King Albert II of Belgium and Queen Paola attend a papal mass at St Peter's square for the start of the Jubilee Year of Mercy, on December 8, 2015 in Vatican. Pope Francis marks the start of an extraordinary Jubilee year for the world's 1.2 billion Catholics by opening a "Holy Door" in the walls of St Peter's basilica. At 9.30 am (0830 GMT), the Argentinian pontiff will pronounce the words "Aperite mihi Porta Iustitiae" -- Latin for "open to me the gates of justice" -- and the door, which is normally bricked up, will be opened.   AFP PHOTO / ANDREAS SOLARO / AFP / ANDREAS SOLARO        (Photo credit should read ANDREAS SOLARO/AFP via Getty Images)