Attention Mars Explorers: Besides Low-Gravity, There’s Also Radiation

The director of astrobiology at Columbia University saw something this week that he just had to respond to: Elon Musk “talking about sending 1 million people to Mars by 2050, using no less than three Starship launches per day (with a stash of 1,000 of these massive spacecraft on call).” Iwastheone shared this article from Scientific American: The martian radiation environment is a problem for human explorers that cannot be overstated… For reasons unclear to me, this tends to get pushed aside compared to other questions to do with Mars’s atmosphere (akin to sitting 30km [18.6 miles] above Earth with no oxygen), temperatures, natural resources (water), nasty surface chemistry (perchlorates), and lower surface gravitational acceleration (1/3rd that on Earth). But we actually have rather good data on the radiation situation on Mars (and in transit to Mars) from the Radiation Assessment Detector (RAD) that has been riding along with the Curiosity rover since its launch from Earth. The bottom line is that the extremely thin atmosphere on Mars, and the absence of a strong global magnetic field, result in a complex and potent particle radiation environment. There are lower energy solar wind particles (like protons and helium nuclei) and much higher energy cosmic ray particles crashing into Mars all the time. The cosmic rays, for example, also generate substantial secondary radiation — crunching into martian regolith to a depth of several meters before hitting an atomic nucleus in the soil and producing gamma-rays and neutron radation… [I]f we consider just the dose on Mars, the rate of exposure averaged over one Earth year is just over 20 times that of the maximum allowed for a Department of Energy radiation worker in the US (based off of annual exposure)…. [Y]ou’d need to put a few meters of regolith above you, or live in some deep caves and lava tubes to dodge the worst of the radiation. And then there are risks not to do with cancer that we’re only just beginning to learn about. Specifically, there is evidence that neurological function is particularly sensitive to radiation exposure, and there is the question of our essential microbiome and how it copes with long-term, persistent radiation damage. Finally, as Hassler et al. discuss, the “flavor” (for want of a better word) of the radiation environment on Mars is simply unlike that on Earth, not just measured by extremes but by its make up, comprising different components than on Earth’s surface. To put all of this another way: in the worst case scenario (which may or may not be a realistic extrapolation) there’s a chance you’d end up dead or stupid on Mars. Or both.