Dust storm could cause perchlorate formation on Mars

Electrostatic discharges in a simulated Martian environment produce perchlorates – a potential source of energy for microbial life – at much greater abundances than the sun.

According to new research, the huge concentrations of a potential source of energy for life on the surface of Mars come from electricity generated during dust storms.

Perchlorate ions – composed of a chlorine atom and four oxygen atoms – are very toxic to many organisms, but a small number of microorganisms can use perchlorate as a source of energy. So, when the Phoenix Mars NASA locator discovered perchlorates in 2008 near its North Pole landing site, the discovery left scientists with a hope of eventually discovering Martian life.

Perchlorate is much more common on Mars than local geology suggests, a fact that has puzzled researchers for years. Mars contains about 10 million times more perchlorate in its soil than would naturally be generated by sunlight. Some researchers have previously suggested that lightning could produce perchlorates, but this has not been tested before.

While they were testing the idea of ​​lightning, researchers led by Zhongchen Wu (Shandong University, China) proposed a new idea – the electricity generated by dust storms – after creating an atmosphere simulator similar to that of Mars, presenting pressures and temperatures similar to those found on the red planet.

The Martian atmospheric pressure is less than 1% of that of the Earth. It is therefore unlikely that Mars will accumulate enough charged particles for lightning. However, Martian dust storms are plentiful and it is well known that dust devils on Earth create electric fields. Electrostatic discharges can also occur more easily on the red planet.

The researchers conducted experiments on electrostatic discharges at temperatures similar to those of Mars and at atmospheric pressure inside a closed chamber. They discovered that the interactions between discharged electrons and Mars-type gas molecules instantly generated free radicals, which then oxidized rock salt to create chlorate, sodium carbonate and. . . perchlorate. They also found that the yields of oxidized compounds from visible high electron density discharges were more than 1,000 times higher than those obtained by photochemistry in their simulator, which corresponds to 10 million times on the planet itself.

Their research was published online on October 15 in Letters of Earth and Planetary Science.

Louis Derry (Cornell University) explains that the authors have found a potentially viable way to produce perchlorate observed at the surface.

"The study presents a very interesting mechanism for generating these highly oxidized compounds on the Martian surface," says Derry, who did not participate in this research. "It has been difficult to reach the apparent production rate needed to explain the great abundance of these compounds on Mars using the same mechanism as on Earth, largely because the Martian atmosphere is too thin .. It is hoped that follow – up studies will develop the results of their experiments, in the Martian and surface atmosphere.

Co-author Alian Wang (University of Washington, St. Louis) said Sky and telescope that his team hopes one day to corroborate their theories with direct observations of electrostatic discharges on Mars.

There has not yet been a mission – but not for lack of a try. According to Mr. Wang, a payload was to land on NASA Mars Surveyor's canceled 2001 lander, while another crashed to the surface with the rest of the landing demonstrator. European ExoMars Schiaparelli 2016.

"No payloads for the measurement of the electric field were selected in the three short-term land / ground missions to Mars, namely US March 2020, ExoMars in Europe and Mars 2020 in China. So we have to wait, "she said in an email.

She also asked for more electric field measurements on other planetary bodies, in order to provide comparison measurements. Possible locations could be the Moon, Venus, and some of the larger moons of the Jupiter system.

Wang added that she had several other studies underway to learn more about electric fields on the Martian surface, as well as about the possibility of habitability. She recently received a grant from the NASA Solar System program to study electrostatic-induced chemistry in conditions similar to those of Mars and Venus.

She is also interested in the possibility of life, as she is currently conducting a study on how the relevant hydrated salts for Mars provide more information "on the potential paradise in the Martian subsoil" for microbes, added Wang.

Editor's Note: This story was updated on November 9 to clarify which molecules have been observed in electrostatic discharge experiments and what processes led to their creation..

Reference:

Z. Wu et al. "Formation of perchlorates on Mars thanks to plasma chemistry during dust." Letters of Earth and Planetary Science. October 15, 2018.