With an eye toward preparing for eventual human missions to Mars,

NASA is considering doubling an astronaut's stay aboard the International Space

Station from six months to one year.


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The Russian news agency RIA Novosti reported this week that

the Russian space agency and its space station partners had agreed to launch a

cosmonaut and a NASA astronaut to the station in 2015 for a year-long

experimental mission.

NASA spokesman Rob Navias told Discovery News the U.S. space

agency had been "exploring the idea," but that no agreements have been signed.

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"We have had

discussions," Navias said. "A one-year increment on the ISS would be a natural

progression as part of preparations for missions beyond low-Earth orbit."

So far, only four people have spent a year or longer in

orbit during a single mission. All four are Russian cosmonauts who served

aboard the Mir space station, which was removed from orbit in 2001.

"Getting contemporary medical data with modern equipment would be

helpful," Navias said.

The station is a $100-billion research laboratory that flies

about 250 miles (about 400 km) above Earth. The partnership is led by the United States and

Russia and includes Europe, Japan and Canada.

If the long-duration mission proves successful, Alexei

Krasnov, head of human spaceflight for the Russian space agency Roscosmos, said

the partners discuss implementing year-long assignments on a permanent basis,

according to RIA Novosti.

Image: Russian cosmonaut Valeri Polyakov, who holds the  record for the single-longest stay in

space, gazes through a window on Russia’s Mir space station as shuttle

Discovery conducts a practice rendezvous on Feb. 6, 1995. Polyakov wrapped up

his 437-day, 18-hour spaceflight on March 21, 1995 — five days after a Russian

Soyuz capsule carrying U.S. astronaut Norm Thagard and two Russian cosmonauts arrived

for a series of joint missions that set the stage for the International Space

Station partnership. Credit: NASA