave that lifts moist air rapidly. This causes the temperature to drop by approximately 30 degrees Celsius within ten minutes, driving extreme humidity levels. The findings were made possible by combining data from the European Space Agency’s Mars Express orbiter with advanced meteorological modeling.