A crewed mission to Mars would expose astronauts to radiation levels higher than the safe limits set by space agencies, even with metal shielding, simulations have revealed.
There have been real-world and simulated studies of radiation doses in space, but these tend to be either time-limited or restricted in scope, such as only accounting for specific organs or focusing on men only.
鈥淢any calculations took a very simplistic approach, but we have done it in a more comprehensive way,鈥� says at New York University Abu Dhabi in the United Arab Emirates. 鈥淚 wanted to know exactly what these numbers are so that I could make up my own judgement whether such missions are safe or not.鈥�
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Atri and his colleagues bombarded virtual models of male and female bodies with cosmic radiation and solar bursts using software designed to let particle accelerators track how particles move through matter.
They then estimated radiation levels for more than 40 body parts and organs during a Mars mission with 600 days spent in space and 400 days on the Martian surface, with and without aluminium shielding in the spacecraft.
Many of the radiation levels for individual organs were found to be above 1 sievert, which is the safe cumulative dose for an astronaut鈥檚 career set by the European and Russian space agencies. NASA鈥檚 guidance says the total career radiation dose shouldn鈥檛 exceed 0.6 sieverts.
Atri and his team then looked at the pathological effects of similar or lower radiation doses in the real world, such as in nuclear accidents, radiotherapy and medical studies. They found that even lower doses than their estimates could cause memory problems in the brain, thyroid cancer and cardiovascular problems.
However, the results don鈥檛 account for differences in how individuals might respond to the same dose of radiation. 鈥淭hese doses are in a grey zone, which is about 1 sievert,鈥� says Atri. 鈥淪o it is certainly risky, and there will be a fraction of astronauts who are going to have a higher probability of getting cancer or maybe other diseases because of this, but maybe some will be fine.鈥�
Having this sort of data is important for any future space missions beyond Earth, says at the UK Space Agency. She adds that her agency and others are working on ways to mitigate radiation, such as building shelters under the Martian surface and more advanced shielding on spacecraft.
The dangers of space radiation might be even worse than Atri鈥檚 findings suggest, says at University College London. Cosmic radiation includes charged particles that are heavier than protons or helium. These aren鈥檛 accounted for in the analysis and the safe limits of them aren鈥檛 well understood.
The effects of these heavy charged particles on the body, for which we have limited concrete data, could be far more damaging than those of other radiation sources. 鈥淚t鈥檚 one thing for UV radiation getting a few point mutations, but it鈥檚 another when there鈥檚 a literal atom tearing through a chromosome and causing rearrangements or ionising everything in its path,鈥� says Siew.
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