Researchers put model predictions of radiation to the test ahead of future manned missions to Mars.
Cold, dry, airless – Mars doesn’t make the most comfortable environment for human exploration. But what makes a manned mission to the Red Planet truly dangerous is its radiation, which is thought to be more than 500 times more potent than here on Earth.
Now, a team based in Germany and the US has made an important step towards predicting when, where and with what strength this radiation will strike. Their work, which has just been published in Life Sciences in Space Research, compares theoretical predictions of different models with actual observations for the first time. This work could one day be used to mitigate the risk to Mars explorers of radiation sickness and cancer.
“Using different models and comparing them to available data allows us to better understand the weaknesses and strengths in those models, and how we can apply them to extend our knowledge beyond the measurements,” explains lead author Daniel Matthiä of the German Aerospace Center in Cologne. “We can use the models to determine hypothetical scenarios, for example, the radiation exposure in shelters, habitats and underground.”
Radiation on Mars is far from consistent. Most of it consists of cosmic rays – high-energy particles shooting from outer space – and these vary with the fluctuating strength of the Sun’s protective magnetic field. But just being able to forecast general levels of cosmic rays isn’t enough, as different high-energy particles have different effects on human physiology, and the geography of Mars means that some places are more exposed than others.
There is already a handful of computer models that can predict, in high detail, the changing radiation field on Mars generated by cosmic rays. However, it is not known how accurate these predictions are.
Matthiä and colleagues have begun to find out, by comparing model predictions with data taken from the Radiation Assessment Detector (RAD) instrument aboard NASA’s Curiosity rover on Mars since 2012. This effort was part of a “Blind Challenge” Model Comparison Workshop organized by Matthiä, Don Hassler at Southwest Reseach Institute in Boulder, Colorado (Principal Investigator of the RAD investigation) and the RAD team. The RAD is supported by NASA and DLR to make exactly these kind of measurements to help improve astronaut safety on future human missions to Mars. Building on a preliminary comparison last year, the researchers asked several modelling groups to predict the radiation environment on the surface of Mars for a two-month period, without seeing Curiosity’s results beforehand. “This is harder than it sounds,” says Matthiä.
Although the researchers are unable to quantify the accuracy of the model predictions yet, Matthiä says they were surprised in some cases by how much the models disagreed with each other and with the observational data. But this will help to improve the model predictions, he says, and ultimately provide more confidence when planning manned missions to Mars.
“Understanding, mitigating and managing the radiation environment for astronauts on a manned mission to Mars is a challenging, but not unsurmountable, problem,” Matthiä adds. “The more we understand about the environment, its variability, and its effect on humans, the safer our astronauts will be.”
Comparisons of model predictions and RAD data are not the only way to study the health effects of space radiation during a manned Mars mission, however. Last year, in another paper published in Life Sciences in Space Research, scientists reported upgrades at NASA’s Space Radiation Laboratory (NSRL) at the Brookhaven National Laboratory in Upton, New York, enabling the effects of cosmic rays to be simulated experimentally with greater precision here on Earth.
D. Matthiä et al.: “The radiation environment on the surface of Mars – Summary of model calculations and comparison to RAD data,” Life Sciences in Space Research (2017)