What are the unsolved problems in science today? My list:
Origin of life: this is one where we really seem to be closing in. I would be surprised if it's still unsolved twenty years from now. There are still plenty of crucial steps to be filled in. Finding life on another planet would probably help answer a lot of questions.
What is dark matter? It's probably some new particle, but all attempts to detect it have failed. No clue as to when or if this one can be solved.
And how about dark energy? This one is a real stumper.
What is consciousness? I can't decide if this is a real problem or not.
And then there are questions which we may never have any answers too: The origin of the universe, the nature of time, and why it is like and unlike space.
Anybody got any other good ones?