CONTEXT:

• Scientists have found no major epigenetic differences in astronaut Scott Kelly, who spent a year in space aboard the International Space Station, and his twin brother, Mark Kelly, who remained on Earth.
• Epigenetic changes involve chemical tweaks to DNA that can influence gene activity.
• The changes affect when and how a gene is read, or expressed, for its protein-encoding instructions.

 BACKGROUND:

• Space travel caused herpes viruses to reactivate in more than half of crew aboard Space Shuttle and International Space Station (ISS), according to a NASA study.
• This finding could jeopardise mankind’s future missions to Mars and beyond.
• While only a small proportion develops symptoms, virus reactivation rates increase with spaceflight duration and could present a significant health risk on future missions.