(Photo: Jeremy Burgin via Flickr/Creative Commons)

(Photo: Jeremy Burgin via Flickr/Creative Commons)

Many of  us believe finding some form of  life beyond our own planet is inevitable,  and the recent discovery of Earth-like planets – in a region where liquid water could exist on a planet’s surface – has renewed excitement about eventually finding extra-terrestrial life.

However,  two Princeton University researchers suggest those expectations may be more based in optimism rather than scientific fact.

Princeton’s Edwin Turner  and David Spiegel wanted to separate fact from expectation.

So they took what science currently knows about the existence, or likelihood of extra-terrestrial life, and performed a Bayesian analysis, which evaluates just how much of what is considered to be a scientific conclusion comes from actual hard scientific fact and what comes from assumptions made by the scientist involved.

What the duo found will disappoint those counting on meeting ET.

In a paper published in Proceedings of the National Academy of Sciences, Turner and Spiegel report finding little supporting scientific evidence that life exists, or could exist, beyond our own planet.

Instead, they found that most of what has been concluded about the possibility of extra-terrestrial life has been taken from what scientists know about the origins or emergence of life on early Earth.  And that our expecting life to be found on Earth-like exoplanets mostly centers on the assumption of what could or would happen if conditions similar to those that allowed life on Earth to flourish were found elsewhere.

Taking what we already know about life on other planets, the researchers say it’s very possible Earth may be an oddity compared to other planets, because life took root quickly and early in our planet’s history.  If this is true, then the chances of Earth-like planets hosting life would be low.

“If scientists start out assuming that the chances of life existing on another planet as it does on Earth are large, then their results will be presented in a way that supports that likelihood,” Turner said. “Our work is not a judgment, but an analysis of existing data that suggests the debate about the existence of life on other planets is framed largely by the prior assumptions of the participants.”

So what do you think?  Are our current expectations of finding life out there in the cosmos based on scientific fact or on mere optimism as suggested by the authors of this study?