Habitable zones (IMAGE) University of California - Riverside Caption A habitable zone, shown in green here, is defined as the region around a star where liquid water, an essential ingredient for life as we know it, could potentially be present. Credit NASA/JPL-Caltech Usage Restrictions No restrictions. License Public Domain Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.