Europa’s Icy Crust Is ‘Free-Floating’ Across the Moon’s Hidden Ocean, New Juno Images Suggest

Europa’s icy shell shifts over an ocean holding twice Earth’s water volume.

Key Takeaways

  1. NASA’s Juno spacecraft confirms Europa’s icy crust is likely free-floating over a hidden ocean.
  2. The moon’s icy shell appears to have shifted from its original location, revealing surface activity.
  3. High-resolution images from Juno’s SRU revealed intricate ridges, fractures, and cryovolcanic evidence.
  4. A newly identified feature, “Platypus,” supports the theory of subsurface briny water pockets.
  5. Upcoming missions like Europa Clipper and JUICE will probe further into Europa’s potential for life.

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On September 29, 2022, NASA’s Juno spacecraft made its closest approach to Europa, coming within 220 miles (355 kilometers) of the Jovian moon’s icy surface. This historic flyby revealed remarkable details about Europa’s chaotic terrain, suggesting that its outer ice shell is free-floating over a hidden ocean. The findings, published in the Planetary Science Journal and JGR Planets, provide compelling evidence of active geological processes and the presence of subsurface liquid water.

Europa’s surface features intricate networks of ridges and dark stains, indicating possible water plumes venting from below the ice. High-resolution images from Juno’s Stellar Reference Unit (SRU) captured double ridges and grooves, along with small white dots caused by high-energy particles from the moon’s radiation-heavy environment. The images also revealed a unique feature called “Platypus,” a 42-mile-wide (67-kilometer-wide) structure with ridges and reddish-brown material, believed to be influenced by pockets of briny water beneath the surface.

Image: NASA/JPL-Caltech/SwRI
Image: NASA/JPL-Caltech/SwRI

True Polar Wander and Evidence of Subsurface Water

One of the most significant discoveries is the confirmation of “true polar wander,” a phenomenon where Europa’s icy shell shifts due to decoupling from its rocky interior. This movement creates high stress on the crust, resulting in predictable fracture patterns that were mapped for the first time in the moon’s southern hemisphere. These patterns suggest extensive geological activity and provide further support for the presence of an ocean beneath Europa’s icy crust.

Additional analysis prompted a reevaluation of previously identified features. For example, a 13-mile-wide (21-kilometer-wide) feature called Gwern, initially thought to be an impact crater, was determined to be intersecting ridges forming an oval shadow.

Image: Image data: NASA/JPL-Caltech/SwRI/MSSS. Image processing: Björn Jónsson (CC BY 3.0)
Image: Image data: NASA/JPL-Caltech/SwRI/MSSS. Image processing: Björn Jónsson (CC BY 3.0)

Europa’s hidden ocean, thought to contain twice as much water as all of Earth’s oceans combined, makes it a prime candidate for studying extraterrestrial life. NASA’s Europa Clipper mission, set to arrive at Jupiter in 2030, will investigate Europa’s magnetic field and search for definitive evidence of its ocean. Similarly, the European Space Agency’s JUICE mission aims to explore Europa and other Jovian moons with subsurface oceans.

These groundbreaking findings not only deepen our understanding of Europa’s dynamic geology but also set the stage for future exploration of its habitability and potential for hosting life.

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