Question: I have been watching a programme on the television about the preparations for a manned mission to Mars. As Mars has a very thin atmosphere the men who land on the planet will be subjected to “solar radiation”. How dangerous will this radiation be to the astronauts and will it restrict the amount of time that they can actually spend exploring the Martian surface? — David
Answer: In fact, this question has been analyzed quite extensively by David Chappell in his article on Radiation and the Human Mars Mission. This analysis results in two estimates that differ by a factor of about 25, so this is a rather difficult thing to quantify. What this study does conclude, though, is that measures will be need to shield astronauts from radiation exposure both while in-transit to Mars and when they arrive. Actual measurements of the Mars surface radiation environment are currently being made by the RAD (Radiation Assessment Detector) on board the Curiosity rover. These measurements will provide a clearer picture as to what measures need to be taken to allow astronauts to travel to and work on Mars.