Free Astronomy Magazine September-October 2019

48 SEPTEMBER-OCTOBER 2019 ASTRONAUTICS we cannot pre- dict the intrave- hicular radiation spectrum. This scenario further compli- cates the work of researchers engaged in mod- elling space ra- diation risk. It can indeed be guessed how the radiation environment of a space flight is unique, complex and unrepeat- able in the labo- ratory. It is the combination of some properties of the particles, such as charge, mass and en- ergy, that de- termine how quickly they lose energy by inter- acting with mat- ter. In the human body, the dam- age that a given organ receives depends not only on the en- ergy spectrum of the charged particles but also on the depth and density of the tissue mass that lies between the skin surface and the tar- get organ. In general, the heavier the charged particle, the greater the amount of energy deposited per unit path length for that particle. This relationship is re- ferred to as “linear energy transfer” (LET). The high-LET radiation found in the GCR spectrum can produce excessive free radi- cals that instigate oxidative damage to cell structures. Chronic exposure to such oxida- tive stress can lead to premature aging, car- diovascular disease and cataract formation. he schematic representa- tion on the left and the video above show the main effects that space radiation can have on the human body dur- ing a mission to Mars. [NASA] The precociousness of cataracts in some as- tronauts is currently the clearest evidence of what is involved in a long stay in space. Although the worst consequences are yet to be demonstrated, the remarkable ioniz- ing power of GCRs makes it a potentially significant contributor to tissue damage, carcinoma onset, central nervous system degeneration and other deleterious pathologies. More worrisome than GCRs on the effec- tiveness of the crews in the short term are the so-called “solar particle events” (SPE), which originate from the breaking of lines of force of active regions’ magnetic fields present at the surface of the Sun. These real explosions hurl into space short-lasting but very intense flows of ionizing radia- tion, which, if absorbed by the body of an astronaut in relevant doses, can cause nau- sea, vomiting, fatigue, weakness, respira- tory and digestive diseases, as well as damage to microcirculation. While these effects are mostly latent and do not neces- sarily entail an immediate risk to the crew’s health, they are at the same time more than sufficient to compromise many oper- ations that a long mission requires, as the individual astronauts may not be able to carry out their tasks over the course of an established timeline. The problems posed by space radiation seem difficult to solve and will undoubt- edly further slow down the human explo- ration of the Moon and Mars. ! RADIATION EFFECTS ON HUMANS ACUTE Felt almost immediately when a large dose of radiation is accumulated in a short amount of time. Causes nausea, vomiting fatigue, and central nervous system diseases, which can lead to changes in motor function and behavior. CHRONIC Effects can be experienced decades after exposure. Results from an accumulated dose of radiation over a long period of time. Causes increased risk of cancer, cataracts and vision impairment, degenerative cardiac disease.