That cellulose-like structure in the upper left reminds me of the inside of weathered bones I see on our prairie, but the sharply-focussed surface to the right foreground isn't like any bones I've seen. It also looks like the bole of a dead tree, broken and hollowed out. Boy, this one really is a stumper. Good entry... and good luck.
If you've ever wanted to make a difference but found it hard to believe that one person could... check out the Kiva Team Caedes discussion thread and discover that anything is possible.
-Nik