He was the pilot of the Discovery space shuttle mission that upgraded the Hubble Space Telescope in December 1999. His flight in 2004 was postponed until 2007 following the 2003 Columbia space shuttle disaster, when he flew as the mission commander on STS-118. The New Jersey native is the twin of the US astronaut Mark Kelly. Scott also launched aboard the Soyuz TMA-M spacecraft in October 2010 to serve a tour of duty on the International Space Station (ISS). In March 2015 Scott and cosmonaut Mikhail Kornienko began a 340-day stay aboard the ISS to gauge the physiological and psychological impacts of long-duration space flight. Mark stayed on the ground during Scott’s yearlong flight, serving as an experimental control that would allow scientists to detect genetic changes that spaceflight induced in Scott. After their return, multiple studies revealed in early 2017 several interesting preliminary developments in Scott’s body compared to that of his twin brother, including an apparent decrease in bone formation, a slight decrease in thinking speed and accuracy (shortly after touchdown), and a lengthening (improvement) of telomeres in his white blood cells during the mission and a shortening of them upon his return. Telomeres lie at the ends of our chromosomes and indicate our genetic age.