Some of the physical changes associated with prolonged duration space flights are already widely known.  Muscular atrophy, for instance, begins to set in as astronauts living in microgravity environments like the International Space Station adjust to no longer needing to support their own weight.  Over the years, NASA and its peers in the international community have attempted to counter these effects through resistance training, but it remains common for astronauts to require a period of readjustment upon returning to the surface of the Earth, as their bones, muscles, and joints struggle under the seemingly overwhelming pull of the planet’s gravity.

Now, thanks to astronaut Scott Kelly and his twin brother Mark, NASA’s scientists are beginning to develop a better understanding of how space flight affects humans in a more microscopic sense: they compared the way the two men’s genes are expressed (or turned on and off) after Scott spent nearly a year orbiting the earth, far above his brother (and the rest of us) back here on the surface–the initial findings appear to be quite interesting.

“Some of the most exciting things that we’ve seen from looking at gene expression in space is that we really see an explosion, like fireworks taking off, as soon as the human body gets into space,” Twins Study principal investigator Chris Mason said in a statement.  Mason hails from Weill Cornell Medicine, Cornell University’s medical school.

“With this study, we’ve seen thousands and thousands of genes change how they are turned on and turned off,” Mason continued. “This happens as soon as an astronaut gets into space, and some of the activity persists temporarily upon return to Earth.”

After Scott Kelly returned from his 11 month stint aboard the ISS, NASA scientists and researchers immediately set about comparing his genetic anatomy to that of his brother, a now retired astronaut.  Because the two are identical twins, they share a DNA profile, making them an excellent opportunity for comparison, with Mark serving as the control for the experiment.

“This study represents one of the most comprehensive views of human biology,” Mason said. “It really sets the bedrock for understanding molecular risks for space travel as well as ways to potentially protect and fix those genetic changes.”

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However, scientists do have their work cut out for them.  Despite the excitement surrounding the unveiling of these differences in gene activation, further study is required to fully grasp what this understanding means for the future of space travel.  There are so many variables in play throughout an 11 month tour in orbit, scientists must work to decipher which elements in the Brothers Kelly lifestyles, one in orbit and one on earth, resulted in the observable differences in their anatomy.

As an example, scientists quickly discovered a difference in Scott and Mark Kelly’s chromosomes: specifically, that the telomeres, or regions at the ends of chromosomes, of Scott’s white blood cells had grown longer during his mission.  Ordinarily, telomeres, which protect chromosomes from deterioration, shorten as people age.  This would seem to be a distinct difference between the brothers that can be attributed to space travel, but scientists must first determine if the changes were the result of differences in physical activity, caloric intake or any number of other variables in play.

“Interestingly, telomerase activity (the enzyme that repairs the telomeres and lengthens them) increased in both twins in November,” NASA wrote in a statement, “which may be related to a significant, stressful family event happening around that time.”

So, as exciting as the scientific community may be about these latest announcements, there will be some time before the analysis of the differences between the two brothers manifest into a truly better understanding of how space travel affects the human body–but don’t let that dissuade your enthusiasm.  Each of these discoveries may be one small step for NASA’s Twin Study, but they promise to result in one giant leap for a space-faring mankind.

Image courtesy of NASA