Massive explosions from the sun pose a radioactive triple threat to the moon, Earth, and Mars

• An explosion from the sun blasted radiation into space, reaching the Earth, Mars, and the moon in 2021.
• These particles cannot harm humans on Earth, but they may harm people in space, research shows.

Sometimes the sun erupts, spewing high-energy particles across space, like a lactose-intolerant person heading to the bathroom after a glass of milk.

These are called coronal mass ejections, and a particularly intense one produced particles that hit Mars, Earth, and the moon in October of 2021.

It's the first time one of these events has been recorded on all three bodies, the European Space Agencies reported last week.

If there had been an astronaut up on the moon or Mars at the time these particles hit, they would've been exposed to radiation, though the levels were below a lethal dose. In 1972, however, a solar outburst delivered a high dose of radiation that could have threatened astronauts' health, but no astronauts were in space at the time, per Space.com.

As the sun begins entering a more active stage, CMEs will likely become more common and stronger, which means more radiation risk for astronauts.

These events are especially important to keep an eye on when considering that NASA intends to send people back to the moon as soon as 2025.

A more active sun means more coronal mass ejections and space radiation

There are two things that might explain why the particles from the October 2021 event went so far and wide, Robert Steenburgh, a space weather scientist at the National Oceanic and Atmospheric Administration, told Insider.

First, we've only been able to monitor activity on all three planets since 2016, and second, it was a particularly big ejection.

The reason the ejection was so large likely has to do with the stage of life the sun is in, Steenburgh said. It goes through a cycle of phases roughly every 11 years.

Right now it's in its active phase, where more sunspots begin blooming, like a pimply teenager.

During these active periods, it's common for space scientists to observe two or three eruptions a day on the sun's surface. In more dormant periods, there's an average of one per week, according to NASA.

We're likely going to hit solar maximum, when these events will be their most intense and frequent, in late 2024. After that, the sun will slowly return to a more dormant state, where some CME's still happen, but are less common.

Safe on Earth but not the moon

People on Earth don't have to worry about being radiated by these particles because Earth's magnetic field shields us from them Steenburgh said.

This field is like a "'quicker picker upper' for most of the particles. So that's why people on the ground you know, don't have to worry about this stuff," he said.

Astronauts in space or on the moon don't have this protection. Yet research in outer space continues.

So if astronauts are up on the moon at the wrong time, they may be exposed to life-threatening levels of radiation coming from an ejection. It could also be dangerous to be on Mars, though its sparse atmosphere does filter out some of the radiation, Space.com reported.

The spacesuits that astronauts wear may help up to a certain point, but if they're outside when particles from a CME hit, the suits wouldn't be enough, Steenburgh said.

That's why his team is in near constant communication with the Space Radiation Analysis group. They're a division of NASA that monitors how much radiation each person takes in during a space mission to determine if they've reached a level that is too dangerous for them to return again.

Steenburgh said parts of the International Space Station can be refuges from radiation. In the future, similar safeguards could be established on the moon and Mars.

So for now, the best response space authorities have is to monitor these events. Then, groups like Steenburgh's can alert governments to move their astronauts to safer areas.

"Our job is to help them understand when it's okay to be outside," he said.