Spiders on Jupiter? Scientists uncover secret origins of arachnid-like ‘demon’ lurking on gas giant’s moon.
A mysterious spider-like structure lurking on Jupiter’s fourth-largest moon, Europa, may finally have a proper explanation nearly 30 years after its discovery. The impostor arachnid has also been given a new demonic name.
In March 1998, NASA’s Galileo space probe — which studied Jupiter and its major moons between 1995 and 2003 — flew closely by Europa, a frozen ocean moon often considered one of the most likely places for extraterrestrial life exist in the solar system. During this flyby, the probe mapped an impact structure about 22 kilometers wide, nicknamed Manannán Crater, on the icy surface of the moon, and discovered something strange hiding there.
But in a new study, published December 2 in The Journal of Planetary Sciencethe researchers proposed an alternative explanation: that the Jovian spider formed in a way similar to how dark dendritic patterns on Earth, known as “lake stars,” typically form. These features form when snow falls on frozen lakes and water seeps through tiny holes in the ice.
With this in mind, researchers used a similar technique to partially recreate the mysterious shape of Manannán Crater in the laboratory. The study team also ultimately named the European arachnid asterisk Damhán Alla, meaning “spider” or “wall demon” in Irish. (Manannán is a Celtic god in Irish mythology, who partly inspired the new name.)
“Lake stars are really beautiful and they are quite common on frozen lakes and ponds covered in snow or slush,” lead author of the study. Laura McKeowna planetary scientist from the University of Central Florida, said in a statement. “It’s wonderful to think that they can give us insight into processes occurring on Europa and perhaps even on other icy ocean worlds in our solar system.”
However, rather than rising through tiny holes, as happens when lake stars form on Earth, Damhán Alla was likely born from an asteroid impact – which created a small crack in Europa’s icy shell that allowed salt water to seep upward and paint the spider-like pattern on the surface. (This asteroid impact likely occurred after the formation of Manannán Crater.)
Researchers have also noted similarities between Damhán Alla and the famous “Mars spiders,” which are dusty deposits on the surface of Mars that they look like swarming spiders seen from above. These false arachnids, known as araneiform terrain, form when ice immersed in carbon dioxide sublimatesor turns directly into gas. Mc Keown’s team has already recreated these features on Earth Also.
The shape similarities between Damhán Alla and spiders on Mars are due to the way “fluid flows through porous surfaces,” Mc Keown said. In theory, similar spider features could also form on other frozen ocean worlds, such as Enceladus, Saturn’s moonthat of Jupiter another moon Ganymede and the dwarf planet Cereswhich resides in the asteroid belt beyond Mars.
Mc Keown is currently setting up a new laboratory, which will focus on studying how these various spider-like features can form on different moons of the solar system. She hopes to be able to provide valuable information that could help inform NASA’s work. Europa Clipper Missionwhich was launched in October 2024 and will arrive at study Jupiter’s watery moon in depth in 2030.
“The significance of our research is really exciting,” Mc Keown said. “Surface features like these can tell us a lot about what’s going on beneath the ice. If we see more of them with Europa Clipper, they could indicate local brine pools beneath the surface,” she added.
And these pools could be a good place to start looking for signs of extraterrestrial life.
