If you don't know who Scott Kelly is, it's about time you do! Scott Kelly has been an astronaut for NASA for the past 20 years, and is soon to "retire." He'll still be on NASA's payroll, as they have debriefing and several tests they want to perform on him. He also says, "I would love to stay as involved with human spaceflight as I can. I'm a huge believer in it," so most likely, he'll still be contributing more in the future.

Here are some highlights about his life and year in space:

He's spent a record-breaking year in space.

That's right, an entire year. Which is less than the record 437 days that Russia set in the 1990s, but breaks all sorts of American records. The mission began in March last year, and just returned on March 2nd. Throughout the year, they spent 342 days in space, circled the Earth with a total of 5,440 orbits, and traveled a total of 143,846,525 miles. This also makes Scott Kelly the first American to spend over a year consecutively in space. He also holds the American record for most days total, with over 500 days in space.

The year in space was shared between Russia and the U.S.

Both countries were to choose veteran astronauts for this mission. NASA's was--obviously--Scott Kelly, and Roscosmos, the Russian Federal Space Agency, chose cosmonaut (Russian astronaut) Mikhail "Misha" Kornienko. NASA considers this collaboration to be the "embodiment of significant international collaboration in biomedical risk reduction research." The research done to see what affects the year had on their bodies will require further collaboration as well. Science always progresses faster when it works collaboratively rather than competitively, so this is a hopeful sign for things to come!

Other astronauts were also on the International Space Station, but only those two astronauts stayed there all 340 days consecutively.

He might be retiring, but NASA's still studying him for the next year.

The most important part of the mission is actually yet to come! NASA will be conducting several studies to see how the human body might respond to long-term space missions. In particular, they are interested in the effects of space travel -- and microgravity (less gravity than exists on Earth) -- on bone density, muscle mass, strength, and vision. They are also worried about how space life can get to a person's head. Scott Kelly has admitted the year felt long and lonely, something which may cause some concern, but overall he seems to have made it through fine.

Currently, Kelly's been having some problems readjusting to Earth's gravity, with swollen and sore legs and stiff ankles, knees, and hips. He says it's already feeling better, which is a good sign for future astronauts. Of course, NASA's tests will be much more thorough and could possibly highlight some potential problems, but hopefully the tests will be positive enough to lead to more long space trips.

Scott Kelly has an astronaut twin, both of whom are being studied by NASA.

Captain Mark Kelly retired from NASA in 2011 to help his wife, former Arizona Representative Gabby Giffords, with her recovery from a shooting in Tuscon. But because Mark Kelly did not go back into space, NASA has been using him as a sort of "control" as a comparison to the effects of space on his brother, Scott.

The studies require 10 investigations, which take place across 12 different universities, the NASA biomedical laboratories, and the National Space Biomedical Research Institute Consortium.

*Fun fact: the Kelly brothers are the only twins to ever both go to space.

"The Martian" may soon be a reality.

Hopefully not the leaving-Matt-Damon-behind part. But NASA does have its eyes on Mars as its new frontier. If all goes to plan, then we'll see astronauts on Mars sometime during our lifetime.

A trip to Mars would take about six months there and six months back. Ideally, NASA is shooting for a three-year mission so that the astronauts have ample time to do research on Mars. The analysis done on the effects of long space travel will help determine what NASA will need to do to make this trip a reality without damaging the health of its astronauts. #JourneyToMars

Bonus: Obama's welcome-home tweet:

While not scientifically important, you gotta love a good dad pun about science.

Bill Nye (the Science Guy) was quick to tweet as well, and his wasn't too bad either, pointing out the important things:

And last but not least -- for the Scripps Students:

Scott Kelly has a -- very loose -- connection to Scripps College! Remember how I said he has a twin, Mark Kelly? Pictured above is Mark with his wife, former Congresswoman and activist Gabby Giffords, who graduated from Scripps in the Class of 1993.

Welcome home, Scott!