The findings were published in the Planetary Science Journal and JGR Planets.
On September 29, 2022, Juno flew within 220 miles of Europa's surface, capturing the first high-resolution images since Galileo's flyby in 2000.
Juno's ground track over Europa allowed for imaging near the equator. The JunoCam team identified irregularly distributed steep-walled depressions. These depressions are 12 to 31 miles wide and resemble large pits previously found.
A giant ocean is thought to exist beneath Europa's icy surface, with these features associated with "true polar wander," a theory suggesting Europa's ice shell moves independently of its rocky interior.
"True polar wander occurs if Europa's icy shell is decoupled from its rocky interior, resulting in high stress levels on the shell, which lead to predictable fracture patterns," said Candy Hansen, a Juno co-investigator. "This is the first time that these fracture patterns have been mapped in the southern hemisphere, suggesting that true polar wander's effect on Europa's surface geology is more extensive than previously identified."
The high-resolution imagery has also reclassified a prominent surface feature.
"Crater Gwern is no more," Hansen said. "What was once thought to be a 13-mile-wide impact crater - one of Europa's few documented impact craters - Gwern was revealed in JunoCam data to be a set of intersecting ridges that created an oval shadow."
The image from Juno's Stellar Reference Unit (SRU) offers the most detail. The SRU, sensitive to low light, captured Europa's nightside lit by Jupiter-shine, revealing intricate surface features and potential plume deposits.
One feature, covering 23 by 42 miles, was nicknamed "the Platypus" due to its shape. It is characterized by chaotic terrain with ice blocks and prominent ridges, suggesting Europa's ice shell may give way where subsurface briny water is present.
About 31 miles north of the Platypus, double ridges flanked by dark stains suggest possible cryovolcanic plume deposits.
"These features hint at present-day surface activity and the presence of subsurface liquid water on Europa," said Heidi Becker, lead co-investigator for the SRU. "The SRU's image is a high-quality baseline for specific places NASA's Europa Clipper mission and ESA's (European Space Agency's) Juice missions can target to search for signs of change and brine."
Europa Clipper aims to investigate Europa's potential for life, scheduled to launch in fall 2024 and arrive at Jupiter in 2030. Juice, launched in April 2023, will reach Jupiter in July 2031 to study the icy moons and the planet's atmosphere.
Juno executed its 61st close flyby of Jupiter on May 12. Its 62nd flyby, scheduled for June 13, includes an Io flyby at an altitude of about 18,200 miles.
Research Report:Juno's JunoCam Images of Europa
Related Links
Juno at NASA
The million outer planets of a star called Sol
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