If the goal is to colonize space one day, then we’ve got to step up our game on figuring out whether humans can even have babies up there in the first place. China is trying to answer that question now after becoming the first country to send artificial human embryos into space to study how microgravity and cosmic radiation affect early human development.

Live Science reports that the embryo-ish structures arrived at China’s Tiangong Space Station aboard the Tianzhou-10 cargo mission earlier this month. The spacecraft carried with it the usual bounty of astronaut goodies, like fuel, food, and equipment. The care package also included human stem cells engineered to mimic embryos during the earliest stages of development. Scientists say the structures can’t become actual babies, thus sidestepping some of the trickier, ickier ethical issues that situation would spark.

Researchers from the Chinese Academy of Sciences designed two different embryo models representing development between 14 and 21 days after fertilization. One re-creates the moment an embryo attaches to the uterine wall, and the other simulates the stage where cells reorganize into the basic blueprint for organs and tissues.

Space Wreaks Havoc on Human Bodies, Presumably of All Stages

The embryos spent five days developing in orbit before being frozen and prepared for return to Earth, where scientists will compare them against identical samples grown in labs on the ground.

It’s all rather sci-fi, but that’s the practical reality of humanity’s ambition to colonize space. Any long-term plan to live on the moon or Mars will eventually have to confront whether we can actually have normal human children on another planet, where conditions are quite different from our own.

We’ll see what observations the astronauts make in their study, but from everything we know so far, the outlook isn’t great. Previous studies have found that cosmic radiation can damage embryos and reproductive cells. Microgravity confuses sperm. And, just generally speaking, space wreaks havoc on the adult human body, so it’s safe to assume it can probably do a number on an embryo and a newborn.