An international team in which the University of the Basque Country (EHU) scientists Ricardo Hueso and Agustín Sánchez- Lavega are collaborating has discovered electrical discharges in the Mars atmosphere for the first time. The discovery, published in the journal Nature, was made by analysing sounds from the atmosphere of the red planet obtained by the Perseverance rover of the NASA Mars 2020 mission.

What is more, the electrical activity is very different from that on Earth. “On Earth, atmospheric electricity is dominated by the build-up of charge in clouds and storms and is violently discharged in the form of lightning. On Mars, atmospheric electricity is dry and is produced by collisions between dust particles in whirlwinds and dust storms, resulting in much smaller discharges than on Earth,” explained Ricardo Hueso.

The Perseverance rover, the core component of the Mars 2020 mission, landed in the Jezero Crater region on 18 February 2021 with the aim of exploring that region and collecting selected samples from the surface of Mars. These samples will be brought back to Earth in the future and will be used to search for possible signs of past life on the red planet. Perseverance's scientific instruments include a microphone associated with its Supercam instrument, in addition to a series of meteorological sensors that make up the MEDA weather station. This station was built by the Centro de Astrobiología (CAB) in Madrid, JPL in the United States and the Finnish Meteorological Institute (FMI) in Helsinki. One of the research groups that make up the MEDA scientific team is the Planetary Sciences Group at the Faculty of Engineering - Bilbao (EHU).

Perseverance has not only recorded the sounds of the discharges, but also their electromagnetic effects, which were also picked up by one of the microphone circuits. MEDA has enabled the research team to determine that these discharges occur when there are whirlwinds or dust storms. The study estimates that these discharges are not very long (tens of centimetres) compared with the hundreds of metres of lightning that occur during terrestrial storms.

“With its thin atmosphere of carbon dioxide, Mars is a cold, dry dusty world, where the wind is sometimes very strong, blowing in gusts and creating whirlwinds and rising dust bubbles. It can form fronts of giant storms hundreds of kilometres long, which sometimes cover the entire planet in dust. So we are expecting the hitherto elusive electrical discharges to be particularly numerous when these environmental conditions occur,” added Agustín Sánchez-Lavega.

The discovery of this phenomenon, known as “triboelectricity”, which is dominated by collisions between dust particles, is opening new doors for research on Mars. Electrostatically charged dust can “electrically levitate” large dust storms on Mars and promote their formation. It can also adhere to surfaces and accumulate significant loads, posing a risk factor for future manned missions. The electrical discharges may also have an effect on the chemistry of the atmosphere by generating oxidizing material that in the long term contributes to the elimination of organic substances from the surface and hinders the search for evidence of past life on the planet. In any case, “the study opens the door to numerous questions about the effects of natural electricity on the atmosphere of Mars”, concluded the EHU scientists.