What Are These Strange Scarlet Streaks Spotted on Tethys?

Resembling what the skin on my arms looks like after giving my cat a bath, the surface of Saturn’s moon Tethys is seen above in an extended-color composite from NASA’s Cassini spacecraft showing strange long red streaks. They stretch for long distances across the moon’s surface following the rugged terrain, continuing unbroken over hills and down into craters… and their cause isn’t yet known.

According to a NASA news release, “The origin of the features and their reddish color is currently 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. The streaks could also be associated with features like fractures that are below the resolution of the available images.”

The images were taken by Cassini during a flyby of the 660-mile-wide (1,062 km) Tethys on April 11, 2015 at a resolution of about 2,300 feet (700 meters) per pixel. They were acquired in visible green, infrared,  and ultraviolet light wavelengths and so the composite image reveals colors our eyes can’t directly perceive. The combination of this and the solar illumination needed to image this particular area as the spacecraft passed by are why these features haven’t been seen so well until now.

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

Extended color mosaic of Tethys from Cassini images acquired on April 11, 2015. The region where the streaks are is outlined. Click for original hi-res version. (NASA/JPL-Caltech/SSI)
Extended color mosaic of Tethys from Cassini images acquired on April 11, 2015. The region where the streaks are is outlined. Click for original hi-res version. (NASA/JPL-Caltech/SSI)

While the nature of Tethys’ streaks isn’t understood, the observations do indicate a relatively young age compared to the surrounding surface.

“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 Cassini imaging scientist at Cornell University in Ithaca. “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.”

Reprocessed Galileo image of Europa's frozen surface by Ted Stryk (NASA/JPL/Ted Stryk)
Reprocessed Galileo image of Europa’s streaked surface by Ted Stryk (NASA/JPL/Ted Stryk)

Could these arcs be signs of an underground ocean or reservoir of briny liquid, like Enceladus’ tiger stripes (aka sulcae) or the streaks that crisscross Europa’s ice? Or are they the results of infalling material from one of Saturn’s other moons? More observations with Cassini, now in its eleventh year in orbit at Saturn, are being planned to “study the streaks.”

“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,” said Linda Spilker, Cassini project scientist at JPL.

Source: NASA JPL

15 Replies to “What Are These Strange Scarlet Streaks Spotted on Tethys?”

  1. Well the fact that they are loosely aligned looks like geyser refuse landing back down on the moon…

  2. there’s one seeming to emerge from a crater near bottom left and is longer and wider than those at the top.

    1. I don’t know what do you mean, but I can see a fairly big streak at bottom right, where it’s getting darker, like 4 o’clock, don’t even have to click for a bigger pic.

      1. right – zoom in a bit and trace it back to the left. Seems to start in one particular crater

  3. My best guess would be the moon flew through the tail of a comet breaking up on it’s way into Saturn. The arc’s are a straight line from a different perspective.

    1. They do appear concentric, but with no obvious crater in their center on this side in the image. But what about them cutting through craters large and small? Doesn’t that tell us they are recent? A huge crater like Odysseus should not be recent. Maybe it caused a long lasting activity of some kind.

    2. I don’t have the complete picture, but are these lines definitely coming from the center of the impact crater? Or are they skewed to some angle from the impact crater? Do they extend into the impact crater? Are they the same relative age of the impact crater? They look more like relatively new feature of debris going over the tops of other impact craters rather than from an old massive crater that most likely formed during the young solar system.

    3. To me it looks like Obysseus is right off the right hand horizon next to these red streaks at the top (but far away and no radially linear from Obysseus from the one near botton center.)

      1. HeadAroundU, if so, she’s got to work on it, for another few billion years. She looks a bit like a death star (and the 1st star wars movie was produced before Voyager was even launched, how did they guess that several moons look like that?)

  4. It is interesting to try and reconstruct how the pink stuff interacted with the surface shapes when it landed. It does not seem to have disturbed any of the crater features, which suggests that this is a light dusting of pink stuff, rather than a crack coming upwards. At the top left there is a crater which seems to have a uniform line through it without any significant shadowing. This would suggest that the pink stuff was coming straight down.

    I can think of a number of ways of making a conical shower of debris, but the angle of the cone is often about 45 degrees. I can not come up with a sensible way of making a very pointy cone of debris like this. So, let’s abandon cones. Suppose we had something like a crumbling bit of a comet that gave lines of debris in space, like Shoemaker-Levy but much smaller. These streaks would arrive at Tethys over a period of an hour or so, and Tethys rotates once ever 1.8 days, so this would give you an arc in the rotation direction if the lines of debris were straight. They probably are not quite straight, so the lines on Tethys are curved.

    This theory only works if the lines are roughly aligned with the rotation of Tethys.

  5. Crayon marker comes closest,
    so something orbiting (captured by) Saturnus and disintegrated (impacted) leaving telltale marks on the surface of Tethys.

    The original orbit might be easily traced back.
    – At least inside the orbit of Tethys
    – Probably eliptical
    – 80% orbit length of Tethis?
    – Shifted orbit at least twice

  6. Was a part of Tethys always yellow? The second high-res photo seems like it was taken in a studio with a subdued yellow light shining on it from the left.

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