On Earth, the sublimation of massive ice deposits at equatorial latitudes under cold and dry conditions in the absence of any liquid melt leads to the formation of spiked and bladed textures eroded into the surface of the ice. These sublimation-sculpted blades are known as penitentes. For this process to take place on another planet, the ice must be sufficiently volatile to sublimate under surface conditions and diffusive processes that act to smooth the topography must operate more slowly. Here we calculate sublimation rates of water ice across the surface of Jupiter’s moon Europa. We find that surface sublimation rates exceed those of erosion by space weathering processes in Europa’s equatorial belt (latitudes below 23°), and that conditions would favour penitente growth. We estimate that penitentes on Europa could reach 15 m in depth with a spacing of 7.5 m near the equator, on average, if they were to have developed across the interval permitted by Europa’s mean surface age. Although available images of Europa have insufficient resolution to detect surface roughness at the multi-metre scale, radar and thermal data are consistent with our interpretation. We suggest that penitentes could pose a hazard to a future lander on Europa.

在地球上，在没有任何液体融解的情况下，在寒冷和干燥的条件下，赤道纬度处大量冰沉积物的升华会导致形成尖刺状和叶片状的纹理侵蚀到冰的表面。这些升华雕刻的刀片被称为pen悔。为了使该过程在另一颗行星上发生，冰必须具有足够的挥发性，才能在地表条件下升华，并且使表面形貌平滑的扩散过程必须更慢地运行。在这里，我们计算出木星的月亮欧罗巴表面上水冰的升华率。我们发现，欧罗巴赤道带（纬度低于23°）的表面风化速率超过了空间风化过程所引起的侵蚀速率，而且这种条件将有利于pen悔性生长。我们估计，如果欧罗巴上的pen齿要在欧罗巴平均地表年龄所允许的范围内发育，那么它们平均可以到达赤道附近的深度为15 m，在赤道附近的距离为7.5 m。尽管可用的欧罗巴图像分辨率不足以检测多米尺度的表面粗糙度，但雷达和热数据与我们的解释一致。我们建议pen悔者可能对未来在欧罗巴的着陆器造成危害。