The next big leap? Crewed missions to the moon and Mars, allowing humans to explore the terrain and build bases. But first, scientists need to answer some big questions about the impacts of long-duration space travel on the human body – how humans react to life in microgravity for a month or longer.

Right now, our best approximation is life on the International Space Station, which houses an international crew of six people, 250 miles above Earth. Each astronaut usually stays on the station for about six months. This living laboratory shows the many ways that living in space can take its toll. Muscles deteriorate, bones become less dense and exposure to cancer-causing radiation increases.

Another toll is an eye condition that causes blurred and deteriorating vision, and can ultimately end in blindness. It’s called SANS, for Spaceflight Associated Neuro-Ocular Syndrome, and Professor Ross Ethier is working with NASA to understand its causes.

About 40 percent of astronauts experience these symptoms after spending a month or longer in microgravity. But some never do. “That’s one of the mysteries of SANS,” says Ethier, a professor in the Coulter Department of Biomedical Engineering and Georgia Research Alliance Lawrence L. Gellerstedt, Jr. Eminent Scholar in Bioengineering. “It’s a very mysterious condition. We don’t really understand why this occurs.”

One major challenge is getting a good view of the condition. For a variety of reasons, conducting an MRI in space is not an option. So, Ethier and his team recruited volunteers to undergo MRIs while lying in an inverted position, with heads tilted downwards. This changes the pressure around the brain, mimicking some of microgravity’s effects and allowing a closer look at the eyes under such conditions.

NASA also gives astronauts MRIs before and after spaceflight, collecting important data on its physical effects. Ethier’s team been given access to this data as well, allowing them to illuminate properties of the optic nerve and the sheath that protects it. Ethier aims to determine what makes some astronauts more vulnerable to SANS than others and discover countermeasures to protect all space travelers.

“This has to be solved before we can venture out farther,” Ethier says. “I think they’re most worried about a Mars mission. It’s not like you can just whip back to Earth and get a new pair of glasses.”

The 2020s are here – with a bang – and one thing is certain: the human desire for exploration is as pressing as ever. As craft and crews from around the globe venture farther into space and stake their footholds, the opportunities will only multiply.

And so will the challenges. For engineers, the decade ahead is filled with plenty of successes to celebrate as well as new intriguing problems to solve.