New images taken fromNASA's Cassini spacecraft appear to show unusual redish arcs markingthe surface of the Saturn's icy moon Tethys. The strange featurescover significant stretches of the moon's surface, and have leftastronomers baffled as to their origins.
First discovered in1684 by Italian mathematician and astronomer Giovanni DomenicoCassini, the icy moon Tethys orbits Saturn at a distance of roughly295,000 km (183,000 mi), and is believed to consist predominantlyof water ice.
The newest shots of theenigmatic moon were created by combining a number of images takenusing clear, green, infrared and violet spectral filters fromCassini's onboard camera. The resulting views emphasize a series ofstrange red arcs, some of which stretch for several hundred milesacross the barren landscape, dulling the moon's otherwise highlyreflective surface.
The images captured by Cassini inApril are the first to clearly feature large sections of Tethys'northern hemisphere, which has become better lit as the regiontransitioned into a "summer phase". Judging by the way thatthe arcs seem to traverse older surface features, such as impactcraters, astronomers are working on the assumption that the arcs arerelatively young.
Another fascinatingaspect of the arcs is their reddish tinge, as this hue is extremelyrare amongst Saturn and her 53 confirmed satellites. There iscurrently no consensus as to the origins of the arcs, however leadingtheories attribute their existence to chemical impurities in the icysurface of the moon, or possibly a bi-product of outgassing, similarto the activity observed to be taking place on the comet67P/Churyumov–Gerasimenko.
Should the marks turnout to be a shallow stain on the surface of the moon, it is expectedthat exposure to the harsh space environment should diminish theirpresence in a fairly short period of time.
"After 11 years inorbit, Cassini continues to make surprising discoveries," statesLinda Spilker, Cassini project scientist at NASA's Jet PropulsionLaboratory. "We are planning an even closer look at one of theTethys red arcs in November to see if we can tease out the source andcomposition of these unusual markings."
Source: NASA JetPropulsion Laboratory
