Europa: Ice Line . ... Galileo Project , NASA Explanation: This bright white swath cutting across the surface of icy Jovian moon Europa is known as Agenor Linea . In all about 1000 kilometers long and 5 kilometers wide, only a section is pictured here as part of a combined color and black and white image based on data from the Galileo spacecraft. Most linear features on Europa are dark in color but Agenor Linea is uniquely bright for unknown reasons. ... NASA Official: Jay Norris. ...