The idea of sending humans on a mission to Mars seemed distant or science fiction at one point. The day humans will travel to Mars is quickly approaching, with numerous space agencies and commercial space companies looking to mount missions over the next decade. There are many technical and human issues that must be addressed before this can occur.
There are always questions about radiation mitigation in any discussion of crewed missions on Mars. A new international study by space scientists examined the question of whether radiation from particle radiation is too dangerous and how radiation can be mitigated through careful timing. They concluded that a mission to Mars was possible, but could not last more than four years.
Mikhail Dobynde was the researcher at the Skolkovo Institute of Science and Technology and Russian Academy of Science and in Moscow. He was joined by members of the GFZ German Research Centre for Geosciences (Helmholtz Centre Potsdam, Germany), the University of California Los Angeles (UCLA) and the Massachusetts Institute of Technology(MIT).
The team considered the radiation threat posed to them by two types of radiation sources for the purpose of their study: Solar Energetic Particles, (SEP), and Galactic Cosmic Rays, (GCR). The first includes fast-moving protons and electrons. They can also negatively impact electronics and living tissue. These particles are also energetic but come from beyond the Solar System. They are often attributed to supernovas.
Both of these radiation sources are affected by the level of solar activity. SEP levels are lowest during a solar maximum, while GCR activity is highest. GCR activity is at its lowest, while SEP is highest during solar maximum. The team used geophysical models to assess the danger posed by these sources. They also considered how the radiation levels during the 11-year solar cycles.
These models were then combined with models of radiation's effects on human passengers (including various bodily organs) as well as their spacecraft. Next, the team ran Monte-Carlo simulations to simulate radiation propagation. This included 10 types of SEP radiation as well as 28 types fully-ionized GCR element elements. They concluded that Mars would be best served during the six to twelve month period after the peak of solar activity (aka. solar maximum).
GCR activity reaches its lowest point at this point and SEP starts to decline from its highest intensity. Over the next six-and-a-half years, the situation reverses with GCR activity gradually increasing until it reaches maximum intensity. This coincides with a solar minima. A crewed return mission to Mars could be completed in less than two years, considering that Mars' average flight time is nine months.
NASA's Orion spacecraft will take astronauts farther into space than any other spacecraft using a module that is based on Europe's Automated Transfer Vehicles. NASA. Credit:
Dobynde and colleagues concluded that this would make sure that the mission reached home before the radiation environment becomes too dangerous. A mission lasting more than four years would be too long, as they would have to return home with higher levels of GCR activity. Their modeling also showed that spacecraft shielding would have to be thick in order to protect the crew's health.
These same results showed that shielding too thick could actually increase exposure to secondary radiation. This is where high-energy particles collide and shielding creates secondary particles. The International Space Station (ISS) has extensively studied this phenomenon, also known as a particle shower.
These results may prove to be very useful to future mission planners according to Yuri Shprits of GFZ Research Centre for Geosciences. He said that although space radiation has strict limits on the size and time of a spacecraft and presents technical difficulties for human missions, it is feasible.
This is important because there are many plans to continue regular missions to Mars in near future. These include NASA's Moon to Mars mission architecture and China's plans to send astronauts to Mars by 2033. Elon Musks plans to send payloads and crew to Mars every two years via the SpaceX Starship or Super Heavy launch vehicles.
Artist's impression of Mars Base Camp orbiting around Mars. Space radiation will pose the greatest risk to missions to Mars. Credit: Lockheed Martin
These are only a few visions of Martian exploration and settlement that have been presented recently. Mars is once more in the public's mind, with all the robotic missions that are currently exploring it and the possibility for human exploration. Mars is now being regarded as the next big leap in space exploration since the Apollo era.
Scientists, mission planners and astronauts have all found inspiration in Mars' status as the most habitable celestial body. Although it would be difficult to travel there, there are many people who are willing to take a trip. The prospect of Mars becoming the next frontier is a dream for these brave souls.
It is exciting to see these wild ideas come to life when they are supported by realistic assessments. Great things can be achieved when science and romance are combined to plan for the future.
Additional Reading: UCLA, Space Weather
