Right on, Silvie! We still don't know what life is here at home! We have a feeling for it but can't pin it down. Check out any dictionary or
http://www.answers.com/life, which will tell you sg like life is "The property or quality that distinguishes living organisms from dead organisms ..."; talk in circles. light is absence of darkness & vv. .......
We talk and talk about it but haven't the faintest what we're talking about. We humans are really infants feeling our way around in the unknown. We've gotta do a lot more observing what is going on. I say, yeah, let's look for Martians, Titanians and everyone else we can think of.