Solar Superstorm Bombarded Mars with 200 Days of Radiation in 64 Hours

The May 2024 solar superstorm was the biggest in over 20 years.

The May 2024 solar superstorm was the biggest in over 20 years. It lit up auroras as far south as Mexico on Earth — and it hit Mars just as hard.

ESA's Mars Express and ExoMars Trace Gas Orbiter were in the right place at the right time. Together, they measured a radiation dose equivalent to 200 normal days in just 64 hours.

"The impact was remarkable: Mars's upper atmosphere was flooded with electrons," said ESA Research Fellow Jacob Parrott, lead author of the study. "It was the biggest response to a solar storm we've ever seen at Mars."

The storm caused electron density to spike by 45% at 110 km altitude and a staggering 278% at 130 km — the most electrons ever recorded in that region of the Martian atmosphere.

Both orbiters experienced computer glitches during the storm, a known hazard of space weather. But they were built with radiation-resistant components and recovered quickly.

The data was published March 5, 2026 in Nature Communications. Researchers used a technique called radio occultation — beaming a radio signal from Mars Express to TGO as it disappeared over the Martian horizon, allowing scientists to probe atmospheric layers by how the signal bent.

"The results improve our understanding of Mars by revealing how solar storms deposit energy and particles into Mars's atmosphere," said Colin Wilson, ESA project scientist for Mars Express and TGO. "This is important as we know the planet has lost huge amounts of water and most of its atmosphere to space."

There's a practical angle too: a supercharged upper atmosphere can block radar signals used to explore the planet's surface — a key consideration for future missions.

This article synthesizes ESA's press release with verification against the peer-reviewed Nature Communications paper.

This article synthesizes ESA's official press release with verification against the peer-reviewed Nature Communications study. The reporting connects the data points from the paper with context from ESA scientists.