What if another Earth -- Earth II -- suddenly showed up in the sky above our Earth, and the door of possibility was opened for there to be a world which hosted its own civilizations just like ours?

Or go further back: if there was another Earth, would you go visit it?

"Another Earth" explores just those ideas, as the "science fiction romance" links an aspiring astrophysicist (Brit Marling) to a music composer (William Mapother) through tragedy. The tragedy was spurred on by another Earth suddenly appearing in the sky, closer than the moon.

Its a premise promising enough to make "Another Earth" one of HitFix's most anticipated films from this year's Sundance slate.

In one clip, Marling and Mapother sift through some get-to-know you questions: philosophies on cleaning, going to college or not, and winning an essay contest that would send you to outer space. In the other, Marling takes herself to a place where she can the new Earth clearly in the sky, as the voiceover inquires if we even know who we are as a species or race, and "stand outside ourselves and look at us."

Heavy. The Mike Cahill-directed "Another Earth" debuts in Park City on Jan. 24.