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Scientists have identified the mechanisms of dusting the Martian atmosphere

(ORDO NEWS) — Between dust storms, the Martian atmosphere is replenished with dust due to sandstorms and strong winds blowing up along the slopes.

The Martian atmosphere is more than a hundred times thinner than Earth‘s, and the daytime sky on Mars must be very dark. In fact, it is reddish and quite bright. The best evidence of this is the Martian shadows: they are not jet black, but similar to the earth.

The color and brightness of the Martian sky is caused by dust. Sandstorms kick up a huge amount of dust into the air, and in the absence of rain, the atmosphere is not able to clear it.

Larger particles settle, and the smallest fraction, about one micrometer in size, remains hanging in the air and gives the sky a reddish color, and the Martian landscapes a slight haze.

Dust storms on the Red Planet have been known for a long time, but even they cannot explain why there is so much dust in the Martian atmosphere.

At the height of a dust storm, it becomes dark there, almost like at night: if a solar-powered lander gets to the epicenter and does not turn off due to a lack of solar energy, it will suffer from a lack of it for a long time due to a layer of dust that has fallen on the photocells.

The disappearance of the sun and the darkening of the sky during a sandstorm on Mars, shot by the Opportunity rover. The numbers at the top of the right figure are the measure of opacity. Adding a value by one means an increase in absorption by a factor of ≈2.718; a value of 4.7 corresponds to a 110 times reduction in direct sunlight

Many Martian robots suffered and died from dust storms, but one of them was equipped enough to solve the riddle with the help of his equipment.

An international team of scientists led by Claire Newman analyzed camera footage and meteorological data from the Perseverance rover and identified several types of phenomena that raise dust into the air during “calm” times, regardless of dust storms.

The original article with the results of the study and many graphs, charts and photos can be found here .

The first of these turned out to be sand devils, or dust devils, which are sometimes observed in dry weather on Earth, but are ubiquitous on Mars and grow to gigantic sizes.

In addition to taking photographs, Perseverance can detect dust devils based on wind gusts, atmospheric pressure surges, and analysis of sounds recorded by a microphone.

It turned out that they are formed on Mars even more often than previously thought: the rover registered in its immediate vicinity one vortex per Martian day.

Powerful dust vortex photographed by the MRO orbiter. The width of the vortex at the base is 140 meters, and the height of the top of the raised dust cloud, measured by the length of the shadow, is 20 kilometers (higher than almost all terrestrial clouds)

he second phenomenon is sharp local gusts of wind, which are formed when a powerful convective cell in the atmosphere, developing during solar heating, reaches the surface (an animation of its development is shown in the main figure).

These gusts are observed less often than tornadoes, but they reach a high power, due to which their contribution to the maintenance of dust suspension is comparable to the latter.

The third factor was regional winds moving up the slopes (upside slope winds). They are tied to large-scale features of the relief, repeat every day and also kick up dust into the Martian atmosphere.

It turned out that in Lake Jezero crater, where the rover operates, daytime winds are controlled by a powerful updraft going up the slope of the Isis Basin, which raises clouds of dust to a great height.

On Earth, the main contributors to weather variability are weather phenomena associated with water evaporation and precipitation (such as cyclones). On Mars, they are absent, and the same phenomena are repeated regularly from year to year.

If on any Martian “date” a temperature of minus 10 degrees Celsius at noon and a southwest wind of 15 meters per second were noted, then next year the weather will be the same on this day (if there is no sandstorm). This refers to regional winds that regularly raise dust.

Another factor influencing the frequency of dust storms may be a seasonal imbalance between solar heating and thermal energy emitted back into space, and scientists have previously found that the main source of dust on the Red Planet is the porous and soft volcanic rocks that make up the furrows of Medusa.


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