Porco notes that the "spreading" discovery is yet another sign that Enceladus has a level of geologic activity that seems to demand the presence of liquid water below the south polar terrain.
"We're growing more and more confident that it is virtually impossible to explain what we see on Enceladus without liquid water somewhere in its interior," she said.
The strange dome straddling what appears to be the oldest of the tiger stripes may be an important clue to what eventually set the jets in motion, Helfenstein said.
If it is the top of an ancient diapir, the dome may mark a place where warm ice or even liquid water flowed upward from deeper beneath Enceladus's surface.
Perhaps, he added, that process might have been initiated by an impact on the surface. A comet impact, for example, may have sent shock waves rebounding from the moon's core, creating surface fractures and a warm region below.
Once heated, more energy could have been generated as tides driven by Saturn's pull flexed the 300-mile-wide (480-kilometer-wide) moon and caused the fractured blocks of crust to rub against each other.
Such a process could have powered not only the jets but may have produced enough heat to cause the crust to begin spreading.
The new announcement, however, is far from the final word on Enceladus and its epic jets.
"It's an hypothesis," Helfenstein said. "We have to think very carefully about how to test it, or if it's even testable."
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