Astronaut Scott Kelly is returning to Earth today after spending a year in space. He’s an identical twin and is part of a study to see how the human body reacts to prolonged time in space. After spending a year on the International Space Station, he returns to Earth on March 1. Doctors will compare his vitals with his brother’s, who stayed on Earth as a control subject, to see what kind of changes happen to the human body. His return to Earth is being broadcast live.
Here’s what you need to know.
1. Kelly Holds the Record For Longest Number of Days in Space for an American Astronaut
Scott Kelly set a record for the longest number of days in space for an American astronaut in October 2015, when he hit 382 days in space, NJ.com reported. The record includes his previous time spent in space, which involved four flights including another long stint in 1996. The New Jersey native left for his yearlong mission in March.
The original record was held by astronaut Mike Fincke. When he broke the record, Kelly tweeted:
When Kelly finished his year in space, he have been in space for 522 days total throughout his career, including his year-long stay. His tour on the International Space Station is the longest continuous stay for anyone on the ISS. Prior to this, Kelly already spent 180 days in space in 1996.
The current record for anyone being in space is held by Russian cosmonaut Gennady Padalka, who spent 879 days in space. He actually traveled with Kelly to ISS in March and returned in September.
2. A Russian Cosmonaut Also Spent a Year in Space with Kelly
Kelly hasn’t spent this year in space alone. Russian cosmonaut Mikhail Kornienko was also part of the year-long study, BBC reported. Kornienko left for ISS with Kelly and will be returning to Earth with him today. Their return will be broadcast live by NASA. (You can watch his return here.)
3. When Asked About the Creepiest Thing He Encountered In Space, He Said: ‘The Toilet’
Kelly has been very active on social media sites while he’s been on the space station. He’s actively posted to Twitter, Facebook, and Instagram. He also led AMAs (Ask Me Anything sessions) on Facebook and Reddit. During his Reddit AMA, he was asked, “What’s the creepiest thing you’ve encountered while on the job.” Kelly responded, “Generally, it has to do with the toilet. Recently I had to clean up a gallon-sized ball of urine mixed with acid.” When asked why acid was involved, he answered, “The acid is added to the urine so the urine doesn’t damage the machinery that moves it through the system. It keeps it from clogging up the system.”
He also answered several other questions, such as explaining why sleep is harder on the ISS. He said that when you sleep in 0 gravity, you don’t get that gratifying sense of laying down after a long day of work. Instead, you’re sleeping in the same position that you were already in throughout the day.
4. His Photos from Space Are Popular, Including One That People Thought Was a UFO
Kelly posts photos from space to his Instagram and Twitter accounts. His photos are hugely popular and give people a great sense of what he’s experiencing in space. One of his most-talked about photos was taken in November, when people thought they spotted a UFO outside the space station. He then posted another photo later that month that generated the same buzz.
5. Kelly Will Likely Have Lost Muscle Mass and Experienced Eyesight Changes in Space
The purpose of Kelly’s year-long stint in space is to study the effects that prolonged time in space has on the human body. Typically, astronauts that spend a long time in space have a loss of muscle mass, loss of bone density, and problems with their blood circulation and eyesight, The Verge reported. Throughout his time on the ISS, Kelly collected fluid samples and went through rigorous testing to document the changes to his body.
Part of the reason for muscle and bone loss is because just walking on Earth provides exercise as the body pushes against gravity. Without that gravity, more exercise is needed. Astronauts typically work out 2.5 hours a day to help counteract this. In addition, the lack of gravity causes fluids to move to the upper body, resulting in the legs not getting the same amount of blood that they get on Earth. Blood vessels don’t work as hard, which can result in astronauts who return to Earth experiencing dizziness and fainting.
As for vision, returning to Earth typically causes swelling in the back of the eye. NASA isn’t sure what causes this. Other possible changes to the body include immune responses, bacteria in the gut, and more.