Cara Hill
According to the deleted scene 15A from the  fourth season episode , Cara Hill was a scientist in the field of exobiology assigned to the  in early 2367. She was the wife of Doctor  and came aboard with him six months prior to the episode. The script described her as middle-aged. When asked, she did not remember him or even ever having been married, except to her chosen field, and said she had come alone. 

The character was played by Marilyn Rockafellow in the deleted scene. Her costume was sold off on the It's A Wrap! sale and auction on eBay. 

Deleted material