Mars Superstorm: ESA Orbiters Reveal Atmospheric Impact & Spacecraft Glitches

A recent solar superstorm, one of the largest in over two decades, didn’t just trigger spectacular auroras visible from Earth – it also delivered a significant jolt to Mars. Thanks to the European Space Agency’s (ESA) Mars Express and ExoMars Trace Gas Orbiter (TGO), scientists have been able to observe the event’s impact on the Red Planet’s atmosphere and spacecraft systems, revealing a dramatic surge in atmospheric electrons and some temporary glitches for the orbiting probes. The findings, published today in Nature Communications, offer a unique glimpse into how solar activity interacts with Mars, a planet lacking Earth’s protective global magnetic field.

Understanding the Solar Storm

The solar storm in question peaked in May 2024, and was notable for its intensity. As ESA explained, it was the biggest recorded in over 20 years, causing a significant disturbance in Earth’s magnetosphere and resulting in widespread auroral displays. This same storm propagated through the solar system, eventually reaching Mars. The TGO’s radiation monitor registered a dose equivalent to 200 “normal” days in just 64 hours, highlighting the storm’s energetic nature.

A Flood of Electrons in the Martian Atmosphere

The impact on Mars was particularly striking in its upper atmosphere. ESA Research Fellow Jacob Parrott, lead author of the Nature Communications study, described the event as “remarkable,” noting that Mars’s upper atmosphere was “flooded by electrons.” Specifically, the superstorm caused a dramatic increase in electron density in two layers of the Martian atmosphere, at altitudes of approximately 110 and 130 km. Electron counts rose by 45% in the lower layer and a substantial 278% in the higher layer – the highest concentrations ever observed in that region of the Martian atmosphere.

Radio Occultation: A Recent Perspective

To investigate these atmospheric changes, Parrott and his team employed a technique called radio occultation. Traditionally used to study planetary atmospheres by analyzing how radio signals bend as they pass through them, this method was adapted to utilize signals beamed between the Mars Express orbiter and the TGO. As TGO passed behind Mars from the perspective of Mars Express, the radio signal was refracted by the atmosphere, providing data on its composition and density. This data was then corroborated with observations from NASA’s MAVEN mission, which also measured electron densities.

Spacecraft Resilience and the Perils of Space Weather

The solar storm wasn’t without its challenges for the orbiting spacecraft themselves. Both Mars Express and TGO experienced computer errors due to the influx of energetic particles – a common hazard of space weather. Fortunately, both orbiters were designed with radiation-resistant components and systems for detecting and correcting these errors, allowing them to recover quickly. ESA notes that these systems are similar to those used to detect and fix errors on other missions, as described in their documentation on system fingerprinting.

Earth vs. Mars: A Tale of Two Atmospheres

The differing responses of Earth and Mars to the same solar storm highlight the fundamental differences between the two planets. Earth’s global magnetic field provides a significant shield, deflecting many solar particles and channeling others towards the poles, creating auroras. Mars, lacking this global magnetic field, is more directly exposed to the full force of solar activity. This exposure has implications for the planet’s atmosphere, as the continual stream of particles from the Sun is believed to be a major driver of atmospheric loss – a process that has already seen Mars shed much of its original atmosphere and water.

Implications for Future Exploration

Understanding how solar storms impact Mars is crucial not only for understanding the planet’s history but also for planning future missions. The study’s findings improve our understanding of how energy and particles are deposited into the Martian atmosphere, a key factor in atmospheric escape. The increased electron density in the upper atmosphere could interfere with radio signals used for radar-based exploration of the Martian surface, a consideration for mission planning.

The research also underscores the importance of continued space weather monitoring. ESA is planning to launch additional missions dedicated to observing the Sun and its activity, including Smile (scheduled for launch in 2026) and Vigil (2031), to provide more timely and accurate forecasts of space weather events.

Looking Ahead

Jacob and his colleagues were able to capture data from three distinct solar events – a flare of radiation, a burst of high-energy particles, and a coronal mass ejection (CME) – all part of the same superstorm. The timing of these observations was particularly fortunate, as the team was already conducting radio occultation measurements. Currently, they perform only two such observations per week, making the coincidence of the storm with scheduled measurements a stroke of luck. Further research will focus on refining these techniques and increasing the frequency of observations to better characterize the dynamic interaction between the Sun and Mars.