A Complex Region of Europa’s Surface 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 (450-1100 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 3x104 km2 region between ~0-6°N and 43.5-51°W in remarkable detail. This innovative use of a high-resolution star camera, designed to detect dim stars, produced the highest resolution coverage of this region to date. Prior coverage by Galileo under high-sun conditions at 1 km resolution led to characterization of the terrain as ridged plains with undifferentiated linea. The SRU image reveals a much richer and 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 that has undergone a unique local geologic process. Low-albedo deposits, similar to features previously associated with hypothesized subsurface activity, flank nearby ridges. 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. 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. It reveals several relatively youthful features in a possibly dynamic region and presents new puzzles that await future high-resolution imagery.