In 2015 and 2016, NASA conducted a unique experiment on twin astronauts, where one was monitored while in space and the other was on the ground. Now, the first early results from this Twins Study have been revealed.

The experiment involved astronaut Scott Kelly and his brother Mark, a former astronaut. Scott spent a year on the International Space Station (ISS) between March 2015 and March 2016, while his brother Mark remained on Earth. During that time, tests were performed on each of them to compare genetic differences between the two.

One of the main reasons for doing the study was to see how long-term spaceflight affects the human body. Although we’ve had humans permanently in space for decades now, the exact physical and mental changes that take place still aren’t clear. Getting to the bottom of this will be crucial for future long-term missions, like trips to Mars.

The preliminary results were presented on January 26 in Galveston, Texas, at a NASA Human Research Program meeting. Researchers found that Scott’s telomeres grew longer than his brother’s, which was a surprise to the scientists.

“That is exactly the opposite of what we thought,” said Susan Bailey, a radiation biologist at Colorado State University in Fort Collins, reported Nature.

The length of Scott’s telomeres returned to normal quite quickly after he returned to Earth, for reasons unknown at the moment. A separate study, due to be completed in 2018, will investigate why this happened.

Changes were also spotted in the DNA of the twins. Specifically, Scott went through less DNA methylation, the process where molecules called methyl groups are added to DNA. This was less surprising than the telomeres finding, according to the researchers.

The first peer-reviewed papers from the Twins Study are not expected until later this year or next year. But it’s clear from these early findings that it should make for interesting reading.

(H/T: Nature)