Article Photos: Pope celebrates last public Mass as pontiff 21/37

Bishop Guido Marini holds Pope Benedict XVI's skull cap during the Ash Wednesday mass in St. Peter's Basilica at the Vatican, Wednesday, Feb. 13, 2013.  Ash Wednesday marks the beginning of Lent, a solemn period of 40 days of prayer and self-denial leading up to Easter. (AP Photo/Gregorio Borgia)