Ascentiontide offers an opportunity to defend Mark 16, as Catholics are bound by the Council of Trent to do. Not that this is a peculiarly Catholic cause, being shared, even to use only English-speaking examples, with everyone from King James's translators to their readers of whom they could not have dreamt, the Church of God with Signs Following.
And as it is in any case perfectly simple to do. That strange and increasingly unfashionable thing, Biblical criticism, purports to read the Bible "as if it were any other ancient text", but in fact subjects it to a series of methods that would be laughed out in any other literary of historical discipline. Those methods are carefully constructed to "prove" the presuppositions of that strange and increasingly unfashionable thing, liberal theology.
Thus, if two Biblical books are word for word alike, as Matthew, Mark and Luke certainly are in parts, then they must have been copied from each other, since there is no way that God could have inspired them all and, funnily enough, done so in such a way that they confirmed each other's accounts. Hence the theory of Markan Priority, that Saint Mark's Gospel was the first to be written, and that Saint Matthew and Saint Luke copied out great chunks of it word for word. And hence the theory of Q, no copy of which exists anywhere. Likewise, if Mark ends with what looks like a sort of synopsis of the post-Resurrection events recorded in the other Gospels, then that ending must be a later accretion, since there is no way that those events could actually have happened.
Jesus simply did not claim divinity for Himself, so that rules out John at a stroke. Miracles simply do not happen, a position not even compatible with agnosticism. Style simply does not develop (seriously), so Saint Paul cannot have written several of the Epistles beginning with the words, "From Paul". And so on, and on, and on. Academia is at last moving away from this sort of thing. When will the Church in practice, since of course She has never adopted it, and cannot do so, in principle? It is amazing that the account of the Ascension in Mark 16 is not the Gospel either for Ascension Day or for the following Sunday even in Year B. For that matter, it is astonishing that there are only Years A, B and C, with no Johannine Year D. Or, at least, it is amazing now. It was only too predictable a generation or two ago. But those days are, mercifully, gone.
Not that any of this should ever distract from the real point. In the words of Saint Augustine, "He withdrew from our eyes, that we might return to our hearts to find Him." In the words of Saint Jean-Marie Vianney, He left us the Mass and the Blessed Sacrament, with everything that follows from Them, so that He could remain among us physically even after having ascended. And in the words of the two men in white robes, "This Jesus, Who was taken up from you into Heaven, will come in the same way as you saw Him go into Heaven." Therefore, let us do as the Disciples did:
"And they went forth and preached everywhere, while the Lord worked with them and confirmed the message by the signs that attended it. Amen."