Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

Unusual red arcs spotted on Saturn’s icy moon Tethys

Narrow, curved red lines on Tethys’ surface are among the most unusual color features on Saturn’s moons to be revealed by Cassini’s cameras.
RELATED TOPICS: SOLAR SYSTEM | TETHYS | SATURN | CASSINI
Red arcs on Tethys
Unusual arc-shaped, reddish streaks cut across the surface of Saturn's ice-rich moon Tethys in this enhanced-color mosaic. The red streaks are narrow, curved lines on the moon's surface, only a few miles wide but several hundred miles long.
NASA/JPL-Caltech/Space Science Institute
Like graffiti sprayed by an unknown artist, unexplained arc-shaped, reddish streaks are visible on the surface of Saturn’s icy moon Tethys in new enhanced-color images from NASA’s Cassini spacecraft.

The red arcs are narrow, curved lines on the moon’s surface and are among the most unusual color features on Saturn’s moons to be revealed by Cassini’s cameras.

Images taken using clear, green, infrared, and ultraviolet spectral filters were combined to create the enhanced-color views, which highlight subtle color differences across the icy moon’s surface at wavelengths not visible to human eyes.

A few of the red arcs can be seen faintly in observations made earlier in the Cassini mission, which has been in orbit at Saturn since 2004. But the color images for this observation, obtained in April 2015, are the first to show large northern areas of Tethys under the illumination and viewing conditions necessary to see the arcs clearly. 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.

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

The origin of the features and their reddish color is a mystery to Cassini scientists. Possibilities being studied include ideas that the reddish material is exposed ice with chemical impurities, or the result of outgassing from inside Tethys. They could also be associated with features like fractures that are below the resolution of the available images.

Except for a few small craters on Saturn’s moon Dione, reddish-tinted features are rare on other moons of Saturn. Many reddish features do occur, however, on the geologically young surface of Jupiter’s moon Europa.

“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 from Cornell University in Ithaca, New York, who helped plan the observations. “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.”

The Cassini team is currently planning follow-up observations of the features at higher resolution later this year.

“After 11 years in orbit, Cassini continues to make surprising discoveries,” said Linda Spilker from NASA’s Jet Propulsion Laboratory in Pasadena, California. “We are planning an even closer look at one of the Tethys red arcs in November to see if we can tease out the source and composition of these unusual markings.”
0

JOIN THE DISCUSSION

Read and share your comments on this article
Comment on this article
Want to leave a comment?
Only registered members of Astronomy.com are allowed to comment on this article. Registration is FREE and only takes a couple minutes.

Login or Register now.
0 comments
ADVERTISEMENT
FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter. View our Privacy Policy.

ADVERTISEMENT
ADVERTISEMENT
Apollo_RightRail
A chronicle of the first steps on the Moon, and what it took to get there.
Find us on Facebook