Mice Flown in Space Found to Have Signs of Early Liver Damage, Study Shows The mice studied spent two weeks aboard the Atlantis space shuttle in 2011.

 -- A group of mice that spent two weeks in space on board the shuttle Atlantis were found to have early signs of liver damage, raising concerns about the possible implications for a manned mission to Mars, according to a new study.

After the rodents spent two weeks aboard the space shuttle during its final flight in 2011, researchers from the University of Colorado's Anschutz Medical Campus collected liver samples and found that the time in the micro-gravity environment had activated liver cells that could have the potential to cause scarring and other long-term damage. The results were published Wednesday in the journal PLOS ONE.

"Prior to this study we really didn’t have much information on the impact of spaceflight on the liver," Karen Jonscher, lead author of the study and an associate professor at the University of Colorado's Anschutz Medical Campus said in a statement. “We knew that astronauts often returned with diabetes-like symptoms but they usually resolved quickly."

While NASA has studied the effects of spaceflight on the human body, including bone density, muscle performance and cardiovascular function, Jonscher said the mice study leaves open the the question of whether liver damage could potentially impact humans on long-duration, deep-space missions.

"We need to look at mice involved in longer duration spaceflight to see if there are compensatory mechanisms that come into play that might protect them from serious damage," she said.

Astronaut Scott Kelly, who returned last month from one year in space, has been NASA's biggest human test subject so far when it comes to studying how living out of this world impacts the human body. Kelly and his twin brother, Mark, have been participating in tests to measure everything from bone density and metabolic performance to Kelly's state of mind.