What geological features on Earth can be used to better understand unique geological features on Jupiter’s icy moon, Europa? This is what a recent study published in *The Planetary Science Journal* hopes to address as a team of researchers investigated potential Earth analogs for studying a unique geological feature on Europa scientists identified almost 30 years ago. This study has the potential help scientists gain insights into Europa’s unique geological features, some of which scientists hypothesize are caused by the moon’s internal liquid water ocean.
For the study, the researchers conducted a series of field tests at sites in Breckenridge, CO from November 19-25, 2022, known as Ollie’s Pond and Maggie Pond. The goal was to examine geological features known as “lake stars” that mirror features within Europa’s Manannán crater known as a “spider”, with the feature officially being called Damhán Alla. To accomplish this, the team used a common radar method called lidar to obtain in-depth measurements of each spider.
For Maggie Pond, the researchers identified five spiders while they observed many more spiders at Ollie’s Pond, along with observing spiders in several layers of ice. Laboratory experiments were then conducted to ascertain whether spiders could form under Europa-like conditions, including producing Europa surface ice simulant based on grain size and flow experiments involving a temperature-controlled box and freezing water.
In the end, the researchers concluded that the spider features on Europa likely form within a slushy material beneath the hard and icy surface crust. The researchers note how these spiders complement long-known surface features on Europa caused by liquid water. Finally, the researchers note how their modeling revealed how these features could indicate past near-surface liquid water reservoirs on Europa. They are quick to note how further questions remain, including the uniqueness of these features to Manannán crater based on current images.
The study concludes, “If the recently launched Europa Clipper mission reveals similar morphologies, our understanding of lake stars in the context of Europan conditions may elucidate subsurface conditions and how the subsurface might be habitable. Europa Clipper will provide high-resolution and hyperspectral images as well as data on surface topography and thermal state. These future observations might enable the detection of other spider-like features at Europa and provide understanding on their formation mechanism, informing on surface and subsurface post-impact conditions and their implications for ice shell habitability.”
Due to the interactions between its subsurface ocean and icy surface, Europa has some of the most unique surface features in the entire solar system. For example, unlike the rest of the rocky objects scattered throughout the solar system, including planets, moons, asteroids, and comets, Europa is almost entirely devoid of impact craters. Instead, its surface displays unique structures like the spider features analyzed in this study, hypothesized to form from a slushy material due to the surface-ocean interactions.
Examples of other unique surface features on Europa caused by the surface-ocean interactions include chaos terrain, which displays broken and jumbled chunks of ice that have been drifted out of place and reassembled over time, with hypotheses regarding their formation mechanisms including ice shell melting or pockets of liquid water right beneath the surface ice.
As noted, NASA’s Europa Clipper is currently cruising to Europa with an estimated arrival date of April 2030. Once there, Clipper will perform approximately 50 close flybys of the small moon as it performs highly elliptical orbits, so it doesn’t stay within Jupiter’s massive and powerful magnetic field for too long. This is because the radiation from the magnetic field could damage the electronics and other essential aspects of the spacecraft, rendering it useless to conduct key science. One of the primary mission objectives will be to ascertain if Europa actually has a subsurface ocean, how it interacts with the surface, the habitability potential, and gaining data for future missions.
Another goal will be to image Europa’s surface, as only approximately 10 to 14 percent of the surface has been mapped with desirable image resolutions, with Clipper estimated to mapped approximately 95 percent of the surface. These new images could help gain insight into unique surface features like the spiders discussed in this study, along with other features that might have yet to be discovered.
What new insight into Manannán crater and Europa’s unique surface features will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
