> It's not (yet) possible to shield astronauts from enough space radiation to keep them alive during the 9-month trip to Mars. I'm sorry, but this is not true.

> It's not (yet) possible to shield astronauts from enough space radiation to keep them alive during the 9-month trip to Mars. I'm sorry, but this is not true. See for example http://www.spacedaily.com/news/mars-general-03w.html http://www.spacedaily.com/news/mars-general-03w.html.