Data returned by the ESA-Roscosmos ExoMars Trace Gas Orbiter indicates that astronauts on even short future Mars missions could face significant space radiation hazards. The readings from the orbiter show that even on a flyby mission to Mars with no landing or orbiting, a crew would be exposed to at least 60 percent of their total lifetime career radiation exposure limit.
Even before the first rocket left the Earth's atmosphere in the 1940s, space medicine pioneers recognized that cosmic radiation would be a real danger to future space travelers. Today, after over 75 years of popping things into the beyond, we have a much better understanding of the hazard radiation poses to any potential deep space missions.
Though the Trace Gas Orbiter has only been studying Mars since April of this year, it's been measuring space radiation ever since its launch in 2016. As with other deep space probes, the Orbiter kept track of the radiation in its vicinity using special instruments. In this case, it was the Liulin-MO dosimeter of the Fine Resolution Epithermal Neutron Detector (FREND), which measures the neutron fluxes coming from Mars in high spatial resolution as well as the flux, absorbed dose, and dose intensity from cosmic rays.
The Orbiter has confirmed that the radiation exposure to astronauts on a Mars mission would be a high one. On Earth, the atmosphere and the magnetic field protect us from the cosmic rays that constantly bombard us from space. Even on the International Space Station (ISS) the astronauts are protected by that same field, though to a lesser extent.
However, away from the Earth, things are very different. Though the Sun's magnetic field and the solar winds can provide some protection, at times of low solar activity the radiation exposure can be very high, and even during these periods there's the threat of radiation from solar storms and flares. If the radiation exposure is severe enough, the crews on an interplanetary mission can face radiation sickness, greater risk of cancer, suppressed immune systems, degenerative diseases, and even the central nervous system can be affected.
According to the Orbiter measurements, astronauts on a quick there-and-back-again mission to Mars with no stopovers would be in space for a year, during which time they'd be exposed to 600 mSv for the round-trip. To put that into perspective, the average person on Earth would only receive two mSv per year or about the equivalent of two chest X-rays. This corresponds to earlier measurements by NASA's Mars Science Laboratory taken on its journey to Mars in 2011 to 2012.
"One of the basic factors in planning and designing a long-duration crewed mission to Mars is consideration of the radiation risk," says Jordanka Semkova of the Bulgarian Academy of Sciences and lead scientist of the Liulin-MO instrument. "Radiation doses accumulated by astronauts in interplanetary space would be several hundred times larger than the doses accumulated by humans over the same time period on Earth, and several times larger than the doses of astronauts and cosmonauts working on the International Space Station. Our results show that the journey itself would provide very significant exposure for the astronauts to radiation."
The results were presented at the European Planetary Science Congress (EPSC) in Berlin.
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