Seemingly painted onto the surface of Saturn's moon Tethys are streaks the color of blood. How these red streaks materialized onto the exterior of Tethys is something scientists have yet to uncover.
Fortunately, a close Saturn flyby in November allowed experts to further examine the otherworldly artwork and look into Tethys' smudges. What they are discovering is extremely baffling, scientists said.
Paul Schenk, a Lunar and Planetary Institute scientist, presented his observations concerning Tethys' red streaks at the annual meeting of the American Geophysical Union on Tuesday.
"You don't see any trace of scarps or ridges or depressions of any kind," said Schenk, noting that there were no obvious topographical formations related to the streaks. At the very least, he said the formations may not even be big enough for Cassini to see using its current resolution.
Some of Tethys' craters seem to contain strange and dark material, but Schenk was uncertain what the material was, how it got there, or whether it really is associated with the red streaks or not.
Schenk said it appears as if someone had just painted the moon with red. "If you didn't have the color, you wouldn't know they were there," he said.
The nearest clue to this baffling mystery was the location of the red streaks.
To find out where the streaks come from, Schenk plotted their locations on Tethys. He mapped the lines onto the surface, and found a pattern that suggests the moon is being deformed or squeezed by some kind of global stress. These could be caused by a shifting orbit, irregular rotation or the migration of the moon's poles, he said.
However, simulations of the processes described above do not produce landforms that quite match up with the location of the streaks.
Still, Schenk said the streaks are relatively young. Dust from Saturn's E ring and some of the charged particles from space would erase the streaks, but somehow, they still remain there.
Schenk also observed that the red streaks are drawn on top of Tethys' largest crater Odysseus. This could mean that the crater came first. Scientists do not know how old Odysseus is, but Schenk said the crater could have been formed more than 2 billion years ago.
In the end, Schenk said his best guess would be that the red streaks are connected to fractures that Cassini cannot see. Those invisible fractures may be continuously forming, or may have been reactivated lately. The latter may have exposed material that is unlike water ice.
Cassini's Saturn exploration is nearing its end, but scientists are hoping to solve this baffling mystery soon.
