James Webb Space Telescope spectral data shows that Jupiter’s moon Europa is undergoing constant surface changes, potentially allowing material from a subsurface ocean to reach the surface and strengthening the case for possible habitability.
The recent Southwest Research Institute (SwRI) experiments, led by Dr. Ujjwal Raut, attempted to verify potential dynamics across Europa’s icy surface, suggesting that some of Europa’s water ice could be more like that of Earth than previously thought.
Action on the Europan Surface
While ice covers Europa’s surface, it is not uniform, with some spots crystallizing at different rates than others. A range of complex interactions, both external and geological, may be at play in producing the uneven freeze.
While Europa’s water is a key ingredient in the hope for life, its surface water ice is different than that on Earth. Earth ice generally forms a crystalline structure as molecules order into a hexagonal pattern while freezing. On Europa, however, amorphous ice forms a top layer as charged particles bombard the surface, altering the crystalline structure.
Testing James Webb Space Telescope Findings
At SwRI, Dr. Raut works as a program manager in the Planetary Science Section. In a SwRI lab, his team conducted extensive experiments to illuminate what may be occurring with Europan ice. Their experiments identified the time scales required for ice amorphization and recrystallization on the Europan surface. Crucially, it paid significant attention to the tumultuous areas of the moon full of cracks, ridges, and plains, where divergent terrain features nestled up against one another.
Scientists have been suggesting for two decades that Europa does contain crystalline ice, with only the thin top layer distorted by charged particles into an amorphous form. This new work indicates that crystalline ice exists on the surface, instead of only buried beneath an amorphous veneer, most notably in the Tara Regio area.
“We think that the surface is fairly porous and warm enough in some areas to allow the ice to recrystallize rapidly,” said lead author Dr. Richard Cartwright, a spectroscopist at Johns Hopkins University’s Applied Physics Laboratory. “Also, in this same region, generally referred to as a chaos region, we see a lot of other unusual things, including the best evidence for sodium chloride, like table salt, probably originating from its interior ocean. We also see some of the strongest evidence for CO2 and hydrogen peroxide on Europa. The chemistry in this location is really strange and exciting.”
Europa’s Ocean
Dr. Raut says that his team’s results reinforce the likelihood that Europa does contain a subsurface liquid ocean.
“Our data showed strong indications that what we are seeing must be sourced from the interior, perhaps from a subsurface ocean nearly 20 miles beneath Europa’s thick icy shell,” Raut said. “This region of fractured surface materials could point to geologic processes pushing subsurface materials up from below. When we see evidence of CO2 at the surface, we think it must have come from an ocean below the surface. The evidence for a liquid ocean underneath Europa’s icy shell is mounting, which makes this so exciting as we continue to learn more.”
Tara Regio’s CO2 presents a mystery in itself. The area contains a common carbon isotope with an atomic mass of 12, composed of six protons and six neutrons, and a rarer isotope that has a heavier atomic mass of 13 due to having seven neutrons instead of six.
“Where is this 13CO2 coming from? It is hard to explain, but every road leads back to an internal origin, which is in line with other hypotheses about the origin of 12CO2 detected in Tara Regio,” Cartwright said.
The paper “JWST Reveals Spectral Tracers of Recent Surface Modification on Europa” appeared on May 28, 2025, in the Planetary Science Journal.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.