President Obama and first lady Michelle Obama walk with Pope Francis upon his arrival at Joint Base Andrews outside Washington, Sept. 22. (CNS photo/L’Osservatore Romano handout)

U.S. President Barack Obama speaks to Pope Francis during an arrival ceremony on the South Lawn of the White House in Washington Sept. 23. (CNS photo/Joshua Roberts)

Pope Francis addresses U.S. President Barack Obama and guests during a welcoming ceremony on the South Lawn of the White House in Washington Sept. 23. (CNS photo/Paul Haring)

U.S. President Barack Obama and Pope Francis walk together at the end of an arrival ceremony on the South Lawn of the White House in Washington Sept. 23. (CNS photo/Joshua Roberts)

U.S. President Barack Obama looks on as Pope Francis signs a copy of an encyclical at the White House Sept. 23 in Washington. (CNS photo/L’Osservatore Romano handout via Reuters)

U.S. President Barack Obama and first lady Michelle Obama introduce their Portuguese water dogs, Bo and Sunny, to Pope Francis in the Oval Office at the White House Sept. 23 in Washington. (CNS photo/L’Osservatore Romano handout via Reuters)

People wait for Pope Francis to drive past along a street in Washington Sept. 23. (CNS photo/Alex Brandon, pool)

Pope Francis arrives to the Cathedral of St. Matthew the Apostle for a meeting with U.S. bishops Sept. 23 in Washington. (CNS photo/Jonathan Newton, pool)

Pope Francis addresses U.S. bishops at the Cathedral of St. Matthew the Apostle in Washington Sept. 23. (CNS photo/Lisa Johnston, St. Louis Review)

Pope Francis celebrates Mass and the canonization of Junipero Serra at the Basilica of the National Shrine of the Immaculate Conception Sept. 23 in Washington. (CNS photo/Tony Gentile, Reuters)

Pope Francis raises a chalice as he celebrates Mass outside the Basilica of the National Shrine of the Immaculate Conception Sept. 23 in Washington. (CNS photo/Paul Haring)

Nuns leans out to see Pope Francis as he greets and blesses seminarians, novices and other guests inside the Basilica of the National Shrine of the Immaculate Conception in Washington Sept. 23. (CNS photo/Jim Bourg, Reuters)

Pope Francis waves as he leaves the Basilica of the National Shrine of the Immaculate Conception after celebrating Mass and the canonization of Junipero Serra Sept. 23 in Washington. (CNS photo/Paul Haring)

Pope Francis addresses a joint meeting of the U.S. Congress in the House Chamber on Capitol Hill in Washington Sept. 24. (CNS photo/Joshua Roberts)

Pope Francis addresses a joint meeting of Congress at the U.S. Capitol in Washington Sept. 24. In the first such speech by a pope, he called on Congress to stop bickering as the world needs help. (CNS photo/Paul Haring)

Pope Francis addresses a joint meeting of Congress at the U.S. Capitol in Washington Sept. 24. In the first such speech by a pope, he called on Congress to stop bickering as the world needs help. (CNS photo/Paul Haring)

Pope Francis pauses in front of the sculpture of St. Junipero Serra in Statuary Hall at the U.S. Capitol in Washington Sept. 24. (CNS photo/Michael Reynolds, pool)

Pope Francis appears with leaders of Congress, Vice President Joe Biden (second from left), Cardinal Donald W. Wuerl (right) and Archbishop Joseph E. Kurtz (left) on the west terrace of the U.S. Capitol Sept. 24 in Washington. (CNS photo/Matthew Barrick)

Pope Francis is welcomed to the Speakers Balcony at the U.S. Capitol by members of Congress Sept. 24. (CNS photo/Doug Mills, pool)

Pope Francis arrives for Mass and the canonization of Junipero Serra at the Basilica of the National Shrine of the Immaculate Conception in Washington Sept. 23. (CNS photo/Bob Roller)

Pope Francis stands in the Blessed Sacrament Chapel for private prayer at the Cathedral of St. Matthew the Apostle, where he met with U.S. bishops in Washington Sept. 23. (CNS photo/Mark Wilson, pool)

A girl hugs Pope Francis as he visits with people at St. Maria’s Meals Program of Catholic Charities in Washington Sept. 24. (CNS photo/Paul Haring)

Pope Francis greets workers and clients at St. Maria’s Meals Program of Catholic Charities in Washington Sept. 24. Pictured from left are Katie B. English, a volunteer from Rockville, Md., and client Frank Crosier. (CNS photo/Jaclyn Lippelmann, Catholic Standard)