Images sent back by Cassini (left) show a correspondence with the team's own simulations (right). Credit: NASA/JPL-Caltech/Space Science Institute/Planetary Science Institut
Jets of material erupting from Saturn’s moon Enceladus could be optical illusions caused by fractures in its surface.
NASA’s Cassini mission has captured images of the eruptions and fed the data back to Earth, where scientists have created simulations to determine exactly what they are.
They found that the eruptions of icy particles emanating from Enceladus’s south polar region are better defined as curtain eruptions along the length of fractures in the moon’s jagged surface, rather than the discrete jets identified in earlier studies.
A video showing the simulations is availablehere.
Curtain eruptions occur on Earth when molten rock or magma spurts out of a deep fracture.
They can be seen in places of volcanic activity like Hawaii, Iceland and the Galapagos Islands.
The study was led by Joseph Spitale, a participating scientist on the Cassini mission at the Planetary Science Institute in Tucson, Arizona.
"We think most of the observed activity represents curtain eruptions from the 'tiger stripe' fractures, rather than intermittent geysers along them," he says.
"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."
Observing a faint background glow in most of the images, the team decided the brightest eruptions were superimposed intermittently upon the background structure.
These episodes of brightness appeared in places where the viewer was looking through a fold in the curtain.
The folds are a result of the fractures in Enceladus’s surface being more wavy than straight.
Jets in the simulated images then corresponded with the spacecraft data, giving credence to the theory that they are nothing more than an illusion.
"The viewing direction plays an important role in where the phantom jets appear.
If you rotated your perspective around Enceladus' south pole, such jets would seem to appear and disappear,” Spitale says.