I always find it amusing and interesting how, in the lead-up to a planetary mission launch, scientists start using every possible space and ground telescope to stare at the future target ahead of arrival. We saw this with New Horizons where the Hubble Space Telescope helped discover two more moons at Pluto as the team was looking for potential spacecraft hazards. And now, as we get closer to the planned launch date for Europa Clipper in 2024, Hubble is at it again.

Using ultraviolet observations taken by Hubble, a team of scientists has mapped out the sulfur residue on the surface of Europa. Okay, that sounds like a somewhat weird thing to map out on a planet with an icy surface and a potentially massive subsurface ocean, but bear with me here. All of that sulfur on the surface could help us understand the composition of the ocean, and in that ocean rests some of our hopes for finding life beyond Earth.

Not unexpectedly, the new ultraviolet map for sulfur dioxide correlates with images taken in visible wavelengths that show dark surface regions. What’s even more interesting is that the sulfur is mostly concentrated on Europa’s trailing side. Co-author Philippa Molyneux explains: Most of the sulfur dioxide is seen on the ‘trailing’ hemisphere of Europa. It’s likely concentrated there because Jupiter’s co-rotating magnetic field traps sulfur particles spewing from Io’s volcanoes and slams them against the backside of Europa.

That magnetic field then causes a chemical reaction between the water that reaches the surface on Europa and the sulfur that arrives from Io, creating the sulfur dioxide residue.

On a side note, this paper also confirmed that the suspected water ice on Europa does not look like water ice in the ultraviolet. The team will continue to investigate this discrepancy, but an answer may have to wait until Europa Clipper reaches the Jovian system and sends back data.

More Information

SwRI press release

“Mid-ultraviolet Hubble Observations of Europa and the Global Surface Distribution of SO2,” Tracy M. Becker et al., 2022 June 2, The Planetary Science Journal