Concerns are mounting in Vatican circles over the health of Pope Benedict.
People who have spent time with him recently say they found him weaker than they'd ever seen him, seemingly too tired to engage with what they were saying. He no longer meets individually with visiting bishops.
A few weeks ago, he started using a moving platform to spare him the long walk down St Peter's Basilica.
Pope Benedict turns 85 in the new year, so a slowdown is only natural and expected. And given his age and continued rigorous work schedule, it's remarkable he does as much as he does: just this past week he confirmed he would travel to Mexico and Cuba next spring.
But a decline has been noted as the Pope prepares for next weekend's gruelling Christmas celebrations, which kick off two weeks of intense public appearances. And that raises questions about the future of the papacy given that Benedict himself has said popes should resign if they can't do the job.
Vatican spokesman the Reverend Federico Lombardi has said no medical condition prompted the decision to use the moving platform in St Peter's, and that it was merely designed to spare the Pontiff the fatigue of the 100-metre walk to and from the main altar.
And Benedict rallied during his three-day trip to Benin in west Africa last month, braving temperatures of 32C (90F) and high humidity to deliver a strong message about the future of the Catholic Church in Africa.
Wiping sweat from his brow, he kissed babies, delivered a tough speech on the need for Africa's political leaders to clean up their act, and visited one of the continent's most important seminaries.
Back at home, however, it seems the daily grind of being Pope -- the audiences with visiting heads of state, the weekly public catechism lessons, the sessions with visiting bishops -- has taken its toll. A spark is gone. He doesn't elaborate off-the-cuff much any more, and some days he just seems wiped out.
Popes are allowed to resign; church law specifies only that the resignation be "freely made and properly manifested".
Only a handful have done so, however. The last one was Pope Gregory XII, who stepped down in 1415 in a deal to end the Great Western Schism among competing papal claimants.
Benedict was elected Pope at 78 -- already the oldest pope elected in nearly 300 years -- he had been planning to retire as the Vatican's chief orthodoxy watchdog to spend his final years writing in the "peace and quiet" of his native Bavaria.
The Mass yesterday marked the Vatican's efforts to encourage what it calls a "new evangelisation". The missionary zeal is aimed both at achieving conversions in parts of the world where the Catholic Church is growing, including Asia and Africa, and at shoring up flagging faith in traditional Christian areas, including Western Europe.
A stream of revelations about church cover-ups of decades of sexual abuse by clergy of young people in the United States, Europe and Latin America has alienated many faithful from the church.
Benedict announced the Vatican will dedicate a special year of efforts to give "renewed impulse to the mission of all the church".
The "Year of Faith" will begin on October 11, 2012, the 50th anniversary of the start of the Second Vatican Council.
The year will provide the occasion to "reinforce our faith in God" and "to announce him with joy to mankind," Benedict said.