(IMAGE) Helmholtz Centre for Environmental Research - UFZ Caption A large fairy circle with a hardened top-soil layer that prevents the growth of grass is shown. Australian fairy circles have mean diameters of 4 meters but some may exceed 7 meters. Credit Stephan Getzin Usage Restrictions None License Licensed content 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.