Astronomy Picture of the Day . ... Galileo's First Color Image of Io . ... The blue color of the nebula nearest the bright stars is caused by reflection off interstellar dust. ... This picture of Saturn could not have been taken from Earth. No Earth based picture could possibly view the night side of Saturn and the corresponding shadow cast across Saturn's rings. ... The above artistic portrait of Saturn depicts how it might look from Titan, Saturn's largest moon. ... M81 in True Color . ...