What’s That Spider-Shaped Thing on Jupiter’s Moon Europa?

On Europa, one of Jupiter’s icy moons, scientists have identified a feature that looks like a gigantic spider. It is not, of course. Instead, this giant spider-like asterisk-shaped scar is evidence that liquid water might be hiding beneath all of that ice.

The kilometer-wide spider blog thing was first spotted by NASA’s Galileo spacecraft decades ago. Now, a team of planetary scientists took another look at it and thinks there might be some water sloshing around under there.

The feature’s official name is Damhán Alla, a Gaelic term meaning “spider.” Well, if you want to be more ominous about it, it means explicitly “wall demon,” which is actually a terrific way to describe spiders.

The name comes from a research team led by physicist Lauren McKeown of the University of Central Florida, working with scientists from NASA’s Jet Propulsion Laboratory, Brown University, and Trinity College Dublin. Their findings were recently published in The Planetary Science Journal.

For quite some time now, researchers have figured it was likely that Europa had a vast saltwater sea beneath its cracked icy surface, making it one of the more promising spots in our solar system and in our search for life beyond Earth. Damhán Alla only reinforces that idea.

Scientists Are Investigating a Spider-Shaped Feature on Europa

McKeown’s team compared the European feature to “lake stars” on Earth. Those are small, branching patterns that form when water pushes up through ice on frozen lakes, melting snow in tree-like shapes. The physics that make that happen on Earth could be the very same at work on Europa… just scaled up and with much harsher conditions than anything we experience here at home.

As for why this specific one spread across the surface of Europa, researchers think an impact fractured the moon’s ice crust. That allowed pressurized saltwater to seep up through the cracks and spread, spiderlike, before it refroze.

The shape is all well and good and cool, but what’s more important is what the shape implies. If water can break through Europa’s ice in specific spots, that suggests the ocean below might be closer to the surface than previously thought.

It could also mean that pockets of salty seawater are trapped within the ice itself, kind of like how a partially frozen ice cube can be solid on the outside while some water still sloshes around inside.

So far, scientists have only unhelpful, low-resolution pics from Galileo to work with. That change will happen when NASA’s Europa Clipper mission arrives in the Jupiter system around 2030. It will be equipped with super-high resolution cameras that will reveal more of Jupiter and its moons than ever before.

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