Europa, a moon of Jupiter, has long been one of the most exciting targets in the search for life beyond Earth. Many scientists believe that an ocean lies below its icy surface, potentially hosting geologic activity capable of supporting life, but what happens on the moon’s seafloor is still largely a mystery. Although discussions on Europa are mostly centered around this hidden ocean, the shell of ice that envelops the moon has its own surprises.
A study recently published in The Planetary Science Journal suggests that Europa’s surface ice is constantly changing. The evidence explored in the study paints a better picture of Europa’s outermost layer, and it may even reveal the interior processes that shape the moon’s unique structure.
Europa’s Surface Ice
Europa has the smoothest surface out of any known object in our Solar System, but it’s far from lacking variety. The surface is rife with distinct geologic features, such as ridges, plains, and cracks, that cross over each other. Their disorderly appearance is linked to a fitting name, “chaos terrain.”
Some regions with chaos terrain also provide insight on Europa’s surface ice. Most of Europa’s surface is made of amorphous ice, which lacks a crystalline structure. Scientists previously believed that Europa’s surface was entirely covered by a thin layer of amorphous ice, and that below this was crystalline ice (the form that most ice on Earth takes).
However, the researchers involved with the new study have confirmed that certain areas of Europa’s surface contain crystalline ice, aligning with spectral data captured by the James Webb Space Telescope (JWST). This same ice also appears below the surface in these regions as well.
“We think that the surface is fairly porous and warm enough in some areas to allow the ice to recrystallize rapidly,” said lead author Richard Cartwright, a spectroscopist at Johns Hopkins University, in a statement.
Read More: With Icy Volcanoes, the Moon Europa Is Obscure, Along With These 3 Other Moons
Activity in the Ocean
A few other factors have convinced the researchers that an ocean exists below Europa’s icy surface. The regions where ice recrystallizes show evidence of sodium chloride (what we know as table salt), carbon dioxide, and hydrogen peroxide.
“Our data showed strong indications that what we are seeing must be sourced from the interior, perhaps from a subsurface ocean nearly 20 miles (30 kilometers) beneath Europa’s thick icy shell,” said author Ujjwal Raut, a program manager at the Southwest Research Institute. “This region of fractured surface materials could point to geologic processes pushing subsurface materials up from below.”
The Europa Clipper’s Mission
Although Europa and its subsurface ocean will be a crucial target for future space exploration, some scientists have expressed doubts regarding its capacity to sustain life.
A series of obstacles could make finding life on Europa more difficult. At an American Geophysical Union conference last year, scientists reported that the ice layer covering the moon’s surface is thicker than expected, indicating that there may not be enough heat or activity in the subsurface ocean to support life. Scientists aren’t yet sure if an abundance of hydrothermal vents or seafloor volcanoes sit at the bottom of the ocean — these features have been crucial in driving life on our own planet.
Observations of Europa haven’t fully confirmed the existence of plumes, either, which would be a clear sign that material from the ocean could be transported to the surface.
About 5 years from now, in 2030, scientists will get an unprecedented view of Europa as NASA’s Europa Clipper approaches the icy moon. Launched last October, the Europa Clipper will reveal many secrets that still surround the moon’s surface and the ocean below. Among its various objectives, the mission will look for plumes, which would be able to eject microbes — if they truly do exist on the moon — into space for the Europa Clipper to examine.
Read More: NASA’s Europa Clipper Will Probe for Life in The Plumes of Icy Moons
Article Sources
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Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.
