NEWS FROM EUROPA

Table salt on the surface

Europa has had visitors, notably NASA’s Voyager and Galileo. On their flybys of the moon, analyses showed that the icy crust consisted of water ice and a substance originally thought to be magnesium sulphate. After revisiting the surface using the W. M. Keck Observatory based in Hawaii and Hubble, astronomers now know that it wasn’t magnesium sulphate and is actually sodium chloride – more commonly known as table salt. It was laboratory tests by Kevin Hand at NASA’s Jet Propulsion Laboratory that revealed that irradiated ocean salts under Europa-like conditions exhibit distinct features and a yellowish colour – table salt exhibits this colour on the surface of Europa, confirming its presence.

Setbacks for the next explorer

Unfortunately, the Europa Clipper mission, an orbiter that will spend about three years at the moon, and the proposed Europa Lander mission have come under scrutiny after a nine-month investigation concluded that there are serious issues that need to be addressed in order to satisfy both NASA and US Congress. After finding these conflicts of interest and issues in the budget, the investigation team concluded that ten changes must be made to get the project back on track, including altering the overall staffing regime, rescheduling milestones and making sure that any estimates be made in accordance with other projects. With these changes, it’s hoped the 2024 launch of Europa Clipper can go ahead.

Struggling to find plumes

Europa shares similarities with Saturn’s moon Enceladus: both exhibit signs of a subsurface ocean that could potentially harbour life.

One major difference, however, is that Enceladus has been studied much more thoroughly, courtesy of NASA’s Cassini. In its close-up analysis, Cassini detected plumes of material emerging from the surface of Enceladus, along with a distinct temperature spike in the data to match. However, this doesn’t appear to be the same for Europa, suggesting that either Europa plumes are very different, the plumes are only occasional, that they don’t exist or that their thermal signature is too small to have been detected by current data.