NASA's SDO Sees Two Coronal Holes (image) NASA/Goddard Space Flight Center Share Print E-Mail Caption This image from NASA's Solar Dynamics Observatory on March 16, 2015, shows two dark spots, called coronal holes. The lower coronal hole was one of the biggest observed in decades. Credit NASA/SDO Usage Restrictions None Share Print E-Mail 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.