There’s been a lot of talk lately about creating a human colony on Mars, but at least a couple of experts believe that’s totally bunk. Charles Wohlforth, a science writer, and Amanda Hendrix, a planetary scientists, have penned a column in the Los Angeles Times throwing cold water on the idea and claiming that our biology simply won’t allow it, no matter how good our technology is.

Even a short mission to Mars and back would be catastrophic to human health, let along a long-term colony, which the authors described as “out of the question.”

“NASA doesn’t talk about this much. Starry-eyed with space enthusiasm, most science reporters haven’t covered this aspect of the story either,” they write.

The big problem is galactic cosmic rays (GCRs), or particles that are sent through space by exploding stars. These particles include iron nuclei traveling near the speed of light. While these doses of radiation are tolerable on the International Space Station for a short period of just a few months, a long-term mission to Mars would result in quite a problem from GCRs, resulting in cancer and other medical problems.

And it’s not really possible to shield astronauts from GCRs due to physics, the authors claim.

“The most effective element to stop GCRs is hydrogen, making water an ideal shielding material,” they write. “Indeed, water in our atmosphere protects us on Earth. But it takes two meters of water to filter out about half the radiation, and a cubic meter of water weighs 2,205 pounds. Carrying enough water to insulate a spacecraft is far beyond current capabilities.”

And that’s for the trip there. Once you’re on Mars, there are more problems. The Martian atmosphere would force humans to live underground to protect themselves from radiation. And it begs the question: if we have to live underground on Mars anyway, what could possibly happen to Earth that would make living underground not just as viable here?

Of course, the authors acknowledge that space colonization will happen at some point, hopefully, but the destination shouldn’t be Mars if we’re talking abou ta permanent settlement, but rather Saturn’s moon Titan, which has a thick nitrogen atmosphere and lots of water. It is the closest thing we have to Earth, and we wouldn’t need radiation shielding or pressure suits. Unfortunately, it takes seven years to get there.