NASA and ESA announce that spectrographic analysis of Hubble Space Telescope data gathered during observations of Jupiter’s icy moon Europa reveals that Europa has a persistent atmosphere of water vapor, but only on the hemisphere of the moon that is opposite of the direction of its orbital motion. (This unusual effect had been predicted in computer modeling, but had not been directly observed until now.) The atmosphere is present in Hubble spectroscopy data as old as 1999 and as recent as 2015. The stability of the water vapor in the atmosphere is the real surprise find, since surface-based water was assumed to be in solid ice form.
