PHOTOS: Best of Scott Kelly's #YearInSpace pics

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Space superman Scott Kelly's yearlong mission is one for the NASA history books.

The NASA astronaut has been living at the International Space Station since last March. By the time he lands in Kazakhstan on Tuesday, he will have spent 340 consecutive days in space, a U.S. record.

Kelly will have completed 5,440 laps around the planet. Logged 143.8 million miles. Welcomed nine visiting spacecraft. Shared the place with 14 other humans, including his roommate for the long haul, Russian cosmonaut Mikhail Kornienko, also returning to Earth.

He drank nearly 200 gallons of recycled urine and sweat, collected from himself and everyone else on board.

He snapped hundreds of breathtaking pictures of the home planet and posted them on Instagram and Twitter as @StationCDRKelly, not to be confused with ShuttleCDRKelly, retired astronaut Mark Kelly, his identical twin. The brothers have taken part in an unprecedented twins study over the past year.

The 52-year-olds say they're proud to have served as guinea pigs for future Mars expeditions. For NASA, getting astronauts to Mars in 20 years is what this yearlong mission is all about.'

PHOTOS: Click through the gallery above. You can slide the thumbnails over for more photos.