Getting there will be an immense challenge, as will setting up structures, creating sustainable sources of food, and battling the inhospitable elements, but sex might be the biggest risk of all.

In a new research paper published in Futures, an international team of scientists examines the challenges of reproduction on the Martian surface. It's a risky proposition, but if humans succeed in conceiving, carrying, and birthing offspring on another world it might actually be the start of a new species.

In the paper, the researchers tackle a huge number of potential problems that could crop up when humans are finally ready to rear young on Mars. The first and most obvious hurdle is the low gravity environment, which could pose a serious threat to the conception and pregnancy processes that seem so simple here on Earth.

With just one-third the gravity of Earth, Mars travelers will be subjected to a whole range of health problems. Scientists know this because astronauts who have spent months and in some cases years in space have been closely studied for changes to their biology. Lower gravity causes muscles to deteriorate rapidly and can even weaken bone structure. On top of that, astronauts sometimes experience vision problems and even changes to the shape of their brains.