ISS year-long mission

The ISS year-long mission was an 11-month-long scientific research project aboard the International Space Station, which studied the health effects of long-term spaceflight. Astronaut Scott Kelly (ideally suited for the experiment as the identical twin of Mark Kelly) and cosmonaut Mikhail Kornienko spent 340 days in space, with scientists performing medical experiments. Kelly and Kornienko launched on 27 March 2015 on Soyuz TMA-16M along with Gennady Padalka. The mission encompassed Expeditions 43, 44, 45 and 46. The pair safely landed in Kazakhstan on March 2, 2016, returning aboard Soyuz TMA-18M with Sergey Volkov. The mission supported the NASA Twins study, which helps shed light on the health effects of long-duration spaceflight, which is of interest for Mars missions especially.

On 12 April 2019, NASA reported medical results from the NASA Twins Study which demonstrated several long-lasting changes, including those related to alterations in DNA and cognition, when one twin was compared with the other.