Mom or not?

This post, The Mission of Older Moms, at Faith & Family Live is taking up a huge amount of space in my brain.  I can't stop thinking about it.  Granted, I've been thinking about what kind of a mom I am more than usual given my recent change in mom circumstances.  I am not an "older" mom, I mean, hey, 50 is approaching, but not for a couple of  years.  I had my children when I was young and now find myself with adult children, who live far away.  Most of my friends, even my own siblings, have young children though we are all very close in age.  And by young, I am talking about elementary school age. 
It seems every time I meet new people there is surprise on their faces when I tell them my children are adults.
But that is really beside the point.  The point is, now I have one less role to define myself with and frankly, I feel a bit empty.  And surprised.  Logically I know I am still a mom, just like my mom is still a mom, even though her youngest is 41. 
I mistakenly thought that having a career would be a protective factor in not feeling this way.  I thought I would just involve myself more fully in my work and be more productive.  It's not happening according to plan at this point.  I am no longer the mom who has children, I have adults and it is so different from having children.  What will fill this space now?  I am waiting on the next sign from God, but if anyone has any ideas, I am open.