Atmospheric Features on Neptune (IMAGE) University of Arizona Caption In this image, the colors and contrasts were modified to make the planet’s atmospheric features stand out. The winds in Neptune's atmosphere can reach the speed of sound or more. Neptune's Great Dark Spot stands out as the most prominent feature on the left. The fainter Dark Spot 2 and the South Polar Feature are locked to the planet's rotation, which allowed Karkoschka to precisely determine how long a day lasts on Neptune. Credit Erich Karkoschka Usage Restrictions Usage only granted in conjunction with reporting/posting of this news release. Credit must be stated as indicated. 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.