A NASA astronaut and a Russian cosmonaut will make history in March when they begin a year-long mission on the International Space Station (ISS).

NASA's Scott Kelly and Roscosmos' Mikhail Korniyenko will study the long-term effects of spaceflight on the human mind and body during their 365-day mission.

Their mission marks the longest time ever spent on the ISS, with it being the second longest manned mission in space. From 1994 to 1995, Russian cosmonaut Valery Polyakov spent 438 days in space at the Mir Space Station.

This new mission's goal seeks to understand how longer periods in space physiologically and psychologically affect astronauts before we begin long-term manned space explorations to asteroids and Mars.

"We have progressed considerably in our understanding of the human physiology in space and in countermeasures to preserve bone, muscle and fitness since then," says Dr. Michael Barratt from NASA's Human Research Programme. "The space station programme provides us a robust framework for international collaboration that enables us to realise tremendous returns from such an experience."

Long-term exposure to microgravity, such as that present in space, has negative effects on the body. In space, bone loss is common, as well as an increased risk of kidney stones and fractures, as well as creating problems with the body's ability to heal itself. Long-term weightlessness also results in a loss of muscle mass and strength, as well as raising the risk of cardiac disturbances. Space also affects neuromuscular coordination.

Currently, most astronauts subjected to six months on the ISS show that the body doesn't adapt within that time to the conditions of space. This new year-long journey will show if that trend continues or if longer-term exposure results in better adaptability.

"If we're ever going to go to Mars some day, the International Space Station is really a great platform to learn much about having people live and work in space for longer durations," says Kelly.

Kelly is a former U.S. Navy captain who piloted a space shuttle mission in 1999 and was a commander in 2007. Korniyenko is both a former paratroop officer and a graduate of the Moscow Aviation Institute. Both men served as flight engineers on the ISS in 2010.

Both astronauts have been in a training program for their new mission for the past two years.

Kelly and Korniyenko will arrive at the ISS in March via a Russian Soyuz spacecraft.