We've learned Mel Gibson's wife Robyn has just filed legal papers to divorce Mel Gibson, her husband of 28 years, citing "irreconcilable differences." Pretty ironic -- Robyn signed the papers the day before Good Friday. Sources tell us there is no prenuptial agreement -- they were married in 1980, before Mel Gibson amassed a fortune estimated at $900 million back in 2006. Under the laws of California, property -- which includes earnings -- is divided 50/50. The Gibsons have 7 children, but only one -- Tom, who turns 10 tomorrow -- is a minor. In Robyn's legal papers, filed this morning in L.A. County Superior Court, she seeks joint physical and legal custody of Tom. Robyn is also asking for spousal support and attorneys fees. Robyn lists the date of separation as "to be determined." This is important, because earnings generally cease to be community property when the couple separates. There could be a skirmish over this. We're told the couple grew increasingly apart over the last few years, especially since Mel's drunk driving arrest in 2006. There have been reports that Mel has been involved with another woman, which the actor denies, but we're told the reasons for the divorce go beyond any third party.Damn. I was never really a big fan of Mel Gibson the Actor fan (except for a couple of the "Lethal Weapon" flicks), but I always admired him for being a successful, conservative actor in liberal Hollywood. And as much as libs love to tell you that religious or conservative movies don't make money, Gibson's self-produced, mega-hit "The Passion of the Christ" proved them all wrong. I knew he had been married for awhile and was passionate regarding his feelings on marriage and family, so one hopes that it wasn't adultery that played into why the marriage ended.