Hubble Explores Surface of Europa in Mid-UV

by johnsmith

The new mid-ultraviolet (UV) maps of Europa, created using data from the Space Telescope Imaging Spectrograph (STIS) instrument aboard the NASA/ESA Hubble Space Telescope, show concentrations of sulfur dioxide on the trailing side of the icy moon.

Map of sulfur dioxide (a) band depth and (b) band area for all four Hubble visits. Image credit: NASA / JPL / Bjorn Jonsson / Becker et al., doi: 10.3847/PSJ/ac69eb.

Map of sulfur dioxide (a) band depth and (b) band area for all four Hubble visits. Image credit: NASA / JPL / Bjorn Jonsson / Becker et al., doi: 10.3847/PSJ/ac69eb.

Discovered by Galileo Galilei and Simon Marius in 1610, Europa is the sixth of Jupiter’s moons and the fourth largest.

The moon is characterized by its bright, icy shell that is primarily composed of water ice harboring a liquid water ocean below.

It is the primary target of NASA’s upcoming Europa Clipper mission and will be explored through several close encounters during ESA’s upcoming JUICE mission.

“Europa’s relatively young surface is primarily composed of water ice, although other materials have been detected across its surface,” said Dr. Tracy Becker, a researcher at the Southwest Research Institute and the University of Texas at San Antonio.

“Determining whether these other materials are native to Europa is important for understanding the icy moon’s formation and subsequent evolution.”

“Assessing the surface material can provide insights into the composition of the subsurface ocean.”

Using Hubble’s STIS instrument, Dr. Becker and colleagues observed Europa at wavelengths between 180 and 320 nm.

“Our dataset is the first to produce a near-global map of sulfur dioxide that correlates with large-scale darker regions in both the visible and the ultraviolet wavelengths,” said Dr. Philippa Molyneux, a researcher at the Southwest Research Institute.

“The results were not surprising, but we did get much better coverage and resolution than previous observations.”

“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.”

Io is another of Jupiter’s largest moons but, in contrast, is considered the most volcanic body in the Solar System. Jupiter’s magnetic field can cause chemical reactions between the water ice and the sulfur, creating sulfur dioxide on Europa’s surface.

“In addition to studying the sulfur dioxide on the surface, we are continuing to try to understand the puzzle of why Europa — which has a surface that is known to be dominated by water ice — does not look like water ice at ultraviolet wavelengths, as confirmed by this study,” Dr. Becker said.

“We are actively working to understand why.”

The results appear in the Planetary Science Journal.


Tracy M. Becker et al. 2022. Mid-ultraviolet Hubble Observations of Europa and the Global Surface Distribution of SO2. Planet. Sci. J 3, 129; doi: 10.3847/PSJ/ac69eb

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