Intense tectonism is evident on many outer solar system satellites — such as Ganymede, Europa, and Enceladus — with some surface regions showing ridge-and-trough structures which have characteristics suggestive of normal faulting. In some cases, topographic lows between subparallel ridges are sites of smooth material displaying few craters. In new research, scientists from the University of Arizona and NASA’s Jet Propulsion Laboratory developed and tested the hypothesis that some smooth materials on the icy satellites formed through degradation of fault blocks by seismically triggered landslides.
On the surfaces of icy moons such as Europa, Ganymede, and Enceladus, it’s common to see steep ridges surrounded by relatively flat, smooth areas.
Planetary scientists have theorized that these spots result from liquid that flows out of icy volcanoes.
But how that process works when the surface temperatures are so cold and inhospitable to fluids has remained a mystery.
A simple explanation outlined in the study doesn’t involve liquid on the surface.
University of Arizona graduate student Mackenzie Mills and colleagues measured the dimensions of the steep ridges, which are believed to be tectonic fault scarps (like those on Earth) — steep slopes caused when the surface breaks along a fault line and one side drops.
By applying the measurements to seismic models, the researchers estimated the power of past moonquakes and found they could be strong enough to lift debris that then falls downhill, where it spreads out, smoothing the landscape.
“We found the surface shaking from moonquakes would be enough to cause surface material to rush downhill in landslides,” Mills said.
“We’ve estimated the size of moonquakes and how big the landslides could be.”
“This helps us understand how landslides might be shaping moon surfaces over time.”
NASA’s upcoming Europa Clipper mission, bound for Jupiter’s moon Europa in 2024, will give the research a…
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