Mars's strange cloud forms through exotic physics never before observed

Summarised from 2 outlets · Updated 8 Oct, 18:13 · Archive

A massive cloud on Mars forms through a process previously thought to exist only in theory.

Scientists have discovered how Mars's largest cloud forms through a process previously thought to exist only in theory. The Arsia Mons Elongated Cloud stretches up to 1,800 kilometres and appears each spring and summer in Mars's southern hemisphere, emerging downwind of the 20-kilometre-tall Arsia Mons volcano. It grows and fades each day, repeating this cycle every morning for several months.

Researchers using the European Space Agency's Mars Express spacecraft and meteorological modelling found the cloud forms through homogeneous ice nucleation. This is a process in which water vapour freezes directly into ice particles without first condensing on dust or other material. When winds flow past Arsia Mons, the volcano's bulk triggers a powerful wave that lifts moist air rapidly, cooling it so much that ice crystals form directly.

Jorge Hernández-Bernal, lead author of the study, said that to model the cloud's formation, researchers needed to include 'exotic physics – physics that, while included in textbooks, is treated as theoretical and usually thought not to happen in nature. It certainly hasn't been seen in action before.' He added: 'Once we included this physics in our simulations, the AMEC emerged just as we hoped.' The findings have been published in Nature Geoscience.

How it is being reported

• Scientist explore the ‘exotic physics’ behind Mars’ ‘oddest cloud’Space scientists have said that Mars’s "oddest cloud" may be even odder than they thought.New York Post · 8 Oct, 17:54
• Mars’s strangest cloud is even weirder than we thought, scientists sayMartian surface has objects with ‘exotic physics’, researchers sayIndependent Tech · 7 Oct, 16:25

In this story: Arsia Mons · Mars · Jorge Hernández-Bernal · European Space Agency · LMD/CNRS/Sorbonne Université

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