Potential plumes on Europa could come from water in the crust

According to new research, plumes of water vapor that could be vented into space by Jupiter’s moon Europa could come from within the same ice crust. One model outlines a process for brine, or salt-enriched water, moving inside the moon’s shell and eventually forming pockets of water, even more concentrated with the salt, that could erupt.

Scientists from Europa have seen the possible plumes on Europa as a promising way to investigate the habitability of Jupiter’s icy moon, especially as they offer the opportunity to be sampled directly from spacecraft passing through them. Information on the activity and composition of the ice shell covering Europa’s global inland ocean can help determine whether the ocean contains the ingredients needed to sustain life.

This new work which offers an additional scenario for some plumes proposes that they may come from pockets of water embedded in the frozen shell rather than from water pushed upward from the ocean below. The source of the plumes is important: water from the ice crust is considered less hospitable to life than the global internal ocean because it likely lacks the energy that is a necessary ingredient for life. In the ocean of Europe, that energy could come from hydrothermal vents on the sea floor.

“Understanding where these plumes of water come from is very important to know if future explorers of Europe could have the ability to actually detect life from space without probing the ocean of Europa,” said lead author Gregor Steinbrügge. , postdoctoral fellow at Stanford’s School of Earth, Energy & Environmental Sciences.

Using images collected by NASA’s Galileo spacecraft, the researchers developed a model to propose how a combination of freezing and pressurization could lead to a cryo-volcanic eruption or an explosion of freezing water. The results, published November 10 in Geophysical Research Letters, can shed light on eruptions on other icy bodies in the solar system.

The researchers focused their analyzes on Manannán, an 18-mile (29-kilometer) crater on Europa that resulted from an impact with another celestial object tens of millions of years ago. Reasoning that such a collision would generate tremendous heat, they modeled how the melted ice and subsequent freezing of the water pocket inside the frozen shell could pressurize it and cause the water to erupt.

“The comet or asteroid that hit the ice shell was basically a big experiment that we’re using to build hypotheses to test,” said co-author Don Blankenship, senior researcher at the University of Texas Institute for Geophysics (UTIG ) and principal investigator of the radar instrument, REASON (Radar for Europa Assessment and Sounding: Ocean to Near-surface), which will fly aboard NASA’s upcoming Europa Clipper spacecraft. “Our model makes specific predictions that we can test using radar data and other tools on the Europa Clipper.”

The model indicates that because Europa’s water partially froze following the impact, there may have been pockets of water remaining on the moon’s surface. These pockets of salt water can move laterally through Europa’s ice shell melting adjacent regions of ice and consequently become even saltier in the process.

A salty driving force

The model proposes that when a migrating brine pocket reached the center of the Manannán crater, it froze and began to freeze, generating pressure that ultimately resulted in a plume, estimated to be over a mile high (1, 6 kilometers). The eruption of this plume left a distinctive mark: a spider-like feature on the surface of Europa that was observed by Galileo’s images and incorporated into the researchers’ model.

“Although the plumes generated by the migration of the brine pockets would not provide a direct view of the ocean of Europa, our results suggest that the Europa ice shell itself is very dynamic,” said lead co-author Joana Voigt. graduate research assistant at the University of Arizona, in Tucson.

The relatively small size of the plume that would form at Manannán indicates that the impact craters likely cannot explain the source of other larger plumes on Europa that have been hypothesized based on data from Galileo and NASA’s Hubble Space Telescope, they said. researchers. But the process modeled for the Manannán eruption could take place on other icy bodies, even without an impact event.

“The work is exciting because it supports the growing body of research that shows there could be more types of plumes on Europa,” said Robert Pappalardo of NASA’s Jet Propulsion Laboratory in Southern California and project scientist on the Europa Clipper mission. “Understanding the plumes and their possible sources contributes greatly to Europa Clipper’s goal of investigating the habitability of Europa.”

Missions such as Europa Clipper help contribute to the field of astrobiology, interdisciplinary research into the variables and conditions of distant worlds that could host life as we know it. Although Europa Clipper is not a life-sensing mission, it will conduct a detailed reconnaissance of Europa and investigate whether the frozen moon, with its subterranean ocean, has the ability to support life. Understanding Europa’s habitability will help scientists better understand how life on Earth has developed and the potential to find life beyond our planet.