2005 Ford Crown Vic rear axle leaking?

its a 2005 ford crown vic ex state trooper , we have had it for about 20,000 miles now , has 112000 miles now and i just looked under neath the car today after its been sitting in the garage for about a week now and right where the driveshaft goes into the axle houseing its leaking right there, there is a big puddle of oil is this the rear main seal or is it worse then it looks im hoping that isnt the case what are your thoughts?