After two weeks in space, Atlantis spacecraft mice came home with liver damage and this seem to put the National Aeronautics and Space Administration (NASA) planned human space flight to Mars in jeopardy.

For years, researchers have been studying the effects of space travel on the human body — how the muscles, brain, and heart would respond to space. American astronaut Scott Kelly, who returned to Earth after spending one year in space, complained of joint pains, skin issues, and sore muscles.

Finding liver damage in mice that spent only 13.5 days in space could potentially affect human space flight and future deep space missions. Scientists postulate that if humans would stay too long in space, liver damage could also occur.

A NASA-planned journey to Mars in the 2030s is expected to last for one year.

Staying in space alters the human physiology because of microgravity. Space travel causes body fluids to shift, particularly during launch and orbit that causes fluid volume in the lower limbs to decrease by as much as 10 percent.

An earlier study has also found that astronauts who spent at least six months in space experience "space motion sickness" that include cold sweating, nausea, and stomach awareness. The symptoms, which improve three days into the mission, could be due to the complex interaction of the autonomic nervous system and the gastrointestinal system.

Lead author Karen Jonscher from the University of Colorado explained that an induced fibrosis in mice, even with unhealthy diet, can take several years. What their study found was rapid fibrosis after a mere two weeks in space, without even changing the diet.

She added that the liver damage could have been due to the spaceflight stress and Earth re-entry. Whether the same mechanism would apply to a human liver is still unknown.

In the past, astronauts who returned from space had symptoms of prediabetes, which eventually resolved without intervention.

Could humans have a physiologic- protective response to liver damage?

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

Photo: Reinhard Link | Flickr