The feast of the Ascension falls today, 40 days after Easter (However, many dioceses in the US have transferred it to the following Sunday).
I like to celebrate this feast on Thursday because it keeps the symbolic significance of the 40 days, and also because the novena to the Holy Spirit in preparation for Pentecost starts tomorrow.
In any case, the events around Ascension and Pentecost involve Mary. The Scriptures don't say a lot about it, but what is there is very telling. Luke notes that after Jesus ascended to the Father, the disciples went back to Jerusalem to pray for the Holy Spirit. In Acts, Luke notes, "There were some women in their company, and Mary the Mother of Jesus."
At the Annunciation, the Holy Spirit came upon Mary and she became the Mother of Jesus. We can see a parallel between Luke's account of the Annunciation, and his account of Pentecost. He specifically tells us that Mary was present. This time, however, she was not alone, but was in the midst of the group of disciples. Now, at Pentecost, she becomes more fully the Mother of the Church and this happens because the Holy Spirit comes upon her as she is joined in prayer with the other disciples.