In the recent study, scientists took a closer look at the blood of Egyptian fruit bats (pictured, an animal at Henry Doorly Zoo in Omaha, Nebraska).

For its next giant leap forward, NASA plans to send astronauts to Mars by the 2030s. The 21-month trip presents unique challenges, particularly keeping people healthy during such a long space voyage. But what once seemed like an impossible solution is now gathering momentum: Hibernation.

In winter, many mammals enter a state of torpor, dropping their body temperature and slowing down their metabolism and brain activity to save energy. However, people can't hibernate for a few reasons: Our bodies can't store enough fat without harming ourselves, function at such low energy and brain activity levels, or survive a massive drop in body temperature. (Read about surprising hibernators in nature.)

Gerald Kerth, a zoologist at the University of Greifswald in Germany, studies hibernation in bats, which are smaller and easier to research than, say, brown bears.