(Photo: Wikimedia Commons/NASA/JPL-Caltech/SETI Institute)
NASA's Juno spacecraft captured new photos of its icy moon, Europa. The high-definition pictures captured by the JunoCam visible-light camera support the theory that the planet's north and south poles' icy crust was not where it used to be.
New High-Definition Photos of Jupiter's Moon Europa
The moon's icy surface was reached by Juno on its closest flyby of Europa on Sept. 29, 2022, at a distance of 220 miles (355 kilometers). Since Galileo's final flyby in 2000, there haven't been any high-resolution photos of Europa until the four taken by JunoCam and one by the SRU. Recently, the SRU and JunoCam results were published in JGR Planets and the Planetary Science Journal, respectively.
Juno's ground track over Europa made imaging close to the moon's equator possible. The JunoCam team discovered that, in addition to the ice blocks, walls, scarps, ridges, and troughs predicted, the camera also recorded irregularly dispersed, steeply-walled depressions ranging in width from 12 to 31 miles (20 to 50 kilometers).
They resemble sizable, ovoid pits seen in earlier images taken in different parts of Europa. These surface features have been linked to the notion of "true polar wander," which holds that Europa's outer ice shell is essentially free-floating and moves. A massive ocean lies beneath the continent's frozen cover.
According to Candy Hansen, a Juno co-investigator who oversees JunoCam planning at the Planetary Science Institute in Tucson, Arizona, true polar wander happens when Europa's icy shell separates from its rocky interior, creating high stress levels on the shell and predictable fracture patterns.
The fact that these fracture patterns have never before been charted in the southern hemisphere indicates that genuine polar wander has a broader impact on Europa's surface geology than previously thought.
Another application of the high-resolution JunoCam imagery is the reclassification of a once-prominent Europa map surface feature.
According to Hansen, Crater Gwern is gone. JunoCam data showed that Gwern, once believed to be a 13-mile-wide impact crater and one of Europa's few known impact craters, was an oval shadow formed by a series of crossing ridges.
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Europa's Youngest Feature -- The Platypus
One of the things that stood out in the five Europa images was the moon's complex surface features, which featured intricate networks of cross-cutting ridges and dark stains from possible water vapor plumes. The crew dubbed one remarkable feature, which spans 23 miles by 42 miles (37 kilometers by 67 kilometers), "the Platypus" due to its unique shape.
With its erratic topography, hummocks, noticeable ridges, and dark reddish-brown material, the Platypus is the newest landmark in the area. Its fractured "neck" formation connects its northern "torso" and southern "bill," which break up the surrounding terrain with a lumpy matrix material filled with numerous 0.6—to 4.3-mile (1—to 7-kilometer)- wide ice blocks. At the borders of the Platypus, ridge structures merge into the feature.
According to the Juno team, these structures lend credence to the theory that patches of briny water from the deep ocean may exist beneath Europa's surface, perhaps causing the ice shell to break.
A series of twin ridges, roughly 31 miles (50 km) north of the Platypus, are bordered by black stains that resemble structures elsewhere on Europa, which scientists have theorized to be cryovolcanic plume deposits.
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