The surface of Jupiter’s moon Europa features a widely varied landscape, including ridges, bands, small rounded domes and disrupted spaces that geologists call “chaos terrain.” Three newly reprocessed images, taken by NASA’s Galileo spacecraft in the late 1990s, reveal details in diverse surface features on Europa that Arthur C. Clarke, author of Space Odyssey 2001, famously warned future spacemen to “attempt no landing”.
Some 15 miles below the chaotic terrain of the surface lies the rocky bottom of Europa’s ocean, which is almost like a miniature Earth, with plate tectonics, continents, deep trenches, and active spreading centers, says Caltech’s Mike Brown. “Think about mid-ocean ridges on Earth,” he says, “with their black smokers belching scalding nutrient-rich waters into a sea floor teaming with life that is surviving on these chemicals. It doesn’t take much of an imagination to picture the same sort of rich chemical soup in Europa’s ocean leading to the evolution of some sort of life, living off of the internal energy generated inside of Europa’s core. If you’re looking for Europa’s whales – which many of my friends and I often joke that we are – this is the world you want to look for them on.”
Although the data captured by Galileo is more than two decades old, scientists are using modern image processing techniques to create new views of the moon’s surface in preparation for the arrival of the Europa Clipper spacecraft. The orbiter of Jupiter will conduct dozens of flybys of Europa to learn more about the ocean beneath the moon’s thick icy crust and how it interacts with the surface. The mission, set to launch in the next several years, will be the first return to Europa since Galileo.
“We’ve only seen a very small part of Europa’s surface at this resolution. Europa Clipper will increase that immensely,” said planetary geologist Cynthia Phillips of NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena. As a Europa project staff scientist, she oversees a long-term research project to reanalyze images of the moon.
The above map shows locations where each image, showcasing a variety of features, was captured by Galileo during its eighth targeted flyby of Jupiter’s moon Europa.
All three images were captured along the same longitude of Europa as Galileo flew by on Sept. 26, 1998, in the eighth of the spacecraft’s 11 targeted flybys of Europa. High-resolution images revealing features as small as 500 yards (460 meters) across were taken through a clear filter in grayscale (black and white). Using lower-resolution color images of the same region from a different flyby, technicians mapped color onto the higher-resolution images – a painstaking process.
Enhanced-color images like these allow scientists to highlight geologic features with different colors. Such images don’t show Europa as it would appear to the human eye, but instead exaggerate color variations to highlight different chemical compositions of the surface. Areas that appear light blue or white are made of relatively pure water ice, and reddish areas have more non-ice materials, such as salts.
Planetary scientists study high-resolution images of Europa for clues about how the surface formed. At an average of 40 million to 90 million years old, the surface we see today is much younger than Europa itself, which formed along with the solar system 4.6 billion years ago. In fact, Europa has among the youngest surfaces in the solar system, one of its many intriguing oddities.
The long, linear ridges and bands that crisscross Europa’s surface are thought to be related to the response of Europa’s icy surface crust as it is stretched and pulled by Jupiter’s strong gravity. Ridges may form when a crack in the surface opens and closes repeatedly, building up a feature that’s typically a few hundred yards tall, a few miles wide and can span horizontally for thousands of miles.
In contrast, bands are locations where cracks appear to have continued pulling apart horizontally, producing wide, relatively flat features.
The Daily Galaxy, Sam Cabot, via JPL