'Space Twins' In One-Of-A-Kind Experiment

A set of identical twins are hoping to increase understanding of the effects of long haul-space travel on the human body by taking part in a one-of-a-kind experiment.

Scott Kelly is aiming to spend a year living on board the International Space Station, which would be a NASA record.

His brother Mark, who is married to former US Congresswoman Gabby Giffords , will stay on earth and act as a control in the physical experiment and analysis.

Speaking about the experiment in January, Scott Kelly said: "This is really going to help us learn a lot about the negative effects of space on our human physiology and then hopefully we'll figure out how to mitigate that."

Dr John Charles, head of NASA's Human Research Programme, said his team will compare the two astronauts to see how space affects the human body over extended periods of time.

He said: "It's a way to start using 21st century medical technology to understand what happens to people in long-duration space flight."

During his time in space, Scott will perform a number of experiments and undergo medical tests.

Scientists hope the experiment will help to prepare for a long-haul flight to Mars.

There will be one difference between the brothers after the mission: their height due to the lack of gravity.

"This time hopefully it will last long enough so that when I get back to the US I can look down at him a little bit," said Scott, joking that the lack of gravity could make him slightly taller than his brother for a time after the flight.

Russian Cosmonaut Mikhail Kornienko will join Scott on the space station, and will also stay for a year.

The mission is set to launch in Kazakhstan on 27 March.