Astronomy & Space

Icy moonquakes: Surface tremors may cause landslides

According to a new NASA study, the mysteriously smooth terrain on Jupiter and Saturn’s moons may be caused by earthquakes.

It is known that many of the giant planets’ icy moons that orbit them in our solar system’s farthest regions are active geologically. Because of their extremely strong gravity, Jupiter and Saturn stretch and pull the bodies that are in orbit around them, resulting in moonquakes that can crack the surfaces and crusts of the moons. For the first time, new research demonstrates how these quakes may cause landslides that create remarkably smooth terrain.

The study, which was published in Icarus, sheds new light on the evolution of icy moon surfaces and textures by highlighting the link between quakes and landslides.

It is common for the surfaces of icy moons like Europa, Ganymede, and Enceladus to have steep ridges that are surrounded by areas that are relatively flat and smooth. These spots may be the result of liquid flowing from icy volcanoes, according to scientists. However, it is still unknown how that process operates when the surface temperatures are so low and inhospitable to fluids.

The study offers a straightforward explanation that does not involve liquid on the surface. Scientists measured the length and width of the steep ridges, which they believe to be tectonic fault scarps similar to those on Earth, which formed when one side of the surface broke along a fault line. They estimated the power of previous moonquakes by putting the measurements into seismic models. They found that these moonquakes could lift debris that fell downhill and spread it out, smoothing the landscape.

“We discovered that the surface shaking caused by moonquakes would be sufficient to result in landslides in which surface material rushed downhill. We’ve assessed the size of moonquakes and how huge the avalanches could be,” said lead creator Mackenzie Factories, an alumni understudy at the College of Arizona in Tucson, who led the work during a progression of summer entry-level positions at NASA’s Stream Impetus Research facility in Southern California. “This helps us comprehend how landslides might over time alter moon surfaces.”

 Credit: Icarus (2023). DOI: 10.1016/j.icarus.2023.115534

Robert Pappalardo, co-author and Europa Clipper project scientist at JPL, who oversees the mission, said, “It was surprising to find out more about how powerful moonquakes could be and that it could be simple for them to move debris downslope.”

The modeling results for tectonic activity and quakes on Saturn’s moon Enceladus, which has less than 3% of Europa’s surface area and about 1/650 of Earth’s, were especially surprising. “Pappalardo stated that quakes on tiny Enceladus could be large enough to fling icy debris right off the surface and into space like a wet dog shaking itself off,” Pappalardo said. “This is because that moon has such a small gravity.”

The high-resolution images collected by the Europa Clipper will assist scientists in determining the magnitude of previous moonquakes on Europa. The most recent findings will allow researchers to determine whether and how much ice and other surface materials have been moved by earthquakes. Similar details about Ganymede, Europa’s neighboring Jovian moon, will be provided by images from the ESA’s Jupiter Icy Moons Explorer (JUICE) mission.

According to Pappalardo, “We hope to gain a better understanding of the geological processes that have shaped icy moons over the course of time and to what extent their surfaces may still be active today.”

More information: Mackenzie M. Mills et al, Moonquake-triggered mass wasting processes on icy satellites, Icarus (2023). DOI: 10.1016/j.icarus.2023.115534

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