Thinning Margins

Two More Habitable Zones Expand the Case for Design

If you've ever visited the Dead Sea (1,412 feet below sea level) or climbed any high mountain (15,000 feet or more above sea level), you know how altitude affects breathing. Our lungs are incredibly robust, providing the highest conceivable respiratory efficiency for advanced, high-metabolism life.1 Their efficient operation, however, is possible only if the atmospheric pressure falls within a certain range.2 If Earth's air pressure were three times greater or lesser than it is at sea level, respiration would be impossible for advanced, high-metabolism organisms.

A just-right atmospheric pressure belongs to a long list of requirements for the existence of advanced life. A recent paper published by five planetary...