(ORDO NEWS) — Mars Express has shown that cloud structures form on Mars, reminiscent of those found in tropical regions of our planet.
Earth and Mars have completely different atmospheres. The dry, cold atmosphere of Mars is almost entirely carbon dioxide, while Earth’s is rich in nitrogen and oxygen.
Although they are very different from each other, their cloud structures have been found to be remarkably similar, indicating similar formation processes.
Scientists studied two dust storms that occurred near the north pole of Mars in 2019. Two cameras aboard Mars Express – the Visual Monitoring Camera (VMC) and the High Definition Stereo Camera (HRSC) – along with the MARCI camera aboard NASA’s Mars Reconnaissance Orbiter captured the storms from orbit.
A sequence of VMC images shows that storms appear to wax and wane in repeated cycles over several days, showing similarities and shapes. Spiral shapes are especially noticeable in HRSC images.
The length of the spirals is from 1000 to 2000 km, and their origin is the same as that of extratropical cyclones observed in the middle and polar latitudes of the Earth.
The images show that Martian dust storms are composed of evenly spaced cloud cells. A similar texture is also seen in clouds in the Earth’s atmosphere.
The familiar textures are formed by convection, in which hot air rises because it is less dense than the colder air that surrounds it.
Here we can observe closed convective cells with cloudiness in the center and cloudless space on the periphery.
On Earth, rising air contains water, which condenses to form clouds. Dust clouds captured by Mars Express show the same process, but on Mars, the rising columns of air contain dust, not water.
The sun heats the dusty air, causing it to rise and form dust cells. The cells are surrounded by areas of settling air that contain less dust. This results in a grainy pattern.
By tracking the movement of the cells, the wind speed can be measured. The wind blows over cloudy objects at speeds up to 140 km/h.
The results of the measurements showed that the dust can rise about 6-11 km above the surface, and the cells have horizontal dimensions of 20-40 km.
This organized cellular convection is not unique to Earth and Mars: Venus Express observations of the Venusian atmosphere show similar patterns.
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