NASA sent one identical twin brother to space for a year and studied how it changed him

What happened when NASA sent one identical twin brother to space for a year!

NASA had sent one identical twin brother for a year after, to assess how the human body changes as a result of space travel using Scott Kelly and his twin brother Mark Kelly as subjects.

After spending a year in space, he was 2 inches taller.

Scott spent 340 days aboard the International Space Station, Mark stayed on Earth, giving NASA the rare opportunity to compare two identical sets of DNA.

Scott and Mark have the same genes, but Scott's year in space appears to have strongly affected the way those genes are expressed.

Researchers knew that taking humans for a short journey outside Earth's protective atmosphere has plenty of effects on the human body, like stretching your spine, shrinking your muscles, and messing up your sleep cycle - but the effects of long-term exposure to space have been less well-known.

Here are some of the most interesting results so far:

- Scott's telomeres got longer, then shrunk back to normal.
- Scott's genes showed both increased and decreased levels of methylation, a process that results in genes getting turned on and off.
- Researchers noted differences between Scott's and Mark's gut bacteria.
- By sequencing the RNA in the twins' white blood cells, researchers found more than 200,000 RNA molecules that were expressed differently between the brothers.