Nature Geoscience

For decades, planetary scientists have puzzled over a thin, 1,800-kilometre-long cloud that appears every summer morning west of Mars’s Arsia Mons volcano. A new study published in Nature Geoscience proposes that the cloud forms through homogeneous nucleation, a process in which water vapour spontaneously freezes into ice without needing the dust particles that normally seed cloud formation. If confirmed, it would be the first known natural occurrence of a phenomenon long dismissed as a laboratory curiosity.