According to new research, tidal pressures on Saturn’s sixth-biggest moon Enceladus, a planet of interest in the hunt for life beyond Earth, maybe producing continuous icequakes. A deeper knowledge of seismic activity may disclose what lies under the moon’s ice shell and give hints to its ocean’s habitability. Enceladus has a diameter of roughly 500 kilometers and is nearly completely covered in ice.
Despite the fact that the moon is approximately 10 times as far away from the Sun as Earth, and its brilliant surface reflects most sunlight, making it very frigid, scientists have long theorized that the ice encases an underlying liquid ocean. Similar to how Earth’s Moon generates tides on Earth, the moon is likely subjected to tremendous tidal forces generated by Saturn and the planet’s other, larger moons. Inside Enceladus, tidal movements warm the interior, break the surface, and occasionally compress towering geysers of water vapor through prominent cracks known as the tiger stripe fractures.
Tides on Enceladus, like icequakes on Antarctica’s floating ice sheets, may trigger tiny quakes in the ice along the moon’s cracks, according to a new research-based on studies of Antarctic ice shelves.
“Moons like these are places that are exciting because they might have life,” said Kira Olsen, a geophysicist at NASA’s Goddard Space Flight Center. She said that “since life is thought to have first developed in our oceans, liquid oceans under the ice of other worlds could be a good place to search for life.”
Enceladus’ ice shell may potentially shield the water beneath it from radiation, making it more livable. The new discovery was published in the Publication of Geophysical Research: Planets, the American Geophysical Union’s journal for research on the creation and development of planets, moons, and other solar system objects and beyond.
“We have ideas of how thick the ice could be, but we don’t have a direct observation. Studying ice quakes is a way to get at that information,” Olsen said.
Internal Tides –
To understand more about how Enceladus’ tiger cracks could be moving, Olsen and her colleagues looked to Antarctica’s floating ice shelves as the closest Earth parallel for the sorts of activity they were witnessing on Enceladus. They may then utilize their understanding of how specific surface characteristics on Earth cause seismic activity to predict what type of seismic activity is occurring on the moon.
Between 2014 and 2016, the researchers evaluated data acquired by seismometers along the Ross Ice Shelf in Antarctica and compared it to satellite pictures of the area. They were especially interested in two seismometers positioned near major rifts in the ice slab. Seismic activity was linked to stress along these rifts, according to the researchers. On the Ross Ice Shelf, the bulk of icequakes occurred while the rifts were pulling apart, which occurs when the tides are falling.
Although there are no observations of seismic activity on Enceladus, Olsen and her colleagues developed models that compared the sorts of cracks seen on the moon’s surface to those seen on the Ross Ice Shelf.
The highest amount of seismic activity on Enceladus, according to these simulations, is related to the tides. Enceladus’ seismic activity peaks when it is 100 degrees past Saturn’s closest approach during its orbit. At this stage, the ocean beneath the ice behaves like water inside a sloshing balloon. The ice cracks are formed where the balloon would break apart under the most tension.
Even at high-stress periods, the icequakes aren’t enormous along with these fractures. They’re more like tiny snaps and fractures, according to Olsen. While the Cassini probe indicated the moon is geologically active, Mark Panning, a research scientist at NASA’s Jet Propulsion Laboratory who was not involved in the current study, said it’s difficult to say how that translates to seismic activity.
“The study represents a really key way of investigating what seismicity on Enceladus and other tidally activated icy worlds may look like by looking at the best analogs we can find on Earth,” he said.
Any future trips to Enceladus, according to Olsen, should try to put seismometers within 10 kilometers of these cracks to learn more about what’s going on underneath.
“It’s not a quiet out of the way place, but it’s a pretty good place to study,” she said.
More information about the seismic activity might help us figure just how thick Enceladus’ ice crust is. There are currently no plans for expeditions to Enceladus, however, the European Space Agency is preparing the JUICE mission to Europa, one of Jupiter’s ice moons.
Similar research may potentially be done on Titan, Saturn’s biggest moon, which is likewise covered in ice and could hide liquid seas, making it a top candidate for extraterrestrial life, according to Olsen. Titan will be visited by NASA’s Dragonfly mission in 2036.
“This kind of work is one of the best ways to try to get an idea of what behaviors we may see on a planetary body that would be an incredible place to do more science,” Panning said.
