Science Alert  August 7, 2023 On 28 October 2021, solar eruptions caused intense and long-lasting solar energetic particle (SEP) flux enhancements observed by spacecraft located over a wide longitudinal range in the heliosphere. SEPs arriving at Earth caused the 73rd ground level enhancement (GLE) event recorded by ground-based neutron monitors. This is also the first GLE event seen on the surface of three planetary bodies, Earth, Moon, and Mars, by particle and radiation detectors as shown in this study. An international team of researchers (China, Germany, Bulgaria, USA – Southwest Research Institute, Boulder, CO, industry, University of New Hampshire) derived […]