US astronaut Scott Kelly, who recently completed a year-long mission on the International Space Station, will retire from NASA effective April 1, the US space agency said on Friday.NASA said Kelly will continue to participate in the ongoing research related to his one-year mission, providing periodic medical samples and supporting other testing in the same way his twin brother, former astronaut Mark Kelly, made himself available for NASA's twins study during his brother's mission, Xinhua reported."This year-in-space mission was a profound challenge for all involved, and it gave me a unique perspective and a lot of time to reflect on what my next step should be," Kelly said in a statement.
Kelly said he was "humbled and excited by new opportunities" for him that support the work NASA is doing to help people travel farther into the solar system.Kelly joined the astronaut corps in 1996 and flew in space four times. He completed a 340-day mission aboard the International Space Station earlier this month, the longest continuous stay in space for an American astronaut.Kelly also broke the American record for most cumulative time in space during his one-year mission, accruing 520 days."Scott's contributions to NASA are too many to name," said Brian Kelly, director of Flight Operations at NASA's Johnson Space Centre in Houston."In his year aboard the space station, he took part in experiments that will have far-reaching effects, helping us pave the way to putting humans on Mars and benefiting life on Earth."