Russian physicists have discovered two types of dust in the atmosphere of Mars

    A group of French and Russian scientists, including three specialists from the MIPT Laboratory for Planetary Atmospheric Infrared Spectroscopy at the Moscow Institute of Physics and Technology (Ph.D. Anna Fedorova, Ph.D. Alexander Rodin and Dr. Ph.D. Oleg Korablev) published a scientific paper in the Icarus journal with the results of a large-scale study, during which for the first time the data of the SPICAM infrared and ultraviolet spectrometers of the Mars Express apparatus were simultaneously analyzed while sensing the atmosphere on the planet's limb. As a result, scientists were able to restore the radii and concentration of particles in the atmosphere of Mars at altitudes from 10 to 50 km. Measurements were carried out in the southern and northern hemispheres during the northern summer season.

    The results are interesting. It turns out that the dust in the atmosphere of Mars consists of two fractions, and at an altitude of 40–50 km an aerosol layer with an as yet unknown composition was found.

    IKI RAS press release

    The illustration shows how the SPICAM spectrometer obtains data on the Martian atmosphere by comparing spectrograms at different heights with the pure spectrogram of the Sun.

    As it turned out, two groups of particles are present in the Martian atmosphere. The first type of aerosol consists of larger particles of water ice (average radius 1.2 microns) and dust (0.7 microns). There are not very many of them: from 0.01 to 10 particles in a cubic centimeter. The second type is dust particles with a radius of several tenths and hundredths of a micrometer, which are much larger: from 1 to 1000 in a cubic centimeter, depending on the height.

    In the northern hemisphere, at high latitudes (from 60 degrees), the level of the “large” aerosol fraction extends to heights of 30 km, in the middle hemispheres it rises to 40–50 km, and above 20 km it is mainly ice water, and below it is dust. The particle radii are about 0.76 microns (dust) and 1.2 microns (water ice), and the concentration varies between 0.4–2 and 0.01–0.3 particles per cubic cm

    , respectively. There is much more “fine” dust more: at an altitude of 10 km, the amount reaches 10 thousand particles per cubic cm, and already at 30–35 km - 100 particles in the same volume. Its average size is enlarged from the pole to the equator: 0.039 microns at latitudes above 60 degrees and 0.048 is lower (average value 0.044 microns).

    In the southern hemisphere, as is known from other observations, the atmosphere as a whole is quite clean. The average size of large dust particles at latitudes above 50 degrees was 0.75 μm, and the number in a cubic centimeter varies from 0.1 to 2. The particles of water ice are larger - the radius is approximately 0.86 μm, the concentration varies from 0.005 to 0 , 05 in cubic cm. The average radius of fine dust is greater than in the north: 0.07 microns - and the concentration decreases with a height from 100 (per 35 km) to 0.6 particles (per 70 km) in cubic cm. At low latitudes the sky is almost clear and the concentration of aerosol is low.

    It is interesting, however, that in this region at altitudes of 40–50 km in the ultraviolet range an aerosol layer with an as yet unknown composition was found. If it is dust, then the particles are very small (0.06 microns), and their number in a cubic centimeter is very large - from 100 to 3000. In the case of particles of water ice, their size will be slightly larger, and the concentration, on the contrary, will be less. This layer can exist due to the global flow of warm air masses from the northern (summer) hemisphere to the southern hemisphere, where they cool and fall (the so-called Headley cell). This circulation is characteristic of a season close to the solstice in both hemispheres.

    From the RAS press release

    The concentration of particles in the Martian atmosphere is not high. By earthly standards, this is a clean atmosphere. Even in the most “dusty” regions of Mars, the concentration of particles is lower than in the air of an ordinary room until a dust storm begins.

    It is curious what role aerosols play in the climate system of Mars. The fact is that the composition of particles described above in the atmosphere cannot exist for a long time. Obviously, it is replenished from the outside. The source of new particles may be dust from the surface of the planet.

    The modern climate of Mars is interesting in itself, because it is the only planet among the earth's group with a condensed atmosphere, and the climate system is largely controlled by aerosol. In addition, the planet may have experienced catastrophic climate change and retained traces of the climate of a past era, scientists from the Moscow Institute of Physics and Technology suggest.

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