NASA has set its sights on the Moon, aiming to send astronauts to the lunar surface by 2026 and establish a long-term presence by 2030. However, the Moon isn’t exactly a habitable place for humans.
Cosmic rays from distant stars and galaxies and solar energetic particles from the Sun bombard the lunar surface. Exposure to these particles can pose a risk to human health. Both galactic cosmic rays and solar energetic particles are high-energy particles that travel at nearly the speed of light. While galactic cosmic radiation arrives at the Moon in a relatively constant stream, energetic particles can come from the Sun in large bursts, penetrating the human body and increasing the risk of cancer.
The Earth has a magnetic field that acts as a shield against high-energy particles from space. The Moon, however, does not have a magnetic field, making its surface vulnerable to this bombardment of particles. During a large solar energetic particle event, the radiation dose an astronaut receives inside a spacesuit could exceed that received by a person on Earth by 1,000 times, exceeding the recommended lifetime exposure limit by ten times. of an astronaut.
The challenge of the Artemis program
NASA’s Artemis program, which began in 2017, aims to re-establish a human presence on the Moon for the first time since 1972. Lulu Zhaofrom the University of Michigan, outlined probable solutions:
My colleagues and I at the University of Michigan’s CLEAR center, the Center for All-Clear SEP Forecast, are working to predict these particle ejections from the Sun. Predicting these events could help protect future Artemis crew members.
The Moon is facing dangerous levels of radiation in 2024, as the Sun approaches the maximum point of its 11-year solar cycle. This cycle is driven by the Sun’s magnetic field, whose total strength changes dramatically every 11 years. As the Sun approaches its maximum activity, up to 20 large solar energetic particle events can occur each year. Both solar flares, which are sudden bursts of electromagnetic radiation from the Sun, and coronal mass ejections, which are expulsions of large amounts of matter and magnetic fields from the Sun, can produce energetic particles.
The Sun will reach its solar maximum in 2026, the expected launch point for the Artemis III mission, which will carry a crew of astronauts to the lunar surface. Although researchers can follow the Sun’s cycle and predict trends, it is difficult to guess when exactly each solar energetic particle event will occur and how intense each event will be. Future astronauts on the Moon will need a warning system that predicts these events more accurately before they happen.
Predict solar events
In 2023, NASA funded a five-year space weather center of excellence called CLEAR, with the goal of predicting the probability and intensity of solar energetic particle events. Currently, forecasters at the National Oceanic and Atmospheric Administration Space Weather Prediction Center, the center that monitors solar events, cannot issue a warning for an incoming solar energetic particle event until they actually detect a solar flare or mass ejection coronal.
These events are detected by observing the Sun’s atmosphere and measuring the X-rays coming from the Sun. Once a forecaster detects a solar flare or coronal mass ejection, the high-energy particles arrive at Earth in less than an hour. Now. But astronauts on the lunar surface would need more time to find shelter.
The solar magnetic field is incredibly complex and can change throughout the solar cycle. While scientists don’t fully understand what causes these solar events, they do know that the Sun’s magnetic field is a major trigger. In particular, they are studying the strength and complexity of the magnetic field in certain regions of the solar surface, as explained by Zhao:
My team at CLEAR wants to predict solar flares and coronal mass ejections before they happen. At the CLEAR center, we will monitor the Sun’s magnetic field using measurements from telescopes both on the ground and in space, and build machine learning models to predict solar events, hopefully more than 24 hours in advance.
With the forecasting framework developed at CLEAR, we also hope to predict when the particle flux will return to safe levels. In this way, we will be able to inform astronauts when it is safe to exit their shelter and continue their work on the lunar surface.
