Nasa's Scott Kelly to Return From ISS Next Week

Kelly paved the way for future missions including Mars when he embarked on a one-year mission. The year-long endeavour has seen Kelly accomplishing several key missions, including growing the first space vegetable and flower, the US space agency said in a statement.

Nasa has partnered with other space agencies to conduct numerous human research investigations to see how the human body changes during a year in space.

Coinciding with the one-year mission is the twins study. Scott's identical twin brother Mark, himself a former astronaut, is spending the year on Earth, enabling researchers to focus on a near-identical comparison of the brothers' genomics profiles - something never captured before in human space research.

This new field of study, akin to personalised medicine, produces so much information and data to analyse that it's hard to imagine.

"The mission will continue even after Scott returns," said John Charles, chief scientist of the Nasa Human Research Programme.

"For the one-year mission research, we will be collecting post-flight medical data three-months and six-months after he is back on Earth. For the twins study research, we will continue to collect data as far out as a year after his return," he added.

The post-flight data are as important as the inflight data to help scientists learn how to send humans safely to Mars and return them safely to Earth.

To date, Nasa has approximately 15 years of data from the space station about how space affects the human body on six-month missions.

Now, the "Human Research Programme" is building on that foundation by proposing more international collaboration on future one-year space station missions.