Scott Kelly become longest-serving US astronaut in space

US astronaut Scott Kelly, commander of the current Expedition 45 crew on the International Space Station (ISS), has become the longest-living US astronaut on the orbiting laboratory.

On October 16, Kelly began his 383rd day living in space, surpassing US astronaut Mike Fincke's record of 382 cumulative days.

The feat has come just before the 15th anniversary of continuous human presence on the International Space Station (ISS).

On October 29, Kelly will break another record on his 216th consecutive day in space, when he will surpass astronaut Michael Lopez-Alegria's record for the single-longest spaceflight by an American. Lopez-Alegria spent 215 days in space as commander of the Expedition 14 crew in 2006.

Kelly is scheduled to return to Earth on March 3, 2016, by which time he will have compiled 522 total days living in space during four missions.

Kelly is not the only human breaking records for time in space.

Expedition 44 commander Gennady Padalka broke the 10-year-old record for the number of cumulative days in space June 28 as he reached 804 days in space.

When he returned to Earth on September 11, Padalka had spent 879 days living and working in space.

"Kelly, Padalka and over 200 people who have visited the space station are contributing to the development of capabilities to enable a sustainable human presence in deep space," NASA said in a statement.

Breaking such a record for time in space is important because every additional day helps us better understand how long-duration spaceflight affects bodies and minds, which is critical to advancing NASA's journey to Mars.

"Fifteen years of living and working off the Earth also is improving the quality of our lives here on Earth as scientists and engineers apply the knowledge gained from investigations aboard the unique microgravity laboratory," the statement read.

As part of the one-year mission along with cosmonaut Mikhail Kornienko, Kelly will continue to add to his record and to our understanding of the effects of long-duration spaceflight.

The pair arrived at the space station in March and are participating in studies during their 342 days in space that provide new insights into how the human body adjusts to weightlessness, isolation, radiation and stress of long-duration spaceflight.

Kelly's twin brother, former astronaut Mark Kelly, will participate in parallel twin studies on Earth to help scientists compare the effects on the body and mind in space.

"The investigations in progress on the space station will help scientists better understand how to protect astronauts as they travel into deep space and eventually on missions to the Red Planet," the US space agency noted.

Kelly is scheduled to return to Earth on March 3, 2016, by which time he will have compiled 522 total days living in space during four missions.