Overview
- NASA reports that Juno’s Microwave Radiometer measured an average ~18-mile (29-km) thickness for Europa’s cold, conductive outer ice layer during a Sept. 29, 2022 flyby that passed within about 220 miles and sampled roughly half the moon.
- The peer-reviewed analysis, published Dec. 17, 2025 in Nature Astronomy, provides the first resolved subsurface constraints that distinguish between thin and thick ice-shell models for the region observed.
- The instrument detected small near-surface “scatterers” — cracks, pores, and voids a few inches across extending to hundreds of feet — which modeling indicates are unlikely to carry significant oxygen or nutrients down to the ocean.
- Study authors note key caveats: the estimate applies to the observed region and the outer conductive layer, a deeper convective layer would increase total thickness, and modest dissolved salts could reduce the estimate by about 3 miles.
- The results shape expectations for chemical exchange and habitability and will inform planning for Europa Clipper and JUICE, while Juno continues operations with its 81st Jupiter flyby scheduled for Feb. 25, 2026.