PULLMAN, Wash., Nov. 21 (UPI) -- An international research group, including U.S. scientists, has proposed the first system for assessing the odds of life on other worlds.
Many scientists believe our own planet serves as the best model of conditions best suited to the existence of life on other worlds, and while there's a certain logic in seeking life in the same sort of conditions in which you already know it to be successful, some researches say that kind of thinking may be limiting.
Dirk Schulze-Makuch, an astrobiologist at Washington State University, and his international colleagues say the search for life on other planets is really driven by two questions.
"The first question is whether Earth-like conditions can be found on other worlds, since we know empirically that those conditions could harbor life," Schulze-Makuch said. "The second question is whether conditions exist on exoplanets that suggest the possibility of other forms of life, whether known to us or not."
Schulze-Makuch and his co-authors -- an international working group representing NASA, SETI, the German Aerospace Center and four universities --propose a new system for classifying exoplanets using two indices, a Washington State release said Monday.
The first is an Earth Similarity Index for categorizing a planet's more Earth-like features. The second has been dubbed a Planetary Habitability Index for describing a variety of chemical and physical parameters that are theoretically conducive to life in more extreme, less Earth-like conditions.
"Habitability in a wider sense is not necessarily restricted to water as a solvent or to a planet circling a star," the researcher group said. "For example, the hydrocarbon lakes on Titan could host a different form of life."
Failure to take such possibilities into account is to is to risk overlooking potentially habitable worlds by using overly restrictive assumptions, they said.