To send humans to Mars, scientists and engineers would have to overcome a number of technological and safety challenges. The extreme danger presented by particle radiation from the sun, distant stars, and galaxies is one of them.
Answering two crucial questions would go a long way toward helping you get over that stumbling block: Would particle radiation represent a significant threat to human life on a round trip to Mars? Could the timing of a Mars mission help to shelter astronauts and the spacecraft from radiation?
An international team of space scientists, including UCLA researchers, responds to those two questions with a “no” and a “yes” in a new report published in the peer-reviewed journal Space Weather.
That is, humans should be able to travel to and from Mars safely, providing the spaceship has adequate shielding and the round trip is less than four years. The scientists found that the optimal moment for a journey to depart Earth would be when solar activity is at its greatest, known as the solar maximum.
Because the most harmful and energetic particles from distant galaxies are deflected by increased solar activity at solar maximum, the scientists’ calculations show that a Mars-bound spacecraft may be shielded from energetic particles from the sun.
A journey of that length is feasible. According to Yuri Shprits, a UCLA research geophysicist and co-author of the report, the usual voyage to Mars takes around nine months, so depending on the schedule of launch and available fuel, a human mission may reach the planet and return to Earth in less than two years.
“While space radiation places strict limits on how heavy a spacecraft can be and when it can launch, and it poses technological challenges for human missions to Mars,” said Shprits, who is also the head of space physics and space weather at the GFZ Research Centre for Geosciences in Potsdam, Germany.
The researchers advocate a mission of no more than four years since a lengthier travel would expose astronauts to dangerously high levels of radiation on the round trip, even if they went when radiation levels were lower. They also claim that particles from beyond our solar system would pose the greatest threat to such a voyage.
Shprits and colleagues from UCLA, MIT, Moscow’s Skolkovo Institute of Science and Technology, and GFZ Potsdam coupled geophysical models of particle radiation during a solar cycle with estimates of how radiation would damage both human passengers and a spaceship. According to the modeling, a spacecraft’s shell made of a relatively thick material can help shield humans from radiation, but if the shielding is too thick, it can actually increase the quantity of secondary radiation to which they are exposed.
Solar energetic particles and galactic cosmic rays are the two main types of harmful radiation in space, and their intensity varies depending on solar activity. According to Shprits, galactic cosmic ray activity is lowest six to twelve months after the height of solar activity, whereas the intensity of solar energetic particles is highest at solar maximum.