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 degrees), the SRU image reveals a 3 x 104 km2 region between similar to 0 degrees-6 degrees N and 43.5 degrees-51 degrees 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. On 29 September 2022, the Juno spacecraft performed the first close flyby of Jupiter's icy moon Europa in generation. The low-light sensitive Juno SRU navigation camera was used to photograph a part of the surface that was lit only by sunlight scattered off Jupiter, from a spacecraft-to-surface distance of 412 km. This innovative use of a high-resolution star camera designed to detect dim stars produced Juno's highest resolution image of Europa, and provides the highest resolution coverage of the targeted region to date. The imaged area is revealed to be incredibly complex and rich with many different types of terrains and features. Dark stains that may be associated with plumes, and an area of ice shell disruption nicknamed "the Platypus," are compelling targets for future missions to investigate possible present day surface activity. Juno's Stellar Reference Unit imaged Europa's surface at high resolution while it was illuminated by Jupiter-shineThe image reveals a feature-rich region between 0 degrees-6 degrees N and 43.5 degrees-51 degrees W with hints of relatively recent activityA young 37 km by 67 km chaos feature and some low-albedo deposits adjacent to double ridges may be associated with subsurface liquid water