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NASAJuno provided images that support the theory of Europa’s true polar wander, showing that the moon’s ice sheet has shifted. Images from the solar-powered spacecraft have revealed intriguing features of the ice-covered moon Jovian, including geological disturbances and potential plume activity, suggesting liquid water and brine reaching the surface.

Images captured by the JunoCam visible light camera aboard NASA’s Juno spacecraft support the theory that the ice crust at the north and south poles of JupiterEuropa’s moon isn’t where it was. Additionally, a high-resolution image from the spacecraft’s Stellar Reference Unit (SRU) shows indications of possible plume activity and disturbances in the ice shell, suggesting that brine may have recently come to the surface.

The JunoCam results were recently published in Planetary Science Journal and the SRU results were published in the journal JGR Planets.

On September 29, 2022, Juno made its closest flyby of Europa, coming within 220 miles (355 kilometers) of the moon’s frozen surface. The four images taken by JunoCam and one by SRU are the first high-resolution images of Europa since Galileo’s last flyby in 2000.

A real polar wander

Juno’s ground track over Europa allowed images near the moon’s equator. When analyzing the data, the JunoCam team found that along with the expected ice blocks, walls, cliffs, ridges and slopes, the camera also captured unevenly distributed steep-walled depressions 12 to 31 miles (20 to 50 kilometers) wide. They resemble large ovoid pits previously found in images from elsewhere in Europe.

A giant ocean is thought to lie beneath Europa’s icy exterior, and these surface features are linked to “true polar drift,” a theory that says Europa’s icy outer shell is essentially free-floating and moving.

This black-and-white image of Europa’s surface was taken by the Stellar Reference Unit (SRU) aboard NASA’s Juno spacecraft during the flyby on September 29, 2022. The Chaos feature, called the “Birdhead,” is visible at lower right angle. Credit: NASA/JPL-Caltech/SwRI

“True polar wander occurs if Europa’s ice shell separates from its rocky interior, leading to high levels of stress on the shell, leading to predictable fracture patterns,” said Juno co-investigator Candy Hansen, who led JunoCam planning. at the Planetary Science Institute in Tucson, Arizona. “This is the first time these fracture patterns have been mapped in the Southern Hemisphere, suggesting that the effect of true polar wander on Europa’s surface geology is more extensive than previously identified.”

High-resolution JunoCam imagery has also been used to reclassify a previously prominent surface feature from the Europa map.

“Gvern Crater is gone,” Hansen said. “What was once thought to be a 13-mile-wide impact crater – one of the few documented impact craters in Europe – Gwern was revealed in the JunoCam data as a set of intersecting ridges that create an oval shadow.”

This annotated image of Europa’s surface from Juno’s SRU shows the location of a double ridge running east-west (blue box) with possible fin patches and the chaos the team calls the “Bird’s Beak” (orange box). These features suggest ongoing surface activity and the presence of subsurface liquid water on the icy Jovian moon. Credit: NASA/JPL-Caltech/SwRI

The little bird

Although all five Juno images of Europa are high-resolution, the image from the spacecraft’s black-and-white SRU offers the most detail. Designed to detect faint stars for navigational purposes, the SRU is sensitive to low light. To avoid overexposing the image, the team used the camera to capture the night side of Europa while it was illuminated only by sunlight scattered by Jupiter (a phenomenon called the “Jupiter flare”).

This innovative approach to imaging allowed complex surface features to be highlighted, revealing complex networks of transverse ridges and dark patches of potential water vapor jets. One intriguing feature, which covers an area of ​​23 miles by 42 miles (37 kilometers by 67 kilometers), has been named by the team “The Birdcage” because of its shape.

Characterized by a chaotic terrain with hills, prominent ridges, and dark reddish-brown material, the platypus is the youngest feature in its neighborhood. Its northern “torso” and southern “beak” — connected by a fractured “neck” formation — interrupt the surrounding terrain with a lump of matrix material containing multiple ice blocks that are 0.6 to 4.3 miles (1 to 7 kilometers) wide. . The ridge formations collapse into the feature along the edges of the Ptitchechovka.

For the Juno team, these formations support the idea that Europa’s ice sheet may be retreating in places where there are pockets of salty water from the subsurface ocean below the surface.

About 31 miles (50 kilometers) north of Pticechovka is a set of twin ridges flanked by dark patches similar to features found elsewhere in Europe, which scientists have suggested are cryovolcanic jet deposits.

“These features suggest present-day surface activity and the presence of subsurface liquid water on Europa,” said Heidi Becker, lead co-investigator for the SRU at NASA’s Jet Propulsion Laboratory in Southern California, which also manages the mission. “The SRU image is a high-quality baseline for specific locations on NASA and ESA’s Europa Clipper mission (European Space Agency‘s) Sap missions can be directed to look for signs of alteration and brine.’

Europa Clipper’s focus is on Europa – including investigating whether the icy moon might have conditions suitable for life. It is scheduled to launch in the fall of 2024 and arrive at Jupiter in 2030. Juice (Jupiter Icy Moons Explorer) launched on April 14, 2023. The ESA mission will reach Jupiter in July 2031 to explore many targets (Jupiter’s three large icy moons, as well as fiery Io and smaller moons, along with the planet’s atmosphere, magnetosphere, and rings) with a special focus on Ganymede.

Juno made its 61st close flyby of Jupiter on May 12. Its 62nd flyby of the gas giant, scheduled for June 13, includes a flyby of Io at an altitude of about 18,200 miles (29,300 kilometers).

References:

“Juno’s JunoCam Images of Europa” by CJ Hansen, MA Ravine, PM Schenk, GC Collins, EJ Leonard, CB Phillips, MA Caplinger, F. Tosi, SJ Bolton and Björn Jonson, 21 March 2024, The Planetary Science Journal.
DOI: 10.3847/PSJ/ad24f4

Reference: “A complex region of Europa’s surface with hints of recent activity revealed by Juno’s Stellar Reference Module” by Heidi N. Becker, Jonathan I. Lunin, Paul M. Schenk, Megan M. Florence, Martin J. Brennan, Candace J. Hansen, Yasmina M. Martos, Scott J. Bolton and James W. Alexander, 22 Dec. 2023, Journal of Geophysical Research: Planets.
DOI: 10.1029/2023JE008105

JPL, a division of Caltech in Pasadena, Calif., manages the Juno mission for principal investigator Scott Bolton of the Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers program, which is managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington. The Italian Space Agency (ASI) funds Jovian’s InfraRed Auroral Mapper. Lockheed Martin Space in Denver built and operates the spacecraft.