Solar superstorm hit Mars: ESA spacecraft reveal orbital disruptions and a sudden spike of electrons in the atmosphere
The largest solar storm that hit Earth in May 2024 in more than two decades also left a strong mark on Mars, and a new analysis of European Space Agency data shows that the Red Planet’s response was exceptionally intense. While on Earth the storm triggered auroras visible unusually far south, even above parts of Mexico, on Mars the same wave of solar activity led to disruptions on spacecraft, a sharp increase in radiation and dramatic changes in the upper layers of the atmosphere. According to results published by researchers associated with the Mars Express and ExoMars Trace Gas Orbiter missions, this was the strongest recorded response of the Martian ionosphere so far to this type of space weather. This has also opened a new insight into how the Sun can shape conditions on a planet that does not have a global protective magnetic shield like Earth.
The episode itself was not merely another interesting astronomical event. For scientists monitoring Mars, it served as a rare natural experiment in real time. Two ESA orbiters, Mars Express and ExoMars TGO, found themselves in the right place at the right moment and recorded the direct consequences of a powerful solar strike. The radiation monitoring instrument on TGO registered a dose equivalent to approximately 200 normal days of radiation in just 64 hours. At the same time, both spacecraft recorded computer errors, which is a typical consequence of intense space weather, when high-energy particles can temporarily disrupt the operation of electronics. According to ESA, the systems recovered quickly precisely because they were designed to operate in such conditions.
What happened above Mars
A new study published on 06 March 2026 in the journal
Nature Communications shows that the upper atmosphere of Mars was literally flooded with electrons during this superstorm. The lead author of the research, Jacob Parrott, an ESA researcher and associate of Imperial College London, described this response as the largest ever recorded on Mars after a solar storm. The changes were neither symbolic nor marginal. In two atmospheric layers, at altitudes of approximately 110 and 130 kilometres, the number of electrons increased by about 45 percent and as much as 278 percent, respectively.
These figures are important because the Martian ionosphere, that is, the electrically charged part of the upper atmosphere, plays a crucial role in the transmission of radio signals, the interaction of the planet with the solar wind and the gradual loss of atmosphere into space. When the number of charged particles in that area suddenly increases, the way radio waves refract, weaken or become completely blocked changes. This is not merely a theoretical issue for laboratory analyses. It is a practical problem for future missions, for orbiters that relay data and for instruments that use radar to study the surface and subsurface of Mars. If the upper atmosphere is too saturated with electrons, the signals used to investigate the ground or communicate with robots on the surface can be seriously weakened.
That is exactly why scientists are viewing this event as both a warning and an opportunity. A warning because it confirms how powerful solar eruptions can destabilise technological operations around a planet without a global magnetosphere. An opportunity because data this rich help us understand more precisely the mechanisms by which Mars has been losing its atmosphere and water over billions of years. NASA’s MAVEN mission has already shown for years that the solar wind and solar storms accelerate the stripping of particles from the upper layers of the Martian atmosphere, and the new ESA results add a more detailed insight into the ionosphere’s immediate response to extreme conditions.
Why Mars reacted differently from Earth
The same solar event had very different consequences on Earth and on Mars. On Earth, in May 2024, a G5-level geomagnetic storm was recorded, the highest level on NOAA’s scale, for the first time in more than 20 years. The storm triggered spectacular auroras at unusually low geographic latitudes and caused disruptions in parts of communication and navigation systems. However, Earth has a strong global magnetic field that deflects or stops a large portion of energetic particles before they directly hit the atmosphere. Some of those particles are directed toward the poles, where auroras form, but the rest of the planet remains significantly better protected than Mars.
Mars does not have such protection. It possesses only localised remnant magnetic fields in its crust, but not a global magnetic shield that would envelop the entire planet. Because of that, its upper atmosphere is much more directly exposed to the onslaught of solar wind, X-ray radiation and particles from coronal mass ejections. When such material reaches Mars, neutral atoms in the atmosphere collide with energetic particles, lose electrons and create an enhanced population of charged particles. That is exactly what was recorded during the analysed superstorm: the atmosphere did not merely heat up or become mildly disturbed, but was chemically and electrically strongly reshaped over a relatively short period.
That difference between the two planets is important from a broader scientific perspective as well. Comparing Earth and Mars allows a better understanding of space weather in the Solar System and more precise assessments of risk for future crewed missions. On Earth, powerful solar storms can threaten satellites, energy infrastructure, radio communications and navigation. On Mars, similar events could have even more direct consequences for electronics, communication links, radar research and the radiation exposure of astronauts who may one day stay there.
The new technique that enabled detailed measurement
One of the most important elements of this research is not only the storm itself, but also the way it was observed. Scientists used a technique known as radio occultation, which ESA has been developing in increasingly advanced form in recent years for the study of the Martian atmosphere. In this case, Mars Express sent a radio signal toward TGO at the exact moment when one spacecraft was disappearing behind the Martian horizon. Along that path, the signal passed through layers of the atmosphere and was bent, that is, refracted. From those changes, researchers can calculate electron density and other properties of the atmospheric layers through which the signal passed.
Such a method is not new in planetary science, but its application between two spacecraft in orbit around Mars represents an important technological and operational step forward. Classical radio occultation has been used for decades in such a way that a spacecraft sends a signal toward Earth, and changes in the signal are used to analyse a planet’s atmosphere. However, only in recent years has ESA begun to use more systematically an approach in which two orbiters exchange signals with each other while circling the same planet. This provides different measurement geometry conditions and opens the possibility of more detailed monitoring of parts of the ionosphere that were previously harder to access.
Jacob Parrott and his collaborators further confirmed the results by comparing them with data from NASA’s MAVEN mission, specialised precisely for studying the upper atmosphere of Mars and its relationship with the solar wind. This is important because multiple independent measurement sources increase the reliability of the conclusion that the May superstorm truly caused record changes in electron density. At the same time, it also shows the value of international cooperation in space exploration: without simultaneous observations by ESA and NASA missions, the overall picture of the event would have been significantly poorer.
A very fortunate moment for science
The study of space weather also carries one basic problem: the Sun does not act on schedule. Solar flares, bursts of energetic particles and coronal mass ejections occur unpredictably, and missions around other planets cannot constantly be in the ideal position for every measurement. Because of that, data like these are often the result of a combination of good preparation and a great deal of luck. According to ESA, scientists used the new technique just ten minutes after a powerful solar flare hit Mars. Since such observations on Mars are currently carried out only a few times a week, the coincidence of the observation moment and the impact of the solar storm was exceptionally favourable.
In doing so, the team managed to capture the consequences of three different solar events that were part of the same storm, but differed from one another in what they were ejecting into interplanetary space. One event referred to a flare, that is, a powerful pulse of radiation, the second to a burst of high-energy particles, and the third to a coronal mass ejection, a huge eruption of magnetised plasma from the Sun’s outer atmosphere. Together, these processes sent toward Mars a combination of X-ray radiation, fast particles and magnetically carried plasma material. When that wave reached the planet, the consequences quickly became apparent in the ionosphere.
It is precisely in such moments that it becomes clear why predicting and monitoring space weather are becoming increasingly important. This is not a discipline reserved only for theoretical astrophysics. It is an area that directly affects spacecraft safety, the planning of communication links, instrument design and future human missions. ESA is therefore also developing broader capacities for monitoring solar activity, and the experience from May 2024 also served as a reminder of how far-reaching the consequences of one exceptionally active solar period can be.
What this means for future research and possible human missions
The results of the new work do not speak only about one dramatic event in the past, but also about the future of Mars exploration. If a powerful solar storm can in less than three days produce a radiation dose comparable to 200 normal days and simultaneously cause computer errors on orbiters, then every serious strategy for longer-term robotic and human operations must take such episodes into account. This applies to the design of electronic systems, crew protection, the planning of communication windows and the use of radar or other instruments sensitive to the state of the ionosphere.
The issue of radiation safety is especially important. ESA had already previously warned that the journey of astronauts to Mars and their stay in its environment would involve serious exposure to radiation, and events like these further confirm that the danger does not come only from prolonged background radiation but also from short yet very intense solar episodes. For future bases on the surface of the planet, this means that shielding systems, timely warnings and operational protocols will have to be an integral part of the mission, not an afterthought.
At the same time, the scientific value of such superstorms remains enormous. Mars today has a thin envelope, a cold and dry surface, and only fragments of the conditions that may once have allowed the stable presence of liquid water. One of the key questions of planetary science is how that planet lost a large part of its atmosphere over time. Every new confirmation that solar activity can strongly pump energy and particles into the upper layers of the atmosphere helps reconstruct the long-term story of the climatic and atmospheric evolution of Mars. In other words, observing today’s solar storms also helps us understand why ancient Mars became the world we know today.
The Sun as a constant factor of risk and knowledge
The story of the solar superstorm that struck Mars shows how closely the exploration of other worlds today is connected to understanding the Sun. Mars Express, launched back in 2003, and ExoMars TGO, which has been orbiting Mars since 2016, in this case served not only as observers but also as sensitive witnesses of a violent space environment. Their temporary disruptions are a reminder that not even the most advanced technology is beyond the reach of solar activity. But the fact that the instruments continued to work while recording such a valuable set of data also shows the other side of the story: every such storm is simultaneously a threat and a source of knowledge.
For scientists, it is particularly important that they have now better understood how quickly and how strongly the Martian ionosphere can react to an extreme space event. For engineers, the important confirmation is that even short-lived episodes can change the conditions for radio links and sensitive electronics. And for the wider public, this is yet another reminder that space is not a quiet and static place, but a dynamic environment in which the Sun constantly shapes the fate of planets. In the case of Mars, the May 2024 storm did not merely cause short-term chaos in the upper atmosphere, but also offered one of the clearest insights so far into what the moment looks like when a solar superstorm directly strikes an unprotected planet.
Sources:- - European Space Agency (ESA) – official announcements about the May solar storm, the Mars Express and ExoMars TGO missions, and the observed effects on Mars (link)
- - Nature Communications – scientific publication on the effect of the solar superstorm on the Martian ionosphere and the record increase in electron density (link)
- - NASA Science – overview of the strongest solar storm to hit Earth in two decades and its effects on the space environment (link)
- - NOAA Space Weather Prediction Center – official confirmation of G5 geomagnetic conditions during the May 2024 solar storm (link)
- - NASA JPL / MAVEN – observations of aurora and the consequences of the solar storm on Mars in May 2024 (link)
- - ESA blog To Mars and Back – explanation of the technique of mutual radio occultation between Mars Express and TGO (link)
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