By comparison, during the event on 28 October 2021 the dose in lunar orbit, measured by NASA’s Lunar Reconnaissance Orbiter, was only 31 milligray. “Our calculations of the past ground level enhancement events show that on average one event every 5.5 years may have exceeded the safe dose level on the Moon if no radiation protection had been provided. Understanding these events is crucial for future crewed missions to the surface of the Moon,” says scientist Jingnan Guo who researched the 28 October event.

When we compare the measurements made by ExoMars TGO and by the Curiosity rover, the protection offered by Mars’s atmosphere becomes clear: TGO measured 9 milligray, 30 times more than the 0.3 milligray detected on the surface.

ESA’s inner Solar System missions Solar Orbiter, SOHO and BepiColombo were also caught in the blast of the outburst, providing even more vantage points to study this solar event.

“Currently, we live in a golden age of Solar System physics. Radiation detectors aboard planetary missions such as BepiColombo, on its way to Mercury, and Juice, cruising to Jupiter, add a much-needed coverage to study the acceleration and propagation of solar energetic particles,” remarks Marco Pinto, ESA research fellow working on radiation detectors.