In a groundbreaking new finding that has wide ramifications for our future exploration of space, scientists have determined that one of two astronaut brothers had significant changes in their DNA during their time on the International Space Station. Researchers studied NASA astronaut Scott Kelly and comapred him to his twin brother, Mark, who remained on Earth.

They looked at all aspects of Scott Kelly’s makeup, including his psychology and physiology, their, cognition, various proteins, and the DNA itself. They examined the effects of oxygen deprivation, greater inflammation, changes in nutrients, and the genes, and found that while some of these readings returned to normal once he went back to Earth, many did not.

In fact, a staggering 7 percent of genes remained different after landing compared to when he left for the ISS, and they remain different six months after his return. This could indicate that any future long-term space travel, such as a trip to Mars to form a colony, may have to take into account these dramatic changes in genetics.