Latina pop superstar and actress Jennifer Lopez revealed on Ryan Seacrest's radio show Friday morning that she will not be returning as a judge for the 12th season of "American Idol."  The news follows the departure of Aerosmith frontman Steven Tyler, who revealed his decision on Thursday.  The departure of the two stars leaves the show with just Randy Jackson as a judge for next season, and his lengthy tenure with the show is in question, as well.  Rumored to be under consideration to replace Tyler and Lopez are Mariah Carey and former runner-up contestant on the show Adam Lambert, though the show's producers have so far declined to comment.