WATCH: Astronauts Head Home After a Year in Space

Here's a fun fact about long-duration space flight: There's no shower on board the International Space Station. "It's kind of like I've been in the woods camping for a year," astronaut Scott Kelly said during a news conference late last week.

Kelly finally gets to come home and wash off the space funk on Tuesday night. He climbed into a Russian Soyuz spacecraft and closed the hatch around 4:40 p.m. ET. His capsule undocked at 8:02 p.m., and he'll touch down just before 11:30 p.m. on the chilly steppes of Kazakhstan.

While in orbit, Kelly posted hundreds of photos, and we've got a selection here.

Kelly's 340 days in orbit shatters the U.S. record for the longest space journey. Only a handful of cosmonauts have logged more consecutive days in space. Researchers are using the mission, which Kelly conducted with Russian cosmonaut Mikhail Kornienko, to learn more about how prolonged spaceflight affects the body and mind.

The study is unique partly because Kelly has an identical twin: retired astronaut Mark Kelly, who's stayed back on Earth. Studying the Kelly brothers' DNA may provide some hints about how spaceflight changes human genetics, says John Charles, the chief scientist of NASA's human research program.

Check back here later if you need a Super Tuesday break. We'll have more coverage of the landing.

Copyright 2016 NPR. To see more, visit http://www.npr.org/.