Earthly comparison hints at shallow liquid water on Jupiter’s moon – The Echo

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Similarities between Europa and Greenland ice sheets provide clues.

Europa’s icy crust holds new surprises for scientists. Credit: NASA/JPL/University of Arizona.

Researchers have revealed new insight into the geology of Jupiter’s moon Europa, described by NASA as one of the most promising locations in our solar system for present-day extraterrestrial life.

Scientists strongly suspect that Europa, one of an estimated 79 moons orbiting the planet Jupiter, harbors liquid water in the form of a large saltwater ocean beneath a frozen icy crust. Europa’s ice “shell” is estimated to be 20-30 kilometers thick.

In a paper published today in NatureCommunicationsa research team led by Riley Culberg of Stanford University, US, presents evidence that shallow liquid water also exists much closer to Europa’s surface, within the ice shell.

Europa’s ice shell is covered in landforms called “double ridges” – consisting of two ridges of ice that are nearly symmetrical on either side of a shallow trough – up to hundreds of kilometers long.

Europa’s double ridges. Left: an image of a double ridge taken by the Solid State Imaging (SSI) system on NASA’s Galileo spacecraft. Upper right: a computer-generated 3D model of the double ridge structure. Lower right: a colored version of the model. The red tones indicate that the crests of the ridge system reach elevations of nearly 1000 feet (more than 300 meters) above the surrounding furrowed plains (blue and purple tones). The two ridges are separated by a valley about a mile (1.5 kilometers) wide. Credit: NASA/JPL/DPR.

In the new study, the researchers investigated a double ridge found on Earth in the ice sheet over northwest Greenland. The double ridge is very similar in shape to those found on Europa.

Using surface elevation and radar sounding data, the team found that the Greenland double ridge was probably formed by shallow liquid water within the ice sheet gradually refreezing, becoming pressurized and eventually fracturing the ice.

This finding implies that a similar mechanism might cause the double ridges on Europa as well – although there are some differences. In Greenland, the regions of shallow liquid water are formed by drainage of meltwater from the surface. On Europa, the liquid water might instead be injected from below, originating from the moon’s subsurface ocean.

Infographic explaining current knowledge of Europa’s likely ocean. Credit: NASA/JPL-Caltech.

The study suggests that shallow liquid water may be more important to shaping Europa’s surface than previously recognised.

“If this mechanism controls double ridge formation at Europa, the ubiquity of double ridges on the surface implies that liquid water is and has been a pervasive feature within the brittle lid of the ice shell,” Culberg and colleagues write.

With NASA’s Europa Clipper mission scheduled to be launched in October 2024, we’ll no doubt learn much more in the coming decades about the geology of this intriguing moon – and its potential to harbor life.


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