2005 Lincoln Navigator oil on axle, slow, not sure where it

Hi there!

I have some oil that seems to be showing up on my front right axle, around where I imagine the axle seal would be. However I couldnt seem to find what I was looking at in my Chiltons manual. The oil appears to saturate the whole area of that joint pictured, but I'm not entirely sure that the joint is the source of the leak. I have never seen a puddle on the ground of my driveway, but if you look at the pictures it looks like a decent bit of oil has accumulated. Could it be coming from above? It smells like the oil i would put in my engine, is this smell different from that of the oil in my gear box? The car drives fine, but if i'm losing fluid, i'd really love to know from where. Any info you may be able to provide is much appreciated. Where I should be looking, stuff like that. What is that joint called?

Thanks again.

Very Respectfully,
Steve