Late last night, NASA astronaut Scott Kelly safely returned to Earth following 340 consecutive days aboard the International Space Station. The mission will provide scientists with invaluable data about deep space exploration and whether or not humans can actually survive long-duration space travel.

Kelly arrived in Kazakhstan at 11:26 p.m. EST with Russian cosmonaut Mikhail Kornienko, who also spent 340 days in space, and Sergey Volkov, who arrived on the ISS last fall.

“Scott has become the first American astronaut to spend a year in space, and in doing so, helped us take one giant leap toward putting boots on Mars,” said NASA administrator Charles Bolden.

During his time in space, Kelly participated in nearly 400 investigations, including research about how the human body changes when subjected to long periods of weightlessness. Kelly actually has an identical twin brother, former NASA astronaut Mark Kelly, who will serve as the control for more experiments Scott is scheduled to participate in over the next twelve months.

With his successful return to Earth, Kelly has now spent a whopping 520 total days in space, which is the most of any U.S. astronaut; Kornienko, meanwhile, has spent 516 days in space, while Volkov has almost 550 under his belt.

To learn more about the mission and what Kelly did during his time in space, check out our previous posts below. While Kelly is safely back on Earth, the real interesting part will be seeing how he readjusts to gravity, and how his test results compare to that of his brother Mark.