Jupiter’s moon Europa has a huge ocean beneath its icy surface and it used to be thought that sulfate salts dominate Europa’s oceans, but this may turn out not to be the case.

The Hubble Space Telescope has detected table salt on the surface of Europa according to a study. NASA’s Galileo spacecraft which orbited around Jupiter during the 1990s and the 2000s and spotted some unexpected yellow patches on the surface. Subsequent laboratory simulations showed that these patches may be indications of irradiated sodium chloride(Europa lies within Jupiter’s radiation belt). As a result, Trumbo et al. started a search for signs of sodium chloride in Europa using the Hubble Space Telescope Imaging Spectrograph(STIS).

Trumbo et al. observed a broad absorption line at 450 nanometers which corresponds to the absorption line of irradiated table salt, but this was only observed on the one hemisphere of the moon that always faces Jupiter. On top of this, these signs of irradiated sodium chloride were mainly concentrated in the active regions of Europa(which are located in the hemisphere facing Jupiter), the regions of Europa where materials from the ocean spew up to the surface. This hemisphere of Europa which constantly faces Jupiter is shielded from the sulfur compounds(which come from Jupiter’s moon Io) that rain down on Europa on its other hemisphere. Because of this, Trumbo et al. wrote in their study that the composition of elements in the active regions of Europa may be representative of what can be found in Europa’s subsurface ocean which implies that this sodium chloride may make up a big part of Europa’s oceans. It is unclear however whether this is true, however. While it is near certain that the sodium chloride is coming from Europa’s ocean underneath, it is uncertain that this sodium chloride does dominate the oceans of Europa. There is still a possibility of sulfate salts making up the majority of Europa’s oceans with sodium chloride being a minor part of it.

Nevertheless, this discovery is enough to reexamine the composition of Europa’s oceans and it brings new possibilities of the life that may inhabit Europa. This discovery also indicates that Europa is hydrothermally active. While there are still some uncertainties and questions to be answered about this discovery, the NASA Europa Clipper probe is expected to launch in the 2020s and should bring about a wealth of data to be examined by scientists and should give us a clearer picture of the composition of elements in Europa’s ocean.

The paper that made this discovery can be found here:

Click to access eaaw7123.full.pdf