In many fields of science, the imagination is only limited by the language that can explain it.
As we discovered nearly a year ago, forms of life could exist that play by rules beyond our base of knowledge.
Scientists know that it's likely that they will discover many more planets orbiting distant stars. They also know that researchers are most likely to focus on those that exhibit Earth-like conditions, in an attempt to find life in another part of the universe.
But what if alien life can exist in conditions drastically unlike those of Earth? Will scientists mistakenly overlook them?
Driven by this fear -- and the admission that searching for Earth-like conditions as a precondition for life is a basic but incomplete strategy for finding it -- an international team of researchers from NASA, SETI and several universities are working to develop a classification system that includes chemical and physical parameters that are theoretically conducive to life, even if they result in decidedly un-Earth-like conditions.
Washington State University astrobiologist Dirk Schulze-Makuch, University of Puerto Rico modeling expert Abel Mendez and seven more colleagues have developed two different indices -- an Earth Similarity Index that categorizes a planet's more Earth-like features, and a Planetary Habitability Index that includes theoretical parameters -- that they say can help researchers more easily find patterns in large and complex datasets.
It's the first attempt by scientists to categorize the potential of exoplanets and exomoons to harbor life, and should prevent Earth-bound researchers from overlooking conditions that are, ahem, alien to them in their search for life.
Their work will be published in the December issue of the journal Astrobiology.