WASHINGTON -- Space travel triggers genetic 'fireworks' - an increase in the process of turning genes on and off, a NASA study has found. 

When retired astronaut Scott Kelly returned from the International Space Station (ISS) to Earth in March 2016, NASA's Twins Study researchers collected samples from him and his twin brother Mark Kelly. 

The researchers began combining the data and reviewing the enormous amount of information looking for correlations. 

The study revealed that space travel causes an increase in methylation, the process of turning genes on and off, and additional knowledge in how that process works. 

"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," said Chris Mason, Twins Study Principal Investigator. 

“We have seen thousands and thousands of genes change how they are turned on and turned off. This happens as soon as an astronaut gets into space, and some of the activity persists temporarily upon return to Earth," said Mason. 

"This study represents one of the most comprehensive views of human biology," he 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," he added. (PTI)