A Complex Region of Europa's Surface With Hints of Recent Activity Revealed by Juno's Stellar Reference Unit

On 29 September 2022 Juno's low-light sensitive Stellar Reference Unit (SRU) captured a high-resolution (256-340 m/pixel) broadband (450-1,100 nm) visible image of Europa's icy surface during the first close flyby of the Jovian moon since Galileo's last encounter in 2000. Collected at a sub-spacecraft altitude of 412 km while the surface was illuminated only by Jupiter-shine (incidence angle: 48-51°), the SRU image reveals a 3 × 10⁴ km² region between ∼0°-6°N and 43.5°-51°W in remarkable detail at the highest resolution to date. Prior coverage by Galileo under high-sun conditions at 1 km resolution led to the characterization of the terrain as ridged plains with undifferentiated linea. The SRU image reveals a much richer and more complex picture. Intricate networks of cross-cutting ridges and lineated bands surround an intriguing 37 km (east-west) by 67 km (north-south) chaos feature with a concentric fracture system, depressed matrix margins, and low-albedo materials potentially associated with brine infiltration. The morphology and local relief of the chaos feature are consistent with formation in the collapse of ice overlying a salt-rich lens of subsurface water. Low-albedo deposits, similar to features previously associated with hypothesized cryovolcanic plume activity, flank nearby ridges. The SRU's high-resolution view of many types of features in a single image allows us to explore their regional context and greatly improve the geologic mapping of this part of Europa's surface. The image reveals several relatively youthful features in a potentially dynamic region, providing baselines for candidate locations that future missions can investigate for present day surface activity.