Composite of C/2013 A1 (image) NASA/Goddard Space Flight Center Share Print E-Mail Caption This composite of C/2013 A1 (Siding Spring) merges Swift UVOT images taken between May 27 and 29, 2014. Sunlight reflected from the comet's dust, which produces most of the light in this image, appears yellow; violet shows ultraviolet light produced by hydroxyl (OH), a molecular fragment of water. Credit NASA/Swift/D. Bodewits (UMD), DSS 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.