Unusual Lines

Saturn’s moon Dione appears to be getting its tiger on. The world is decorated with long, bright stripes, according to a new study, something astronomers say is unlike anything else they’ve seen in the solar system.After first noticing these stripes, researchers from the Planetary Science Institute and the Smithsonian began trying to figure out where they came from and why they exist.They were able to rule out tectonic origins for the stripes — things like faults. Instead, the bright lines, or “linear virgae” as the researchers call them, were probably caused by material falling from the heavens, study author Emily Marten said in a press release . The stripes’ components could have come from Saturn’s rings, a close-passing comet, or co-orbital moons Helene and Polydeuces, which orbit Saturn along the same path as Dione.To study the stripes, the pair looked at images taken by NASA’s Cassini spacecraft over the period of about a decade and compared them to other linear features observed in our solar system. Saturn’s moon Rhea has features that look somewhat similar, but their distribution is very different than on Dione. The lines on Dione are relatively parallel, but those on Rhea are more randomly oriented, the authors explain.