By Genevieve J. Essig
How did NASA astronaut Scott Kelly give the world some "perspective" on Earth Day this year?
Scott Kelly, who is spending a year aboard the International Space Station, posted his first "geography quiz" photo on Earth Day. He plans to tweet a photo taken from the station of an undisclosed location on the planet every Wednesday and invite viewers to guess what it depicts. Follow him @StationCDRKelly.