A 1,600 km long cloud formation on Mars and a mechanism never before observed on Earth.
There's a cloud on Mars that I find truly fascinating: it's about 1,600 km long, sometimes reaching 1,800 km (about 1/12 of the planet's circumference), appearing almost every morning and then completely disappearing within a few hours.
Scientists call it the Arsia Mons Elongated Cloud (AMEC), because it forms above Arsia Mons, a dormant volcano about 20 km high in the Tharsis region, south of the Martian equator. The Mars Express orbiter of the European Space Agency (ESA) discovered it in 2018, and since then, simulations have yet to reproduce how it comes into existence.
In terms of its shape, the AMEC is an orographic cloud: strong winds push moist air over the high mountain, similar to the Levanter clouds that sometimes form on the Rock of Gibraltar. But the key difference lies elsewhere. On Earth, clouds typically form through heterogeneous nucleation: water vapor condenses into ice around dust particles, salt, pollen, or soot. The Martian atmosphere is full of dust, yet this process doesn't seem to be happening here.
In a paper published on October 7th in Nature Geoscience, a team led by planetary scientist Jorge Hernández-Bernal (University of the Basque Country, Spain) suggests that the water vapor in the AMEC transforms directly into ice crystals without any "nuclei." They call this homogeneous nucleation, a process that has never been observed in the atmosphere of any planet. When they incorporated this mechanism into their Martian weather models, they were able to accurately reproduce the characteristics of the cloud.
The conditions required for this to happen are also quite special: winds blowing up the slopes of Arsia Mons (more than twice the height of Mount Everest) create a rapid updraft, and the temperature can drop by as much as 30 degrees Celsius in just 10 minutes. The water vapor may come from the atmosphere, and partly from the thick layer of frost that covers the mountain peak.
What I find most interesting about this story is that what seems like an "impossible" phenomenon forces us to abandon familiar meteorological principles in order to find an explanation. The Mars Express is one of the few spacecraft that can observe the summit of Arsia Mons during the day, so its data is crucial to this discovery.
Source: VnExpress
Scientists call it the Arsia Mons Elongated Cloud (AMEC), because it forms above Arsia Mons, a dormant volcano about 20 km high in the Tharsis region, south of the Martian equator. The Mars Express orbiter of the European Space Agency (ESA) discovered it in 2018, and since then, simulations have yet to reproduce how it comes into existence.
In terms of its shape, the AMEC is an orographic cloud: strong winds push moist air over the high mountain, similar to the Levanter clouds that sometimes form on the Rock of Gibraltar. But the key difference lies elsewhere. On Earth, clouds typically form through heterogeneous nucleation: water vapor condenses into ice around dust particles, salt, pollen, or soot. The Martian atmosphere is full of dust, yet this process doesn't seem to be happening here.
In a paper published on October 7th in Nature Geoscience, a team led by planetary scientist Jorge Hernández-Bernal (University of the Basque Country, Spain) suggests that the water vapor in the AMEC transforms directly into ice crystals without any "nuclei." They call this homogeneous nucleation, a process that has never been observed in the atmosphere of any planet. When they incorporated this mechanism into their Martian weather models, they were able to accurately reproduce the characteristics of the cloud.
The conditions required for this to happen are also quite special: winds blowing up the slopes of Arsia Mons (more than twice the height of Mount Everest) create a rapid updraft, and the temperature can drop by as much as 30 degrees Celsius in just 10 minutes. The water vapor may come from the atmosphere, and partly from the thick layer of frost that covers the mountain peak.
What I find most interesting about this story is that what seems like an "impossible" phenomenon forces us to abandon familiar meteorological principles in order to find an explanation. The Mars Express is one of the few spacecraft that can observe the summit of Arsia Mons during the day, so its data is crucial to this discovery.
Source: VnExpress
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