Sending humans to Mars requires scientists and engineers to overcome a series of technological and safety challenges. One of these challenges is the serious risk posed by radiation from the sun, distant stars, and galaxies.
Answering two crucial questions will help overcome this barrier: Does radiation pose a significant threat to human life during the journey around the Red Planet? And can the timing of the mission to Mars help protect astronauts and spacecraft from radiation?
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The optimal timing to send humans to Mars is when the sun reaches its maximum activity. Image: NASA.
In a recent paper published in the journal Space Weather, an international team of space scientists, including researchers from the University of California, Los Angeles (UCLA), answered those questions with a “no” and a “yes,” respectively.
This means that humans can safely travel to and from Mars, provided that spacecraft have sufficient shielding and the round trip takes less than approximately 4 years. Moreover, the timing of the human mission to Mars does make a difference. Scientists have determined that the best time for departure from Earth is during the solar maximum, the period of heightened solar activity.
Calculations by the scientists have shown that during this time, spacecraft on Mars can be shielded from the energetic particles emanating from the sun because, during the solar maximum, the most hazardous and energetic particles from distant galaxies are deflected due to the enhanced solar activity. According to Yuri Shprits, a geophysics researcher at UCLA and the author of the study, the average journey to Mars takes about 9 months, so depending on the launch window and available resources, a manned mission can reach Mars and return to Earth in less than 2 years.
“This study demonstrates that while space radiation poses stringent limits on spacecraft weight and launch duration, and presents technological challenges for human missions to Mars, such a mission is feasible,” said Shprits, who is also affiliated with the GFZ German Research Centre for Geosciences in Potsdam, Germany, where he is responsible for space weather and space physics.
The researchers proposed a mission duration of no more than 4 years, as a longer journey would expose astronauts to high levels of dangerous radiation during the round trip, even assuming they depart during a relatively safe period. They also reported that the primary danger for such a flight would be particles from beyond our solar system.
Shprits and his colleagues from UCLA, MIT, Skolkovo Institute of Science and Technology in Moscow, and GFZ Potsdam combined models of particle radiation for a solar cycle with models of how radiation would affect humans, including different impacts on different organs and the spacecraft.
The models determined that a relatively thick spacecraft hull can help protect astronauts from radiation, but if the shielding layer is too thick, it can actually increase the amount of secondary radiation they are exposed to.
The two main types of hazardous radiation in space are solar energetic particles and galactic cosmic rays, with the intensity of each type depending on solar activity.
Galactic cosmic rays have their minimum activity level within 6 to 12 months after the solar maximum, while the intensity of solar energetic particles is highest during the solar maximum.