By Michael Pearson. Richard Allen Greene and Dan Rivers, CNN

Rome (CNN) - The Sistine Chapel is ready. The new pope's clothes are laid out. Now it's up to the cardinals.

The work to elect a successor to retired Pope Benedict XVI begins in earnest Tuesday, with a morning Mass at St. Peter's Basilica.

The service - open to the public - will be the last public event featuring the 115 cardinals who will choose the new spiritual leader of the world's 1.2 billion Roman Catholics.

Cardinals taking part in the process will then walk to the Sistine Chapel, chanting prayers as they go, to begin the secret election called the conclave.

After that, the only clue the world will have of what is happening inside will be periodic puffs of smoke from a copper chimney installed over the weekend in the Sistine Chapel.

Black smoke, no pope. White smoke, success.