Manned Mars mission viable if it doesn't exceed four years, concludes international research team

Yuri Shprits from UCLA, a research geophysicist, stated that limiting the round trip to Mars would reduce radiation exposure. Credit: NASA
To send human beings to Mars, engineers and scientists must overcome many technological and safety hurdles. One of these is the serious risk posed to human life by radiation from distant stars, the sun and galaxies.

Two key questions could help overcome that obstacle: Does particle radiation pose too serious a threat to human health during a round trip around the red planet? Could the timing of a mission on Mars be a factor in shielding astronauts and spacecraft from radiation?

A new article in Space Weather is published by a peer-reviewed team of scientists from around the world, which answers these two questions with "no" or "yes".

This means that humans should be able safely travel to Mars provided the spacecraft is equipped with sufficient shielding and the trip takes less than four years. It would also make a big difference when a human mission to Mars is launched. Scientists determined that the peak solar activity, or the solar maximum, would be the best time to fly to Mars.

Scientists have calculated that it is possible to shield a Mars-bound spacecraft against energetic particles from solar radiation. This is because during solar maximum, most of the most energetic and dangerous particles from distant galaxies can be deflected.

It is possible to make a trip this long. According to Yuri Shprits (a UCLA geophysicist and coauthor of the paper), the average flight to Mars takes nine months. It is possible that a human mission could reach Mars and return to Earth in under two years depending on launch timing and fuel availability.

"This study shows, while space radiation imposes strict limits on the weight of the spacecraft and the launch time, and it presents technological problems for human missions to Mars," Shprits said. Shprits is also head of space physics at GFZ Research Centre For Geosciences in Potsdam.

Researchers recommend that a mission should not last more than four years. This is because astronauts would be exposed to dangerously high levels of radiation over the course of the round trip, even if they traveled when it was safer. The main threat to such a flight is from particles outside our solar system, according to the researchers.

Shprits and his colleagues at UCLA, MIT and Moscow's Skolkovo Institute of Science and Technology combined geophysical models of solar radiation with models of how radiation would affect human passengers, including its effects on different organs and a spacecraft. It was determined that astronauts could be protected from radiation by having their spacecraft's shell made of thick materials. However, too thick shielding could increase their exposure to secondary radiation.

Galactic cosmic rays and solar energetic particles are the two main forms of space-based radiation that can cause serious health problems. The intensity of each type of radiation depends on solar activity. According to Shprits, galactic cosmic ray activity drops between six and twelve months after peak solar activity. Solar energetic particles are at their highest intensity during solar maximum.

Further exploration of Mars-directed coronal masses ejections erupts from sun

M.I. Dobynde and colleagues, Beat 1 Sievert: Optimal radiation shielding of astronauts on a mission to Mars, Space Weather (2021). M.I. M.I. DOI: 10.1029/2021SW002749