As of today, Scott Kelly now officially holds the record for the longest consecutive amount of time spent in space by an American astronaut. The previous record holder was Spanish-American astronaut Michael López-Alegría, who spent 215 consecutive days in space in 2007. Today marks 216 consecutive days for Kelly, who launched into space on March 27th of this year. His number count is only going to grow, too, as he's slated to spend a total of 342 days on the International Space Station before coming back home.

Kelly has also spent the longest cumulative time in space out of any American astronaut: a whopping 396 days. When he is done with this mission, he'll have racked up a total of 522 days in space over the course of four space flights. As impressive as these stats are, Russian astronauts will still have Kelly beat. The longest consecutive spaceflight was done by Valeri Polyakov, who spent nearly 438 days on the former Russian Mir space station. And Gennady Padalka, who recently stayed on the ISS with Kelly, has spent a combined 878 days in space.

Both Kelly and Russian cosmonaut Mikhail Kornienko are taking part in NASA's One-Year Mission, in which they spend nearly an entire year aboard the ISS. The purpose of the mission is to study the effects of long-term spaceflight on the human body. Living in a microgravity environment for a while is known to cause weird health effects, such as the deterioration of skeletal tissue and eyesight problems. NASA wants to understand these health risks better, since a human mission to Mars will likely require astronauts to spend many months to a year in deep space. To aid with the One-Year Mission, Kelly's twin brother Mark Kelly is staying on Earth as a "control" test subject. Researchers plan to compare the physiological differences between the brothers when the mission is over, to see how much space changes the body.