Saturn's moon Enceladus has a subsurface ocean that vents the liquid water through long cracks in its icy crust, but as planetary scientists get more familiar with the geysers blasting from the moon, new subtleties are presenting themselves.
Through the analysis of observational data from NASA's Cassini Saturn-orbiting spacecraft and computer modeling, scientists are beginning to realize that when it comes to Enceladus' geysers that erupt from the moon's polar "tiger stripes", there's more than meets the eye.
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"We think most of the observed activity represents curtain eruptions from the ‘tiger stripe' fractures, rather than intermittent geysers along them," said Joseph Spitale, a participating scientist with the Cassini mission at the Planetary Science Institute in Tucson, Ariz. "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."
In short, in new research published today (May 7) in the journal Nature, Spitale's team think that Enceladus' discrete geysers are an illusion.
Called "curtain eruptions", the researchers believe that vapor is being ejected along Enceladus' tiger stripes, which are often wavy fissures. As the vapor is ejected along these wavy features, depending on the angle you're viewing the eruptions from, you will sometimes be looking through the bend or ‘fold' in the curtain of vapor. These folds will make the scattered light from the vapor appear more intense, giving the illusion of being a discreet geyser.
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"The viewing direction plays an important role in where the phantom jets appear," said Spitale. "If you rotated your perspective around Enceladus' south pole, such jets would seem to appear and disappear."
Curtain eruptions occur on Earth in regions of volcanic activity - such as Hawaii, Iceland and the Galapagos Islands. Molten rock can erupt from long fissures, often creating impressive curtains of fire.
"Our understanding of Enceladus continues to evolve, and we've come to expect surprises along the way," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California, who was not involved in the study. "This little ice world is becoming more exciting, not less, as we tease out new details about its subsurface ocean and astonishing geophysical activity."