Pope Benedict XVI waves as he arrives to lead the Wednesday general audience in Saint Peter's square, at the Vatican October 24, 2012. REUTERS/Giampiero Sposito 

Pope Benedict XVI walks through Auschwitz's notorious gate with the phrase "Arbeit Macht Frei" (Work sets you free) during his visit to the former Nazi death camp May 28, 2006. REUTERS/Pawel Kopczynski 

Pope Benedict XVI greets the youth in front of a huge Jesus Christ portrait in Krakow May 27, 2006. REUTERS/Wolfgang Rattay 

Pope Benedict XVI posts his first tweet using an iPad tablet after his Wednesday general audience in Paul VI's Hall at the Vatican December 12, 2012. REUTERS/Giampiero Sposito 

Pope Benedict XVI prays while holding a candle light as he arrives to lead a vigil mass during Easter celebrations at the St. Peter's Basilica in the Vatican April 7, 2012. REUTERS/Alessandro Bianchi 

A body guard (C) for Pope Benedict XVI deflects the hand of a woman reaching towards the pontiff as he leaves the Basilica in the city of Ouidah in Benin, November 19, 2011. REUTERS/Finbarr O'Reilly 

Pope Benedict XVI attends a Mass celebrating the 200th anniversary of the independence of Latin American countries at St. Peter's Basilica December 12, 2011. REUTERS/Alessandro Bianchi 

A gust of wind blows as Pope Benedict XVI's speaks during his weekly audience in St. Peter's Square at the Vatican September 26, 2012.
REUTERS/Alessandro Bianchi 

Pope Benedict XVI waves as he arrives to lead the weekly general audience in Saint Peter's Square at the Vatican April 18, 2012. REUTERS/Max Rossi 

Pope Benedict XVI arrives for a meeting of religious leaders at St Mary's University College Chapel at Twickenham in west London September 17, 2010. The Pope is on a four-day visit to Britain and Scotland. REUTERS/Max Rossi 

Pope Benedict XVI waves as he arrives for the Immaculate Conception celebration prayer in Piazza di Spagna (Spain's Square) in downtown Rome December 8, 2011. REUTERS/Alessandro Bianchi 

Pope Benedict XVI leaves Oscott College seminary in Birmingham September 19, 2010. REUTERS/Leon Neal/POOL 

Pope Benedict XVI holds his cross as he leads a solemn mass in Zagreb June 5, 2011. REUTERS/Alessandro Bianchi 

Pope Benedict XVI leaves at the end of the Vespers mass to celebrate the feast of Saint Peters and Paul in the Saint Paul Outside the Walls basilica in Rome June 28, 2010. REUTERS/Tony Gentile 

Pope Benedict XVI celebrates the First Vespers and Te Deum prayers in Saint Peter's Basilica at the Vatican December 31, 2009. REUTERS/Alessia Pierdomenico 

Pope Benedict XVI arrives to lead a special audience with the Italian civil protection department at the Paul VI Hall in the Vatican March 6, 2010. REUTERS/Alessandro Bianchi 

Pope Benedict XVI arrives for the canonization ceremony of Italian nun Rosa Venerini, Mexican bishop Rafael Guizar, Italian priest Filippo Smaldone and Indiana nun Theodore Guerin in St. Peter's square at the Vatican, October 15, 2006. REUTERS/Giampiero Sposito 

Pope Benedict XVI leaves at the end of his weekly audience in Saint Peter's Square at the Vatican November 16, 2011. REUTERS/Stefano Rellandini