Phantom Jets at Enceladus May Be an Optical Illusion

[iframe width="560" height="315" src="" frameborder="0" allowfullscreen] Jets or curtains? That depends on your point of view.New research on the geyser-like eruptions from Saturn's moon...

Enceladus curtain jets

[iframe width="560" height="315" src="" frameborder="0" allowfullscreen]

Jets or curtains? That depends on your point of view. New research on the geyser-like eruptions from Saturn's moon Enceladus reveal that they may be aurora-like curtains erupting from long sinuous cracks instead of distinct, individual jets. Every second, the 313-mile-diameter moon spews 440 pounds (200 kg) of water vapor, salt crystals and ice particles. Some falls as "snow" while the rest helps to grow Saturn's E-ring .

Enceladus jets curtains NASA JPL
Phantom jets in simulated images produced by the scientists line up nicely with some of the features in real images from NASA's Cassini spacecraft that appear to be discrete columns of spray. Credit: NASA/JPL/SSI/PSI

"We think most of the observed activity represents curtain eruptions from the 'tiger stripe' fractures, rather than intermittent geysers along them," said Joseph Spitale, lead author of the study and a participating scientist on the Cassini mission. "Some prominent jets likely are what they appear to be, but most of the activity seen in the images can be explained without discrete jets."


The curvy cracks in Enceladus' icy surface nicknamed "tiger stripes" that are responsible for the diffuse, curtain-like sprays of material from the moon's interior. It's thought that Enceladus harbors a sub-surface ocean around 6 miles (10 km) deep. Credit: NASA/JPL-Caltech

Watching the video will make the illusion of jets clear. You'll see them materialize when looking through folds in curtains of material erupting from the stripes. A bright ray appears when the material in both the foreground and background aligns or stacks up. As our viewing geometry changes, we see the hazy emissions from the side (instead of head on), and most of the rays seem to magically disappear. Folds exist because the fractures in Enceladus' surface are more wavy than perfectly straight.

Curtain of fire eruption at Mauna Loa. Credit: USGS

The correspondence between simulation and spacecraft data suggests that the jet-like structure is an illusion. On Earth, curtain eruptions occur where magma gushes out of a deep fracture. These eruptions, which often create spectacular curtains of fire like the one at left in Hawaii.

This new perspective shows how continued study, even of a little icy ball nearly a billion miles from home, brings refinements in our understanding of its nature, a neat analogy to processes seen right here on Earth and of course, surprises.

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