A new study based on data from NASA's Cassini spacecraft suggests that the Saturnian moon Enceladus tipped onto its side after an asteroid collision led to the formation of the satellite's famous tiger-striped terrain. The fractures in Enceladus' south polar region, now affectionately known as tiger stripes, were first discovered in 2005, when Cassini spotted colossal plumes of material extending tens of miles from the surface of the icy world.
Since their discovery, the geysers have been the focus of exhaustive studies by the veteran probe, the data from which has allowed scientists to construct theories on what is driving the activity.
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It is now thought that the material cast out from the tiger-stripe vents is drawn from a vast subsurface ocean that exists beneath a thick crust of ice. It is possible that the geysers are powered by tidal forces created by interactions between nearby Saturn's gravity and the moon's interior structure. The turbulence created by the resultant tidal pumping heats the material in the vents, causing it to erupt in geyser form, and creating an environment that could theoretically house extra-terrestrial life.
A mosaic of Enceladus' tiger-stripe geysers, comprised from images taken by the Cassini spacecraft during a 2009 flyby (Credit: NASA/JPL/Space Science Institute)
A new study carried out by the Cassini science team is now suggesting that the cryovolcanic feature may have formed near Enceladus' original equator, before a dramatic shift in the moon's polar axis toppled the frigid world, creating the south polar region we see today.
Cassini scientists identified the potential remains of Enceledus' original equator in the form of a chain of basins that they believe once ran across the belt of the planet. The team also discovered two large depressions that would correspond with the fossil equator to form ancient polar regions.
According to the paper, now published in the journal Icarus, Enceladus rolled onto its side following the formation of the tiger-stripe region, possibly in the aftermath of a powerful asteroid impact. Regardless of how the vents came to form, the Cassini team believes that their creation triggered a redistribution of mass that destabilized the moon's rotation for roughly a million years.
Annotated NASA image displaying the possible location of Enceladus' origional south pole vs its current one (Credit: NASA/JPL-Caltech/Space Science Institute/Cornell University)
By the time Enceladus had settled, it had shifted a full 55 degrees of latitude onto its side, placing the active tiger-stripe terrain at the newly created south pole.
The research would help to explain why the terrain region around the vents is so youthful (in geological terms at least), when compared to the heavily cratered north pole. It would also cover why the south pole has geysers when the north does not.
Source: NASAView gallery - 3 images