NASA astronaut Scott Kelly and Russian cosmonauts Mikhail Kornienko and Gennady Padalka are heading to the International Space Station this Friday on a Soyuz spacecraft: One-Year Crew Set for Launch to Space Station; NASA TV to Air Live Coverage – NASA

While all previous astronaut tours on the station have been limited to less than six months, Kelly and Kornienko will spend a year aboard the space station. The goal of the  One Year Crew program is to study the effects on the human body that could occur on a long space trip in microgravity to Mars and to find ways to ameliorate or prevent negative effects.

One particularly interest aspect of this experiment will be the comparison of Scott with his twin brother and former astronaut Mark Kelly, who will remain on the ground: NASA Launches New Research, Seeks the Subtle in Parallel Ways – NASA

Last year Chris Jones wrote an extensive preview of the mission in an Esquire Magazine article called Away. Jones will post periodic updates on the mission in the coming year. Here is his first posting: Away: Five Days To Launch

Here’s a NASA video about the twins study: