More than 200 researchers conducted 30 studies on mice, insects and astronauts in space and identified six cellular and molecular changes that affect astronaut health: DNA damage, oxidative stress, changes in telomere length and the microbiome, mitochondrial dysfunction and gene dysregulation. "We now have a foundation to build on -- things we know to look for in future astronauts, including telomere length changes and DNA damage responses," said Susan Bailey, a co-author of three of the studies.