Currently, astronauts get some radiation protection from their spacecraft and from equipment such as spacesuits.
But many new shielding plans designed for interplanetary flight are on the drawing board, including one that would use drinking water and wastewater to create an insulated safe haven within the spacecraft.
Still, only advance warning of severe events would give astronauts time to retreat into protected "cocoon" areasand to ensure that no one is caught unprotected on a spacewalk or on the Martian surface.
"The probability is that [astronauts] would be subjected to one or more major solar events," Colorado's Baker said. "You could possibly avoid them, but if you travel for months to Mars, spend time on the surface, and then travel for months on the return, the probabilities become rather high."
"You can be shielded in the spacecraft, but if you need to go out and have extravehicular activities, you need some forecasting," the University of Warwick's Foullon added. "You never know when you'll need to go out."
Forecasting in the Void
To forecast accurately for a Mars mission, Foullon recommends a pre-mission launch of three satellites designed to provide space weather alerts. She also advocates the design of a lightweight warning device to be carried aboard the spacecraft.
Space weather forecasters need tools like these to monitor solar events, she says.
"We have satellites that look at the sun, so we have an understanding of what's going on, even if it's not perfect," Foullon said. "There are warning stations dedicated to looking at the risks for spacewalks or extravehicular activities."
It helps that solar events occur on an 11-year cycle, which assists forecasters in predicting periods of high activity. Space's great distances help with projections, too, because solar particles and magnetic fields take several days to reach Earth.
"Modeling efforts begin below the solar surface and model the propagation of energy from the sun to the Earth with the idea of understanding, and eventually predicting, the chain of cause and effect all the way from the sun to the [Earth's] lower atmosphere," said Patricia Reiff, director of the Rice Space Institute at Rice University in Houston.
But a Mars mission would enter vast reaches of more distant space where the impact of such events is not fully understood.
"If the challenge is to go to Mars, that is making us progress in our knowledge," Foullon said.
Space Weather On Earth
Our planet's magnetic field usually protects Earth from solar events. However, particles do reach Earth, and we occasionally experience their effects.
When blasts of solar particles arrive at the poles they can produce aurora borealisthe Northern Lights.
Other effects are far less pleasant. Particle streams can cause magnetic storms that damage satellite and radio communications, impair navigation systems, and in extreme cases even cause electrical blackouts.
"A friend teaches space weather to cadets at the [U.S] Air Force Academy," Rice's Reiff reported. "The cadets were doing a GPS mapping exercise during a space weather storm, and the ionosphere was in such a turbulent state that their mapping accuracies went from a few meters before the storm to nearly a hundred meters during the storm, all because of space weatherthat could be tragic."
Commercial airlines even avoid polar routes, where radiation exposure is higher, during solar storms.
But some experts caution that more research is needed to understand just how such radiation affects human health.
"There is a lot that goes on between measuring a certain input outside the spacecraft and measuring how that actually impacts the human body," Colorado's Baker said.
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