Explanation for formation of abundant features on Europa bodes well for search for extraterrestrial life


Explanation for formation of abundant features on Europa bodes well for search for extraterrestrial life

Press release from: Stanford University
Posted: Monday May 9th 2022

Europa is a prime candidate for life in our solar system, and its deep saltwater ocean has captivated scientists for decades. But it’s surrounded by an icy shell that could be miles to tens of miles thick, making it a daunting prospect. Now, growing evidence reveals that the ice shell may be less of a barrier than a dynamic system – and a site of potential habitability in its own right.

Ice-penetrating radar observations that captured the formation of a “double ridge” feature in Greenland suggest that Europe’s ice shell may have an abundance of water pockets below similar features that are common to the surface. The findings, which appear in Nature Communications April 19, may be compelling for detecting potentially habitable environments outside the Jovian moon.

“Because it’s closer to the surface, where you get interesting chemicals from space, other moons and volcanoes on Io, it’s possible that life will have a hit if there are pockets of water in the shell,” said the study’s lead author. Dustin Schröderassociate professor of geophysics at Stanford University School of Earth, Energy and Environmental Sciences (Stanford Land). “If the mechanism we see in Greenland is the way these things happen on Europa, that suggests there’s water everywhere.”

A terrestrial analogue

On Earth, researchers are analyzing the polar regions using airborne geophysical instruments to understand how the growth and retreat of ice caps could impact sea level rise. study is on land, where ice sheet outflow is subject to complex hydrology — such as dynamic subglacial lakes, surface melt ponds, and seasonal drainage conduits — that contribute to uncertainty in predictions from sea level.

Because an Earth’s subsoil is so different from the ocean of liquid water below the surface of Europa, the study co-authors were surprised when, during a lab group presentation on Europa , they noticed that the formations that streaked the icy moon looked extremely like a minor feature. on the surface of the Greenland Ice Sheet – an ice sheet that the group studied in detail.

“We were working on something totally different related to climate change and its impact on the surface of Greenland when we saw these tiny double ridges – and we could see the ridges change from ‘unformed’ to ‘formed'”, Schroeder said. .

Upon closer examination, they discovered that the “M”-shaped ridge in Greenland, known as the double ridge, may be a miniature version of Europe’s most prominent feature.

Prominent and widespread

The double ridges over Europa appear as dramatic indentations in the moon’s icy surface, with ridges reaching nearly 1,000 feet, separated by valleys about half a mile wide. Scientists have known about the features since the moon’s surface was photographed by the Galileo spacecraft in the 1990s, but have been unable to devise a definitive explanation for how they formed.

Through analyzes of surface elevation and ice-penetrating radar data collected from 2015 to 2017 by NASA’s Operation IceBridge, researchers have revealed how Northwestern Greenland’s Double Ridge came about. when the ice fractured around a pocket of pressurized liquid water that was refreezing inside the ice sheet, causing two peaks to rise in the distinct shape.

“In Greenland, this double ridge formed where water from surface lakes and streams frequently flows to the surface and freezes again,” said study lead author Riley. Culberg, a graduate student in electrical engineering at Stanford. “One way that similar shallow pockets of water could form on Europa could be that water from the subterranean ocean is forced into the ice shell by fractures – and this would suggest that there could be an amount reasonable exchanges inside the ice shell.”

Snowball complexity

Rather than behaving like an inert block of ice, Europa’s shell appears to undergo a variety of geological and hydrological processes – an idea supported by this study and others, including water plume proof which burst to the surface. A dynamic ice shell supports habitability as it facilitates the exchange between the subterranean ocean and nutrients from neighboring celestial bodies accumulated on the surface.

“People have been studying these double ridges for over 20 years now, but this is the first time we’ve been able to observe something similar on Earth and see nature working its magic,” the co-author said. study, Gregor Steinbrügge, a planetary scientist. at NASA’s Jet Propulsion Laboratory (JPL) who began work on the project as a postdoctoral researcher at Stanford. “We are taking a much bigger step in the direction of understanding the processes that really dominate the physics and dynamics of the ice shell of Europa.”

The co-authors said their explanation of how the shape of the double ridges is so complex that they could not have devised it without the analogue on Earth.

“The mechanism we propose in this paper would have been almost too bold and complicated to propose without seeing it happen in Greenland,” Schroeder said.

The results equip researchers with a radar signature to quickly detect this process of double ridge formation using ice-penetrating radar, which is among the instruments currently planned to explore Europa from space.

“We’re another hypothesis on top of many – we just have the advantage that our hypothesis has a few observations of a similar feature forming on Earth to back it up,” Culberg said. “It opens up all these new possibilities for a very exciting discovery.”

Schroeder is also a faculty member of the Human-Centered Artificial Intelligence (HAI) Instituteassociate professor, by courtesy, of electrical engineering and center scholar, by courtesy, at the Stanford Woods Institute for the Environment.

This research was supported by a National Defense Science and Engineering Graduate Fellowship and, in part, NASA grant NNX16AJ95G and NSF grant 1745137.

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