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On Earth, clouds usually form when water vapor creates droplets or ice crystals in the presence of tiny particles, such as dust or salt. The new study, published in Nature Geoscience, instead suggests AMEC could be forming through so-called homogeneous nucleation, where vapor changes directly into ice crystals on its own without any help from debris.<\/p>\n
\u201cIt\u2019s akin to droplets of condensation appearing in the middle of a room, rather than on a window,\u201d Hern\u00e1ndez-Bernal explained. \u201cIt\u2019s wholly unexpected.\u201d<\/p>\n
This phenomenon requires extreme conditions\u2014a sharp temperature drop of 30\u00b0 Celsius within 10 minutes and high relative humidity. The Arsia Mons volcano also plays a key role. When wind current hits the 65,000-foot-tall volcano, it creates a powerful wave that launches moist air high in the atmosphere in a matter of minutes.<\/p>\n
Scientists have assumed a similar phenomenon could occur in the upper atmospheres of other planets, including Venus and even Earth, but it has never been observed. That\u2019s not too surprising given the extreme air humidity required for this phenomenon, which is more than 100,000 times greater than any value measured on Earth.<\/p>\n
Before this modeling, it was not known that these humidity levels existed on Mars either. \u201cWe don\u2019t have nearly as much information about Mars\u2019 atmosphere as we do about Earth\u2019s, so reproducing the AMEC to this degree is a big success,\u201d said Hern\u00e1ndez-Bernal, adding, \u201cthe result is remarkable.\u201d<\/p>\n