Just what is a Mozzetta? From the Catholic Encyclopedia:
A short, cape-shaped garment, covering the shoulders and reaching only to the elbow, with an open front, which may be fastened by means of a row of small buttons; at the neck it has a very small and purely ornamental hood. The privilege of wearing the mozzetta belongs properly to no one but the pope, cardinals, exempt abbots, abbots general, and the four prelates di fiochetti;... the pope's mozzetta, is always red, except that, in Easterweek, he wears a white one. As regards material, hismozzetta, during the winter half-year, that is, from the feast of St. Catherine to Ascension Day is made of velvet or of cloth according to the character of the day or ceremony; in the summer half-year it is made of satin or fine woolen material (merino). It is edged with ermine only in the winter half-year...The mozzetta is not a liturgical vestment, consequently, for example, it cannot be worn at the administration of the sacraments. Sometimes it is traced back to the cappa, this making it merely a shortened cappa; sometimes to the almutia. From which of the two it is derived, is uncertain. The name mozzetta permits both derivations. In all probability the garment did not come into use until the latter Middle Ages. It was certainly worn in the latter half of the fifteenth century as is proved by the fresco of Melozzo da Forli painted in 1477: "Sixtus IV giving the Custody of the Vatican Library to Platina". From the beginning the mozzetta has been a garment distinctive of the higher ecclesiastical dignitaries, the pope, cardinals, and bishops.