Giant Ice Spikes on Europa Could Endanger Future Landers

Jupiter’s moon Europa has captured the attention of scientists with its likely subsurface ocean and cracked icy shell, but visiting the distant iceball might be even harder than we thought. A new analysis of the conditions on Europa says we could encounter pointy spears of ice on the surface up to 50 feet tall, which may skewer any lander unlucky enough to come down in the wrong place. We don’t know how dangerous a landing would be yet, but the answers could present themselves in the next few years.

Europa is one of the most famous moons in the solar system, even though it’s relatively unexplored. The most recent mission to capture close-up images was Galileo more than 20 years ago. That mission helped scientists confirm there was a liquid body under the surface of Europa, but the nature of the ocean is unclear. To know for certain, you’d have to land on the surface and conduct experiments. However, Daniel Hobley of Cardiff University and his team say Europa won’t make that easy. The same remodeling of the surface that helped confirm the presence of water may also make the surface vastly more dangerous.

According to the new study, Europa likely forms ice structures called penitentes seen in Antarctica here on Earth. It begins with ice and snow building up unevenly on a surface. Sublimation causes some ice to change phases from solid directly to gas, but it doesn’t happen uniformly. Denser areas sublimate more slowly, eventually forming large spikes. On Earth, these spires can be taller than a person. On Europa with its lower gravity, they could be 50 feet tall.

The good news is Europa’s ongoing surface remodeling means not all areas will have giant penitentes blocking access. There should be flatter regions where a probe can set down safely. The bad news is those areas may be harder to reach in the first place. Hobley predicts the penitentes will be largest around the equator. That’s also the easiest place for a probe to land because it takes a lot of fuel to change orbital inclination. Scientists may need to build future landers with that in mind.

We’ll have a better idea what the surface of Europa is like in a few years. NASA has plans to launch the Europa Clipper mission in the early 2020s to survey the planet. The ESA also has a Ganymede probe that will make a few passes over Europa around the same time.

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