Europa in true color, taken by Juno during that
September 2022 fly-by. Click for full image.
Using data produced by Juno during a 2022 close-fly of Jupiter’s moon Europa, scientists have made a new estimate of the thickness of Europa’s icy crust, approximately 18 miles thick with a 6-mile margin of error.
In other words, their estimate could be as small as 12 miles thick, or as large as 24 miles thick.
You can read their paper here. From their abstract:
For the idealized case of pure water ice, the data are consistent with the existence of a thermally conductive ice shell with a thickness of 29 ± 10 km [18 ± 6 miles] and with the presence of cracks, pores or other scatterers extending to depths of hundreds of metres below the surface with a characteristic size smaller than a few centimetres in radius. An ice-shell salinity of 15 mg kg−1, as indicated by models based on terrestrial marine ice, would reduce our estimate of the thickness of the ice shell by about 5 km, substantially less than our 10 km uncertainty. The low volume fraction, small size and shallow depth of the scatterers indicate that the fracture interfaces observed at Europa’s surface are alone unlikely to be capable of carrying nutrients between the surface and the ocean. [emphasi mine]
The highlighted sentence is the important one. If this new estimate is right, than the unidentified reddish material that appears to leak out of the long ridgelike cracks on Europa’s surface, clearly visible in the picture to the right, are not coming from any underground ocean. The distances are too large.
Other estimates have suggested that ice crust could be as thin as 2 miles, but like this research the uncertainties are very large.
Meanwhile, the Juno mission is still alive, though essentially winding down operations. The mission was expected to officially end at the end of September 2025, when its budget ran out, but the just passed budget included enough money to keep it going, albeit at a relatively low level. According to the orbiter’s webpage, it will continue to orbit Jupiter, its orbit degrading naturally until it falls into Jupiter to burn up. As it does so data will continue to be collected, though at a much lower rate.
