Long-term spaceflight may have detrimental effects on liver health, according to a study conducted on mice flown aboard the space shuttle Atlantis. Experts believe the findings, which showed early signs of non-alcoholic fatty liver disease (NAFLD) in the animals after just 13.5 days in space, could have major implications for future missions to Mars and beyond, ScienceDaily reports.

Scientists have been studying the effects of spaceflight on physiology for years, although most of the research so far has focused on bone, muscle, brain and cardiovascular functions. However, several recent studies have suggested that astronauts can develop diabetes-like symptoms in space as well. This new liver study was designed to investigate metabolic drivers of those findings.

The mice spent time orbiting Earth in 2011. Once they were returned home, researchers at the University of Colorado were allowed to study and share their organs. Ultimately, they found that spaceflight appeared to activate special cells in the animal livers that went on to induce scarring. Researchers also found that the mice lost lean muscle mass and retinol (an animal form of vitamin A) and experienced rapid changes in levels of genes responsible for the body’s ability to break down fats.

As a result, the space mice began to show early signs of NAFLD, a condition characterized by the accumulation of fat in the liver, as well as potential indicators of liver fibrosis. Fatty liver disease, which is also linked to obesity and diabetes, often takes months or years to manifest in humans on Earth. However, spaceflight seemed to drastically speed up this process.