Daily Martian cloud over Arsia Mons may form without dust, researchers say
Researchers led by Jorge Hernández-Bernal of Sorbonne Université, reporting in Nature Geoscience, say the Arsia Mons Elongated Cloud forms when water vapour freezes directly into ice without a dust particle to seed it. Simulations matched observations only after this process, called homogeneous nucleation, was included, according to the study. The cloud, up to 1,800 km long, forms each morning during the Martian dusty season and vanishes by afternoon.
Bottom line — If confirmed, the finding would be the first observation of homogeneous nucleation in a planetary atmosphere, with the team suggesting it may also occur on Venus and Earth.
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The cloud was first spotted in 2018 and forms around a volcano about 20 km tall, with the team's model requiring air to cool by around 30 degrees in ten minutes.
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Hernández-Bernal acknowledged the simulated cloud does not match every detail of the observations, and the team describes the result as strongly suggestive rather than measured.
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Heise, citing the research, notes that the process requires relative humidity more than 100,000 times levels typical in daily life on Earth.
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The Debrief reports the team considers the result a major advance given how little observational data exists on the Martian atmosphere compared with Earth's.
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Martin Cid Magazine reports that a finer dust population was tested as an alternative explanation and produced hazy patterns rather than the observed sharp tail, though direct measurements are lacking.
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Universal-Sci credits ESA's Mars Express, which can observe Mars in the morning, with enabling the cloud to be tracked over several years.
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Colin Wilson, ESA Mars Express project scientist, said the probe discovered the cloud and has monitored it for years, according to Martin Cid Magazine.
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Daily Mail reports the team will test whether the process is unique to Arsia Mons, though this follow-up work is attributed to Martin Cid Magazine rather than the Daily Mail.
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