Ever lain on your back, studying a starry sky, wondering if there's anything else out there?

It's possible that there could be another spot in our own solar system that supports life, or did in the past. Some planetary scientists think that Martian life, past or present, is a possibility. Bacteria live in some of the harshest environments known on the Earth, from Antarctic ice to deep sea vents - so why not the Red Planet? Earlier this year, astronomers reported finding methane gas in the Martian atmosphere. Their paper, published in the journal Science, said that gas could result either from geochemical activity or possibly living organisms.

Other experts are looking further afield in search of extraterrestrial life. But will we be able to recognize exotic life forms if we stumble across them? Are alternate systems of biology, based on chemistry involving arsenic or sulfur, rather than carbon, alive and well elsewhere? In this hour of Science Friday, we'll talk about the origins of life, and the possibility we're not alone in the universe. We're broadcasting from Tempe, Arizona this week, as part of ASU's Origins Symposium. See a web stream of the Origins Symposium here.