They KNEW the environment from the tens of probes that had already been sent! Quoting: Anonymous Coward 14143765
They knew that any mammal sent beyond earth orbit ended up sick or dead.
But more importantly, you haven't been reading NASA's own press briefings. NASA knows very little about the lunar environment, and in fact is scared witless of it.
[link to science.nasa.gov
How much radiation awaits lunar colonists? A new NASA mission aims to find out.
"Not only will we measure the radiation, we will use plastics that mimic human tissue to look at how these highly energetic particles penetrate and interact with the human body," says Spence, who is the Principal Investigator for CRaTER.
So which is worse for astronauts: cosmic rays from above or neutrons from below? Igor Mitrofanov, a scientist at the Institute for Space Research and the Russian Federal Space Agency, Moscow, offers a grim answer: "Both are worse."