Today at 3:42 p.m., two men will be launched into space on a year-long mission that will test the limits of human spirit.

NASA astronaut Scott Kelly and Russian Cosmonaut Mikhail Kornienko will spend almost 12 months aboard the International Space Station (ISS). Most missions last only four to six months, but these brave humans will act as "guinea pigs" to help us understand how the body adapts to long-duration space flight. These insights could help bring us closer to sending people to Mars, and could even have implications on Earth, such as how to help patients recover from long durations of bed rest.

The astronauts will break records by spending the most cumulative time spent in space; the previous record was 382 days, and this new mission will last 522.

Long exposure to zero gravity can lead to symptoms such as "changes to the eyes, muscle atrophy and bone loss." Human psychology can also be affected by factors of long space missions, such as the cramped quarters astronauts are forced to live in.

"Functional studies will examine crew member performance during and after the 12-month span. Behavioral studies will monitor sleep patterns and exercise routines. Visual impairment will be studied by measuring changes in pressure inside the human skull. Metabolic investigations will examine the immune system and effects of stress. Physical performance will be monitored through exercise examinations. Researchers will also monitor microbial changes in the crew, as well as the human factors associated with how the crew interacts aboard the station," NASA stated.

While Scott Kelly is in space, his identical twin, retired NASA astronaut Mark Kelly, will undergo comparative genetic studies to assess the changes imposed by the long space flight. The experiments include blood samples along with psychological and physical tests. 

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