This image released by the Vatican shows Pope Francis celebrating mass at the Basilica of Our Lady of Guadalupe, a major Catholic shrine, on February 13, 2016 in Mexico City, Mexico. == RESTRICTED TO EDITORIAL USE / MANDATORY CREDIT: "AFP PHOTO / HO / OSSERVATORE ROMANO" / NO MARKETING NO ADVERTISING CAMPAIGNS / DISTRIBUTED AS A SERVICE TO CLIENTS == The basilica houses the image of a dark-skinned, or "morenita," Virgin Mary that Catholics believe miraculously became imprinted on a piece of fabric after she appeared before an indigenous peasant in 1531. == RESTRICTED TO EDITORIAL USE / MANDATORY CREDIT: "AFP PHOTO / HO / OSSERVATORE ROMANO" / NO MARKETING NO ADVERTISING CAMPAIGNS / DISTRIBUTED AS A SERVICE TO CLIENTS == / AFP / AFP AND Osservatore Romano / Osservatore Romano