Scientists Think Europa’s Equator Might Be Covered in 45-Foot-Tall Ice Spears

Sharp spikes called penitentes may be waiting to impale any spacecraft that lands in the moon's low latitudes.
Penitentes in Argentina. Image: Arvaki

Europa, an ice moon orbiting Jupiter, is one of the most promising places to search for extraterrestrial life in the solar system. Slightly smaller than Earth’s Moon, Europa is thought to contain a vast subsurface ocean that may be habitable, or is perhaps already inhabited.

So what’s the hold-up? Why haven’t we landed on Europa to look for aliens? Exploring this tantalizing moon is a lot easier said than done, as demonstrated by a paper published Monday in Nature Geoscience. Led by Daniel Hobley, a geoscientist at Cardiff University, the research outlined the latest challenge for Europa lander missions—the risk of being impaled by 45-foot-tall snow spikes called penitentes.


Penitentes are sculpted from snowfields by unequal distributions of sunlight, which create a positive feedback loop of sublimation—solids transitioning to gas—that forms the unique towers. Named for their resemblance to the religious rites of penance in Catholicism, these structures have been observed on Earth and Pluto.

Europa has not been imaged closely enough to confirm if penitentes exist at its surface, but Hobley and his colleagues calculate that the moon possesses ideal conditions to grow the ice blades, especially at its equator. Radar observations of Europa also show scattered feedback around its equatorial regions, which could be caused by vast fields of penitentes that do not reflect light as powerfully as smoother regions of the moon.

"The presence of sharp, blade-like structures towering to almost 15 metres high would make any potential landing mission to Europa extremely precarious,” Hodley said in a statement. “We hope that studies like ours will help the engineers to develop innovative ways of delivering landers safely on Europa's surface so that we can find out even more about this fascinating place, and potentially look for signs of extraterrestrial life."

Read More: Signs of Alien Life on Europa Might Only Be Centimeters Under the Surface

Intimidating snow spears are not the only obstacles to finding life at Europa’s equator. In July, an unrelated study found that the moon’s lower latitudes are regularly dosed with damaging blasts of radiation from Jupiter’s magnetosphere. These “radiation lenses” are dangerous both for spacecraft and any life-forms that might exist on or near the surface.

Given these new findings, perhaps Europa missions should focus on high-latitude polar regions, where landers would be less likely to be damaged by ice spikes or wiped out by radiation punches.

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