Mars cloud formation study reveals unexpected physics

A new study published in Nature Geoscience suggests that the Arsia Mons Elongated Cloud (AMEC) on Mars forms through a process called homogeneous nucleation. Unlike clouds on Earth, which typically require particles like dust or salt to form droplets, this 1,800-kilometer-long ice cloud appears to form when water vapor transforms directly into ice crystals without any debris.

The phenomenon occurs near the 65,000-foot-tall Arsia Mons volcano during the Martian spring and summer. When wind currents hit the volcano, they create waves that launch moist air high into the atmosphere. This process requires extreme conditions, including a temperature drop of 30 degrees Celsius within 10 minutes and humidity levels more than 100,000 times greater than any measured on Earth.

Lead researcher Jorge Hernández-Bernal noted that while similar processes have been theorized for the atmospheres of Venus or Earth, they have never been directly observed. The ability to successfully model the AMEC provides significant new insights into the Martian atmosphere.