In Martian dust storms, the interaction of dust particles may produce electric fields strong enough to induce continuous electromagnetic waves known as Schumann resonances.
Physicists from HSE University, the Space Research Institute, and MIPT have come to this conclusion.
Over the last decade, Mars has been the subject of intense research, with scientists considering prospective space missions to the planet. The ability to understand the Martian atmosphere improves the odds of such missions succeeding. The behaviour of dust particles and the plasma-dust system on Mars’ surface, in particular, should be considered while designing space missions.
During a Martian dust storm in 2009, NASA’s Deep Space Network’s 34-meter radio telescope detected non-thermal microwave radiation. At frequencies of 7.83 Hz, 14.1 Hz, and 20.3 Hz, properties of Schumann resonances were discovered in the observed radiation spectra.
The role of dust and dust plasma in the stimulation of ultra-low-frequency (below 100 kHz) standing electromagnetic waves on Mars was investigated by researchers from HSE University, the Space Research Institute, and MIPT. This phenomena has been known as Schumann resonances since the mid-1950s, named after Otto Schumann, an Austrian scientist who was the first to analyze standing electromagnetic waves in an Earth-ionosphere resonator.
The Earth and its ionosphere act as a massive spherical resonator for electromagnetic waves, with the cavity filled by a weakly electrically conductive material. An electromagnetic wave that evolves in this medium can exist for a long period if it travels around the Earth and resonates with itself.
On Earth, thunderstorm charges in the spherical cavity between the planet’s surface and the lower layers of the ionosphere are thought to create Schumann resonances.
The researchers looked at the process that assures power loading in the Schumann resonator. Electrical discharges found revealed to be a ‘good candidate.’ However, unlike Earthly lightning, these electrical discharges have a distinct nature. Lightning, as we know it on Earth, is not typical of the Martian environment, which is characterized by dust swirls, sometimes known as ‘dust devils.’ They’re little storms with a diameter of roughly 100 metres that last a few minutes. As a result, the rare and dry Martian atmosphere lacks analogues to Earthly meteorological clouds, yet dust events play an essential role.
The process of charging dust particles in the Martian atmosphere is similar to that of volcanic clouds on Earth: two particles of the same material contact, and the smaller one receives a negative charge, while the larger one receives a positive charge. The larger positively charged particles settle in the lower regions of dust swirls due to gravity, while the lighter negatively charged particles stay in the upper part. Charges separate, perhaps resulting in an electrical discharge.
However, the paper’s authors note that there is currently no unambiguous experimental evidence to support the existence of electric discharges in Mars’ atmosphere. The higher layers of the atmosphere are frequently studied by orbital modules studying Mars, whereas the lower layers stay outside their monitoring zone. To determine whether or not there are Schumann resonances on Mars, the electric fields on the planet’s surface must be measured.
There are now no such initiatives planned, but the second stage of the ExoMars mission, which is set to launch in the second half of 2022, will almost certainly contribute to these research.
The study was published in Icarus journal.
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