Solar Superstorm Struck Mars, Causing Dramatic Expansion of Its Atmosphere

In May 2024, Mars was hit by an extremely powerful solar storm, the effects of which were observed by an international fleet of orbiters and rovers. The event, which scientists refer to as a "superstorm," was one of the most powerful phenomena of its kind ever recorded on the Red Planet. The direct cause was a solar eruption that hurled a massive cloud of charged particles, known as a coronal mass ejection, towards Mars. When these particles reached the planet, they interacted with its thin, carbon dioxide-dominated atmosphere, causing it to swell and expand dramatically.

Mars, unlike Earth, lacks a global magnetic field that acts as a protective shield against the solar wind. Its weak, remnant magnetic field is scattered and does not form an effective barrier. As a result, the planet's atmosphere is directly exposed to bombardment by charged particles from the Sun, leading to its gradual erosion on a geological timescale. This process is considered one of the key factors that transformed Mars from a potentially warm and wet planet billions of years ago into the cold, dry desert we know today.

The impact of the storm resulted in a dramatic "swelling" of Mars's atmosphere. Its outer layers expanded, allowing atmospheric gas particles to escape more easily into space. The MAVEN (Mars Atmosphere and Volatile EvolutioN) orbiter, whose main task is to study this very atmospheric loss, observed significant changes in its upper regions. „This event gave us an unprecedented opportunity to observe how solar storms can affect the Martian atmosphere. We saw how many particles were blasted into space, helping us understand how Mars has been losing its atmosphere over billions of years.” — Principal Investigator of the MAVEN mission at NASA Simultaneously, the Curiosity rover, working in Gale Crater, recorded a record increase in radiation levels on the surface. The RAD (Radiation Assessment Detector) instrument recorded the highest doses since the vehicle landed twelve years ago.

300% — increase in the density of Mars's atmosphere

A particularly interesting aspect of the observations were changes in the Martian ionosphere, the charged layer of the atmosphere. The Trace Gas Orbiter, belonging to the European Space Agency (ESA), observed that under the influence of the storm, the ionosphere became ten times denser. This, in turn, caused disruptions in radio communication between Earth and vehicles on Mars, posing a practical challenge for mission control. Scientists emphasize that this event was a unique natural experiment. Thanks to coordinated observations from the rover on the surface (Curiosity), orbiters studying the atmosphere (MAVEN, Trace Gas Orbiter), and those monitoring radiation (Odyssey), it was possible to create a comprehensive picture of the storm's impact on different layers of the planet. This data is invaluable for understanding not only modern Mars but also the processes that shaped its climate in the past. Furthermore, it has direct implications for the future of space exploration. The May 2024 solar storm clearly showed how serious a threat radiation can be to astronauts during a long-term mission to Mars. The collected information will be used to improve spacecraft designs, surface habitats, and safety procedures that will protect crews from similar phenomena. This research is a key element of preparations by NASA and other space agencies for a crewed expedition to the Red Planet, planned for the 2030s.