New color images from NASA’s Cassini spacecraft have revealed strange, graffiti-like red-colored streaks on the surface of Saturn's icy moon Tethys. The narrow, arc-shaped lines are said to be among the most unusual color features on the ringed planet’s moons revealed by Cassini’s cameras.

Some of the reddish arcs could be seen faintly in observations made earlier in the Cassini mission. But, according to scientists, the new color images obtained in April, are the first to show large northern areas of Tethys under favorable viewing conditions, thereby displaying the arcs clearly.

“The red arcs really popped out when we saw the new images,” Paul Schenk of the Lunar and Planetary Institute in Houston, and a participating scientist in the Cassini mission, said in a statement. “It's surprising how extensive these features are.”

SaturnmoonTethys An enhanced-color mosaic of Saturn's icy moon Tethys. Photo: NASA/JPL-Caltech/Space Science Institute

According to the scientists, the origin of these features and their reddish color remains a mystery. There are possibilities that the arcs could be exposed ice with chemical impurities, or the result of the release of a gas from inside Tethys, the scientists said, adding that the streaks could also be fractures that are below the resolution of the available images.

Although red-colored features are rare on other moons of Saturn, many such features also occur on the surface of Jupiter's moon Europa, the scientists said.

“The red arcs must be geologically young because they cut across older features like impact craters, but we don't know their age in years,” Paul Helfenstein, a Cassini imaging scientist at Cornell University, Ithaca, in New York, said in the statement. “If the stain is only a thin, colored veneer on the icy soil, exposure to the space environment at Tethys' surface might erase them on relatively short time scales.”