Expedition 43 has successfully left Earth. NASA astronaut Scott Kelly and Russian cosmonauts Mikhail Kornienko and Gennady Padalka are on their way to the International Space Station, and each one of them is embarking on a record-setting journey.
Kelly and Kornienko's 340-day stay will be the longest amount of time anyone has spent aboard the ISS, breaking the previous record of seven months set back in 2007. And when Kelly lands in March of next year, he will have spent a total of 522 days in space throughout his career — a new NASA record.
Padalka will break the all-time record for total time spent in space
The world (or, more accurately, off-world) record for total days in space is is held by Sergei Krikalev, who has spent more than 800 in orbit over the course of six different missions. That record won't last long — Padalka's stay will push him well past Krikalev's record by the time he lands in September. The year-long stay will be a first on the ISS, but four other cosmonauts have completed off-planet missions lasting longer than a year; those took place in the 1980s and 1990s aboard the Mir space station.
The science and technology needed to evaluate the impacts of microgravity on the human body are much better now, and that's why Kelly and Kornienko took up this mission. If we ever want to get to Mars, we have to learn a lot more about how the human body reacts to weightlessness.
NASA plans to enhance its study by also keeping close tabs on Scott Kelly's twin brother. Mark Kelly, a retired astronaut himself, will go about his regular routine while his brother orbits Earth for 340 days. Mark will obviously be living in a much different environment without the same constraints that the ISS imposes, so he's not necessarily a perfect control study. But NASA scientists hope to use the observational research they can gather from the identical twin to understand the changes that will happen to Scott on a genetic level.