Until such time, an un-terraformed Mars will present a hostile setting for venturing pioneers. First and foremost there’s the intense radiation to deal with, which will confront the colonists with a constant health burden.

Horgan said there are many big challenges to colonizing Mars, with radiation exposure being one of them. This is an “issue that a lot of folks, including those at SpaceX, aren’t thinking about too clearly,” she told Gizmodo. Living underground or in shielded bases may be an option, she said, but we have to expect that cancer rates will still be “an order of magnitude greater” given the added exposure over time.

“You can only do so much with radiation protection,” Horgan said. “We could quantify the risks for about a year, but not over the super long term. The problem is that you can’t stay in there [i.e. underground or in bases] forever. As soon as you go outside to do anything, you’re in trouble,” she said.

Horgan pointed to a recent Nature study showing that radiation on Mars is far worse than we thought, adding that “we don’t have the long-term solutions yet, unless you want to risk radiation illnesses.” Depending on the degree of exposure, excessive radiation can result in skin burns, radiation sickness, cancer, and cardiovascular disease.