NASA astronaut Doug Wheelock leaves a NASA pin on the headstone of the Extortion 17, fellow service members who lost their lives during his tour of duty in Afghanistan, as part of National Wreaths Across America Day, Sat., Dec. 14, 2019 at Arlington National Cemetery in Arlington, Va. National Wreaths Across America Day is held annually to celebrate the lives of military veterans. Wheelock honored those who lost their lives in the quest for space exploration as well as fellow service members. Photo Credit: (NASA/Aubrey Gemignani)