Mice that spent 91 days aboard the International Space Station, a record for any rodent, had thinner skin than the mice that stayed on Earth. Researchers are studying these ‘astromice’ to get a better understanding of the effect of a weightless environment on animal skin. The study, published in the new journal NPJ Microgravity, was one of 20 experiments that could have important implications on the physiological impact of long-duration spaceflight.

“There has been anecdotal evidence of skin problems in astronauts on orbit, including slow healing of scratches, and some crew members have had nonspecific rashes,” Julie Robinson, NASA’s lead space station scientist, told Discovery News.

Researchers wanted to understand if there was more to the skin problems astronauts often reported. Six mice were sent to the International Space Station in a special box called the ‘Mouse Drawer System.’ Of the six mice that were initially sent to space, only three survived.

Researchers studying the skin of the mice that survived found that the second layer of the skin, the dermis, had thinned significantly. The scientists also found a bizarre change in the animals' hair follicles. Betty Nusgens, one of the study’s author from the University of Liege, told the BBC that the cycle of hair was “disturbed.” While mice hair usually grows and then stops in a specific cycle, researchers found the cycle was in the opposite stage of where it should have been.

Researchers admit that the findings are preliminary, as they could only study three mice, and warn against projecting the results directly onto humans. While interesting and unique, it’s unlikely that researchers will be able to replicate the study any time soon with other animals for the same length of time.

“These results can be considered as a warning signal to space program policymakers to perform clinical investigations on the astronauts’ skin to evaluate a potential thinning,” Nusgens told Discovery News.