With all of the attention Pluto and its moons have garnered lately, it's easy to forget that there are other spacecraft out there examining other parts of our solar system. For example, NASA's Saturn-snooping Cassini spacecraft captured an image that shows a set of intriguing red marks streaking across the icy surface of the ringed planet's moon Tethys.
"Like graffiti sprayed by an unknown artist, unexplained arc-shaped, reddish streaks are visible on the surface of Saturn's icy moon Tethys," NASA reported Wednesday.
The red marks showed up in new, color-enhanced images stitched together from Cassini, which has been orbiting Saturn since 2004.
Released today, the original images were obtained in April 2015 and allowed NASA researchers to see a part of Tethys -- one of Saturn's 53 named moons -- that has previously been a little murky.
"As the Saturn system moved into its northern hemisphere summer over the past few years, northern latitudes have become increasingly well illuminated. As a result, the arcs have become clearly visible for the first time," said the space agency.
As of now, Cassini's scientists don't know what caused the arcs, but they do have a few theories. The marks might be from ice with chemical impurities, gas escaping from the center of the moon or fractures in its surface. One thing they are sure of is that the marks are relatively new.
"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." said Paul Helfenstein, a scientist at Cornell University working on the Cassini imaging team. "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."
While NASA didn't release the precise size of the arcs, the organization did say that they measure "only a few miles (or kilometers) wide but several hundred miles (or kilometers) long."
The space agency plans to take a closer look at one of the red streaks in November to delve deeper into the mystery of the marks.