Pope Francis appears at Palm Sunday Mass at St. Peter's Square

The Vatican had refused to comment before today (April 13) on whether the pontiff would be able to participate in any of the Vatican's Holy Week celebrations, the most sacred period of the year for Christians. 

Throughout the past week, however, Francis has made surprise appearances in public, leading many Vatican officials to believe the pope would participate in the Palm Sunday liturgy in some capacity. 

Cloudy skies, intermittent wind and light rain at the start of the Mass seemed to cast a shadow over that possibility. Yet as the Mass neared its end, the sun had arrived. and soon thereafter, the pope followed. 

Francis appeared without nasal tubes, which he has been using for oxygen supply. He took time to greet the cardinals — many of whom had not seen the pope since his March 23 return to the Vatican — along with other Vatican officials in attendance.

The pope also greeted some of the diplomats present at the Mass and passed out pieces of candy to several small children in attendance, though he spent the most time with a group of religious sisters who appeared overjoyed by the pope's presence. 

Following his public appearance at the outdoor Mass, the Vatican released a video showing Francis praying inside St. Peter's Basilica, including at the tombs of St. Peter and St. Pope Pius X. 

The Palm Sunday Mass, which marks the start of Holy Week, was concelebrated by some 36 cardinals, 30 bishops and more than 300 priests. 

Argentine Cardinal Leonardo Sandri, the vice dean of the College of Cardinals, presided over the nearly two-hour liturgy and read the pope's prepared homily, which reflected on the figure of Simon of Cyrene. 

Simon, a mere passerby, was forced by Roman authorities to carry the cross of Jesus en route to his crucifixion. 

"When we think of what Simon did for Jesus, we should also think of what Jesus did for Simon — what he did for me, for you, for each of us: he redeemed the world," read the pope's message. 

"The cross of wood that Simon of Cyrene bore is the cross of Christ, who himself bore the sins of all humanity. He bore them for love of us, in obedience to the Father;" he continued. "He suffered with us and for us. In this unexpected and astonishing way, Simon of Cyrene becomes part of the history of salvation, in which no one is a stranger, no one a foreigner." 

The witness of Simon, said the pope, is that Jesus comes to encounter everyone in every situation that they might find themselves in life. 

"Jesus' passion becomes compassion whenever we hold out our hand to those who feel they cannot go on, when we lift up those who have fallen, when we embrace those who are discouraged," Francis said. 

"Brothers and sisters," the pope continued, "in order to experience this great miracle of mercy, let us decide how we are meant to carry our own cross during this Holy Week: if not on our shoulders, in our hearts." 

The Vatican's Holy Week liturgies will continue on Holy Thursday, with the Chrism Mass in St. Peter's Basilica, leading into the Easter ​​Triduum.