for National Geographic News
Unusual geysers on the south pole of Saturn's moon Enceladus have been drawing the attention of astronomers searching for liquid water—and maybe life—on other worlds.
But new research on the moon's geologic features suggests water need not be involved, and may put hopes for life on ice.
The icy pole boasts ridges, vents, and other formations that emit the geysers, and scientists have recorded heat transfer at the pole's surface.
Based on these observations, some experts have theorized that the moon has a warm, shifting interior similar to Earth's.
Our planet's hot insides are what power geysers like the famous Old Faithful in Yellowstone National Park.
On Enceledus, scientists think, the geysers form when heat from deep inside melts water ice just below the surface, forming shallow pockets of liquid water.
When tectonic movements crack the ice cap, liquid water bursts forth and quickly refreezes, creating the geysers.
Now a new model "shows that it's possible to put these three observational elements"—geysers, geologic features, and heat flow—"into one unified explanation without the need for water," said study co-author Gustavo Gioia of the University of Illinois at Urbana-Champaign.
Gioia and colleagues suggest that the ridges where the plumes emerge were formed from a single heating event that expanded and cracked the surface.
A shell made of icy compounds is exposed by the ridges, causing the compounds to decompress and absorb heat. The compounds then explosively split into smaller parts and send ice crystals and gases skyward.
"That doesn't mean that there is no [liquid] water," Gioia cautioned. "It just means that you can explain the whole thing without there being water there."
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