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.”