NASA astronaut Scott Kelly was all smiles as he spoke to earth from the International Space Station which he described as "like coming to my old home".

Kelly is on a one-year mission, the first of its kind, with plans for important research that will help doctors, scientists and mission planners better understand the physical and psychological effects of long-duration spaceflight.

"Hopefully the current crews and previous crews and future crews, not just Misha and myself, will be furthering our goals to put humans on Mars some day," said Kelly.

Kelly, age 51 and cosmonauts Mikhail Kornienko, age 54, and Gennady Padalka, age 56, arrived at the Space Station via Russian Soyuz rocket blasted off from the Baikonur Cosmodrome in Kazakhstan on Friday.

The three person crew joined Commander Terry Virts, and Cosmonauts Anton Shkaplerov and Samantha Christoforetti who were already at the space station.

Kornienko will stay with Kelly for the year-long stay.

Padalka will return to Earth in September after racking up 878 days in space, setting a new record for the total amount of time anyone has spent in space.

"The international partnership is one of the things that's made this such a success and one of the things that's most important to us right now," Kelly said.