Once upon a time, the idea of sending people to Mars seemed either a distant view or something out of science fiction. But with several space agencies and even commercial space companies planning missions in the next decade, the day humans will fly to Mars is fast approaching the point of realization. Before this can happen, several problems must first be resolved, including a variety of technical and human factors.
In any discussion about manned missions to Mars, there is always the question of whether or not we can mitigate the radiation threat. In a new study, an international team of space scientists looked at the question of whether particle radiation would be too great a threat and whether the radiation could be mitigated through careful timing. In the end, they found that a mission to Mars is feasible, but must not exceed four years.
The research was led by Mikhail Dobynde, a researcher from the Skolkovo Institute of Science and Technology and the Russian Academy of Sciences in Moscow. There were also members of the GFZ German Research Center for Geosciences at the Helmholtz Center Potsdam, the University of California Los Angeles (UCLA) and the Massachusetts Institute of Technology (MIT).
For their study, the team looked at the threat posed by the two main types of radiation sources: Solar Energetic Particles (SEP) and Galactic Cosmic Rays (GCR). The former consists of fast-moving protons, electrons and high-energy atomic nuclei that can have a negative effect on electronics and living tissue. The latter consist of the same series of high-energy particles, but come from outside the solar system and are attributed to supernovae.
The intensity of these two radiation sources depends on solar activity, with the SEP values being the least intense during a solar minimum, but the GCR activity being the most increased. The opposite is also the case where GCR activity is lowest during solar maximum but SEP is elevated. To assess the threat posed by these sources, the team combined geophysical models that examined how particle radiation changes during the 11-year solar cycle.
These were combined with models of how the radiation affects human passengers (including various body organs) and their spacecraft. The team then ran a series of Monte Carlo simulations of radiation propagation that took into account 10 different types of SEP radiation and 28 types of fully ionized GCR elements. From this they determined that the best time for a mission on Mars is in the six to twelve months after the solar activity peaks (also known as the solar maximum).
At this point GCR activity is lowest and SEP begins to decrease from its highest intensity. The situation is slowly reversed over the next six and a half years, with GCR activity slowly increasing until it reaches its maximum intensity (which coincides with a solar minimum). Since the average flight time to Mars is around nine months, a manned return to Mars could be accomplished in less than two years.
NASA’s Orion spacecraft will propel astronauts further into space than ever before with a module based on Europe’s Automated Transfer Vehicles (ATV). Photo credit: NASA
Based on their findings, Dobynde and his colleagues determined that this would make the mission home before the radiation environment became too dangerous. But a mission that lasted up to four years would move them forward as they would be forced to return home amid higher GCR activity. Therefore, their modeling also showed that the spacecraft’s shielding would have to be relatively thick to ensure the health of the crew.
However, the same results also indicated that too thick a shield could actually increase the amount of secondary radiation to which the crew is exposed. This phenomenon, in which high-energy particles collide with the shield to create a cascade of secondary particles (also known as “particle showers”), has been studied in depth on board the International Space Station (ISS).
According to Yuri Shprits, head of space physics and space weather at GFZ’s Geosciences Research Center (and co-author of the paper), these results could be of great value to future mission planners. “This study shows that while space radiation imposes severe restrictions on the severity of the spacecraft and time of launch, and poses technological difficulties for manned missions to Mars, such a mission is feasible,” he said.
These considerations are vital as there are several plans to undertake regular missions to Mars in the near future. These include NASA and its moon-to-Mars mission architecture, China’s plans to send crews to Mars by 2033 (and set up a permanent research outpost there), and Elon Musk’s plan to bring payloads and crew members every two years with the SpaceX Starship and the Super heavy start to deploy vehicle.
Artist’s impression of Mars Base Camp in orbit around Mars. When missions to Mars begin, one of the biggest risks will be space radiation. Photo credit: Lockheed Martin
These are just a few of the visions for the exploration (and colonization of Mars) that have been articulated lately. With all of the robotic missions currently exploring the planet and the possibility of human exploration on the horizon, Mars is reappearing in the public eye. Since the Apollo era, Mars has been considered the “next big leap” that could lead to a new era, a revived space age!
The fact that Mars is the most habitable celestial body beyond Earth has also been a source of inspiration for scientists, mission planners, astronauts and futurologists alike. Despite the challenges getting there, there is currently no shortage of people willing to sign up for a one-way trip. For these adventurous souls, the prospect of the first groundbreaking on Mars – the next big “frontier” – has a certain romance.
It is particularly exciting, however, when realistic assessments show that these adventurous ideas can actually be implemented with the right preparations, technologies and mitigation strategies. When scientific facts and romance come together to make plans for the future, great things can happen!
Further reading: UCLA, Space Weather