Scientists examine mysterious spider-like feature on Ice Moon Europa

Scientists have investigated a spider-like feature within the Manannan Crater on Europa, one of the ice moons in orbit around the Gas Giant. The feature was first discovered by NASA's Galileo spacecraft that was retired in 2003. The feature allows scientists a window into the ongoing subsurface processes on the ice moon. Europa is suspected to host a global subsurface saltwater ocean, and is one of the most promising places to find life elsewhere in the Solar System. The scientists used the lake stars on Earth as analogues, combined with field observations, lab experiments and modelling to understand the formation of the feature. 

The research has implications for future missions that might land on Europa, or any of the ice worlds without thick atmospheres. Such branching, tree-like features are known to form in the regolith near the south pole of Mars as well. On Mars, escaping gas from a seasonal dry ice layers erode dust and sand, resulting in the asterisk-shaped features. Scientists believe that the feature on Europa formed from an impact, when brine from beneath the ice shell extruded through the ice broken by the impact. This is similar to the process by which lake stars on Earth form, from snow falling on frozen lakes. 

Scientists have dubbed the feature Damhan Alla, which is Irish for 'spider' to distinguish it from the Martian spider formations. The researchers believe that the feature may have formed in a way similar to lake stars on Earth. An impact created the crater, and temporarily elevated the temperatures and pressures in the region, allowing a subsurface brine reservoir to erupt and spread through the porous surface ice. While Earth has a nitrogen rich atmosphere, the atmosphere of Europa is tenuous. The researchers recreated the environment of Europa in a lab. A paper describing the research has been published in The Planetary Science Journal.