NASA Administrator Charles Bolden, left, gives remarks during NASA's Day of Remembrance at Arlington National Cemetery gather around the Space Shuttle Columbia Memorial and Space Shuttle Challenger Memorial, Jan. 28, 2016, in Arlington, Va. Jan. 28 marks the 30th anniversary of the Challenger accident, though all of those “who lost their lives while furthering the cause of exploration and discovery.” In addition, attendees visited the graves of U.S. Air Force Lt. Col. Virgil Grissom and Lt. Cmdr. Roger Chaffee, who were killed in a fire on Apollo 1. (U.S. Army photo by Rachel Larue, Arlington National Cemetery)