A grand coronal mass ejection from the sun sent a barrage of energetic particles hurtling towards the Earth, moon and Mars on October 28, 2021, it was recently confirmed by scientists.
The rare 'ground level enhancement' caused particles to breach Earth's magnetic bubble, impacting all three celestial bodies simultaneously - a phenomenon never-before witnessed.
International spacecraft, including ESA's ExoMars Trace Gas Orbiter (TGO), NASA's Curiosity Mars rover, CNSA's Chang'e-4 Moon lander, and NASA's Lunar Reconnaissance Orbiter (LRO) detected the cosmic onslaught.
"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," stated Marco Pinto, ESA research fellow working on radiation detectors.
The lack of magnetic fields on the moon and Mars makes them vulnerable to direct solar particle interactions. Mars, however, enjoys some protection from its thin atmosphere, slowing down the most energetic particles. Understanding these solar events is crucial for future human missions to these worlds as astronauts face the risk of radiation sickness, with lethal doses exceeding 10 gray.
Comparing the measurements from the different spacecraft, it becomes evident that Mars' atmosphere is beneficial in reducing radiation exposure. TGO recorded 9 milligray, whereas the Curiosity rover measured a dose of 0.3 milligray on the Martian surface.
The dose above 10 gray, if applied to an astronaut, is considered extremely dangerous as it might destroy bone marrow.
ESA's inner Solar System missions, Solar Orbiter, SOHO, and BepiColombo, were also caught in the solar blast, expanding the scope for studying such events. The ongoing Artemis program, aiming to send astronauts to the moon, includes the lunar orbiting Gateway space station equipped with instruments to monitor radiation and protect future explorers.
To further safeguard astronauts, space agencies are investigating protective attire, as demonstrated by two mannequins aboard the Artemis I test flight. Researchers are comparing the data collected from "Helga," who flew unprotected, and "Zohar," wearing a newly-developed radiation protection vest.
The findings regarding this peculiar event was published in Geographical Research Letters journal.