Arsia Mons cloud formation on Mars

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

Studies published in Nature and Nature Geoscience indicate that the cloud forms through ‘homogeneous nucleation.’ While Earthly clouds typically require particles like dust to act as condensation nuclei, the extreme conditions near the volcano allow water vapor to convert directly into ice. Lead author Jorge Hernández-Bernal noted that including this specific physics, which was previously considered unlikely under natural conditions, was necessary to reproduce the cloud in atmospheric models. Researchers highlighted that while these physical concepts exist in textbooks, they have not been observed in action within a planetary atmosphere until now.

The process is driven by strong winds hitting the volcano, which forces moist air upward rapidly. This creates a temperature drop of approximately 30 degrees Celsius within ten minutes and leads to atmospheric supersaturation levels 100,000 times higher than average conditions on Earth. These findings were supported by meteorological modeling and data from the European Space Agency’s Mars Express orbiter.