The Artemis II astronauts are about to take off on a record-breaking flight around the moon, giving NASA a rare opportunity to study how deep space flight affects the human body.
After leaving Earth’s protective magnetic field, the four-person crew will be exposed to space weather, including bursts of high-energy radiation from the Sun known as solar flares.
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Live Science spoke with Patricia Leaf, a professor of physics and astronomy at Rice University in Houston, Texas, to discuss space weather and how it could affect the Artemis II mission.
Leaf has more than 50 years of experience researching space plasma physics and earned his PhD analyzing data from NASA’s first moon trip during the Apollo era. Here’s what she said about the radiation risks the Artemis II crew will be exposed to during their historic return to the moon:
Patrick Pester: What is space weather? How can it affect the health of astronauts?
Patricia Leaf: There are several types of space weather. Solar flares can release highly energetic particles that travel at near the speed of light and are energetic enough to penetrate the hull of a spacecraft, potentially harming astronauts on their way to the moon.
The long-term form of space weather is the result of coronal mass ejections (CMEs). When it hits Earth, it creates a beautiful aurora borealis. Although CME can affect power lines, it does not affect astronauts because it is low energy and poses no direct harm.
PP: Which is the most dangerous radiation source to which astronauts are exposed?
PR: There are two types of radiation that affect astronauts outside of Earth’s orbit. One is solar energy particles. These occur as a result of solar flares. They can be very intense, but are usually relatively short-lived. If such a storm occurs, astronauts will know where to go in the safest capsule.
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It’s like getting a chest X-ray every day. You don’t want to do it for too long.
patricia leaf
Another type of radiation dangerous to astronauts in deep space is galactic cosmic rays. They are much more energetic, but there are much fewer of them and they are always in the background. It’s like getting a chest X-ray every day. You don’t want to do it for too long. They are very energetic, so if they hit a spaceship, they are very difficult to defend against. [secondary rays] That could end up being almost as bad as the primary.
One good thing about the solar maximum we’re currently in is that the solar wind becomes stronger, which helps prevent galactic cosmic rays from penetrating the inner solar system. Therefore, if I were to go on a long-term mission to the Moon or Mars, I would definitely go during solar maximum rather than solar minimum.
PP: That’s interesting. Because I think it would be the opposite if the sun became more active.
PR: When the solar winds are strong, the sun can help drive us out of our neck of the woods, but we do have to worry about these individual events due to solar flares. And they come at the speed of light, so you don’t get much warning. Look on the sun and it’s here. On the other hand, they only last for a few hours, so even if you don’t get much advance warning, you can still protect yourself by hiding in a solid place.
One of the things they did for Artemis I was to attach sensors to different parts of the Orion spacecraft to find out where the safest place was. When I was working on the Apollo program, the first paper I published was on the solar flare that occurred in August 1972. The flare was so intense that if the astronauts had been on the Command Module Lunar Module, they would have received a near-lethal dose. [Fortunately, no astronauts were in space at the time.] So this is something we have to be careful about, and the good thing about the Orion spacecraft is that it has much better shielding than the original Apollo spacecraft.
PP: A recent study found that superflares are more likely to occur during solar maximum, and the lead author recommends that NASA postpone Artemis II until the end of the year. Are they right or wrong?
PR: The Sun has an 11-year cycle, and the largest flares generally occur when there are the highest number of sunspots. However, not all sunspot cycles are the same. The current sunspot cycle is stronger than the sunspot cycle of 11 years ago, but weaker than other sunspot cycles. So we don’t necessarily think there’s any extra risk of superflares now than there was 20 years ago.
That said, it’s still possible. That’s why we keep our eyes on the sun. We observe these sunspot groups and study the structure of the Sun’s magnetic field. When a magnetic field’s structure becomes highly tangled or twisted, energy accumulates within it, much like winding up a rubber band on a paper airplane. And when a solar flare occurs, that energy is released. That’s the energy that causes massive solar flares.
PP: One of Artemis II’s mission goals is to study the effects of space radiation on the health of astronauts. How do we do that?
PR: All astronauts wear monitors to measure how much radiation they absorb. And there is both an annual maximum and a lifetime maximum. In other words, once an astronaut receives the maximum amount of radiation in their lifetime, that’s it. They retire from going to space. Interestingly, the maximum permissible lifetime dose for an astronaut is higher than the maximum permissible lifetime dose for an airplane pilot, because it is a much more dangerous job by its nature, and pilots contract to do so because of the risks involved.
Editor’s note: This interview has been edited and condensed for clarity.
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