Notitia Leprosi

Transit, radiation, and Mars
Today I dug up some good news and bad news for prospective Martian tourists and colonists. Mainly I looked up radiation, but I've included some other fun facts below.

First, the good news. From what I can tell, solar flares do not seem to be as much of a problem for interplanetary travel as they have been portrayed. According to a NASA article, http://science.nasa.gov/headlines/y2005/07oct_afraid.htm, solar radiation is adequately shielded by standard hull materials for spacecraft. Even a sizable flare should only result in moderate radiation sickness for the occupants of a spaceship with the 10 to 11 g/cm^2 of shielding used in current short-range craft, http://www.nasa.gov/mission_pages/stereo/news/stereo_astronauts.html, http://en.wikipedia.org/wiki/Radiation_poisoning. In fact, it may be a good idea to plan trips during maxima of solar activity since increased solar particle radiation deflects galactic radiation, which is much more difficult to shield against.

Now for some bad news. A round-trip to Mars is estimated by Robert Brit at Space.com, http://www.space.com/scienceastronomy/mars_dangers_040120.html, to entail (presumably for current spaceship hulls) something like 60 rem of radiation (1 sievert = 1 Sv = 100 rem). According to http://www.nasaexplores.com/show_912_student_st.php?id=04032381148, the monthly, yearly, and lifetime radiation dosages for astronauts considered acceptable by NASA are 25 rem, 50 rem, and 100-400 rem (lifetime numbers depend on your age and sex). Moreover, he claims that each year on the surface of Mars you can expect to soak up on the order of 30 rem. Thus, if you decide to stick around (above ground), you can expect to exceed NASA's lifetime radiation allowance within about a decade.

In addition to abundant particle radiation, Mars sports an atmosphere consisting of 95% carbon dioxide with a pressure of less than 1 KPa (c.f. earth's sea-level pressure of 101 kPa and the 30 kPa pressure on top of the Himalayas), http://en.wikipedia.org/wiki/Mars_(planet). Finally, while Mars receives only 44% percent as much light as the earth, its thin atmosphere ensures an amount of UVB electromagnetic radiation exceeding that of earth, http://mpfwww.jpl.nasa.gov/mgs/sci/fifthconf99/6128.pdf,
http://findarticles.com/p/articles/mi_qa3931/is_200301/ai_n9171725.

Oh, and the temperature? It ranges from −140 °C during the polar winters to highs of up to 20 °C.

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