A solar outburst that occurred in 2021 was so powerful that it was felt on numerous Solar System worlds at the same time.
Even though the planets were on opposite sides of the Sun at the time, instruments on Earth, the Moon, and Mars all recorded intense solar activity for the first time.
It’s a collection of observations that can help us better understand solar activity and assess its possible impact on space development endeavors.
It is not unusual for the Sun to emit radiation and particles into space. It’s sort of the Sun’s entire schtick. Coronal mass ejections, in which the Sun ejects billions of tons of material and magnetic fields into the Solar System, are also not uncommon or particularly concerning.
Our atmosphere shields us from the full force of the Sun’s deadly radiation.
It’s a different story outside of the atmosphere. Space is considered a dangerous radiation environment, and astronauts who spend time in there may be more susceptible to radiation-related ailments. That’s merely the surrounding atmosphere.
A dose of the particle radiation from a particularly potent coronal mass ejection (CME) could result in radiation sickness at a level of roughly 700 millirays and, at a high enough intensity, around 10 gray, could be lethal within a week.
We’ve only been fortunate enough to see such levels so far, but CMEs are capable of producing them.
Crewed trips to the Moon and Mars, neither of which has an atmosphere strong enough to shield against solar radiation, are now being planned by space agencies. Consequently, it is crucial to be aware of a CME’s potential strength and range.
The Sun belched out a CME so potent that it was detected on Earth’s surface on October 28, 2021, providing us with a lot of valuable knowledge. That is incredibly unusual. Our capacity to measure it was much more uncommon.
The radiation influx was discovered by the ExoMars Trace Gas Orbiter of the European Space Agency, the Curiosity Mars rover of NASA, the Chang’e-4 Moon Lander of the Chinese National Space Administration, the Lunar Reconnaissance Orbiter of NASA, the Eu:CROPIS Earth orbiter of the German Aerospace Center, and ground-based neutron monitors on Earth.
At the time, Earth and Mars were on different sides of the Sun, spaced apart by about 250 million kilometers (155 million miles); Mars is, of course, further away from the Sun than Earth. As a result, the detections enabled researchers to examine how a CME’s material spreads and its consequences at various locations within the inner Solar System.
The radiation dose in orbit would have been 10 millirays on Earth, while the dose at the surface was insignificant. The Moon’s orbit was measured at 31 millimeters, while its surface was measured at 17 millimeters. On Mars, the orbital measurement was 9 milligray, and the surface measurement was 0.3 milligray.
Astronomer Jingnan Guo of the University of Science and Technology of China led the analysis. “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,” he says.
Future crewed trips to the Moon’s surface will be extremely dependent on our understanding of these events.
The good news is that we typically receive some advance notice before a CME emerges.
After a CME is launched, it takes between 15 and 18 hours to a few days for the particles to reach Earth and other planets.
Space explorers will be better prepared for battening down the hatches as a solar storm approaches if they are aware of how CMEs propagate and how violently they do so.
The research has been published in Geophysical Research Letters.