VATICAN CITY - Tuesday's grandiose mass in St Peter's Square to inaugurate Pope Francis, the new leader of the world's 1.2 billion Catholics, will feature symbolic rituals and spectacular imagery.
Following are the main stages in a rare and historic event expected to last around two hours, with dozens of religious and world leaders as well as hundreds of thousands of pilgrims expected.
The pope will leave his temporary Vatican residence, Casa Santa Marta, a few minutes before 9:00 am (0800 GMT) for a tour through the throngs in St Peter's Square aboard a papal vehicle.
Vatican spokesman Federico Lombardi said it would be a "long tour" of the famous square, lasting until around 9:15 am when Francis will go into St Peter's Basilica, to the sacristy by Michelangelo's Pieta, to don his vestments for the mass.
Francis will begin with a stop at the tomb of St Peter, regarded as the first pope, under the basilica's main altar. The mass will be celebrated on the square outside -- where tradition holds that Peter was crucified in around 67 AD.
The first Latin American pope will be accompanied to the observance at the tomb by around 10 patriarchs and top archbishops of the Eastern Catholic Rite who will co-celebrate the mass along with the other cardinals.
Two key symbols of the papacy -- the Fisherman's Ring and the pallium -- as well as an ornate Bible will have been placed at the tomb the night before.
The pallium -- the same as that used for Francis's predecessor Benedict XVI -- is a strip of wool worn over the shoulders recalling the role of Jesus as a good shepherd. Five red crosses on the vestment recall the wounds of the crucified Christ.
The Fisherman's Ring, made of gold-plated silver, bears the image of a bearded and haloed St Peter holding a pair of keys -- representing the moment Peter was given the keys to heaven.
The ring originally served as both a symbol of the papacy and a seal, but these days the pope has a separate seal with which to mark documents.
Two leading cardinals will bear the objects outside the basilica in a procession during which the prelates will sing a special litany of saints titled Laudes Regi (Praises of the King).
At the altar in front of the basilica, Cardinal Jean-Louis Tauran will bestow the pallium on the pope, who will then receive the Fisherman's Ring from Cardinal Angelo Sodano.
A ritual will follow in which six cardinals will swear their obedience to the pope on behalf of the three hierarchical levels of the College of Cardinals.
The mass proper is set to begin at 9:30 am, to be co-celebrated by around 180 clergymen including cardinals, patriarchs and archbishops and Adolfo Nicolas, the superior general of the Jesuit order to which Francis belongs.
The Vatican said about 250 bishops and archbishops will be seated to the left of the altar along with clergy from other Christian churches.
More than 130 diplomatic delegations will be seated on the right, while behind them will be representatives of the Jewish, Muslim and other non-Christian faiths, followed by some 1,200 priests and seminarians.
The liturgy will be that of St Joseph, the patron saint of the universal Church, whose feast day falls on Tuesday.
One detail is that the gospel will be sung in Greek only instead of both Greek and Latin as tradition normally dictates to embrace both Eastern and Western rites. Latin dominates many other parts of the mass, Lombardi noted.
The pope's homily will be in Italian.
Music will include "Tu Es Pastor Ovium" (Thou Art Shepherd of the Sheep), a rarely performed motet by Giovanni Pierluigi di Palestrina composed in 1585 for the enthronement of Sixtus V.
The mass will end with the singing of the Te Deum.
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