Impacts Churn the Surface of Europa

New research helps understand the effects of constant impact gardening on the surface of Jupiter’s moon Europa and how that may affect the search for life.

IMAGE: This image taken by NASA’s Galileo spacecraft in the late 1990s shows Europa’s ice shell, marked by fractures and impact craters, and it evokes a sense of mystery about what lies within it and beneath that shell. The color variations on the surface show that there’s communication between the surface and subsurface, the nature of which is a subject of intense study. This paper helps us to understand the effects of constant surface bombardment on materials that may be available for study at the surface. CREDIT: NASA/JPL-Caltech/SETI Institute

While Enceladus is on the radar for possible life, there are currently no missions planned to go to the tiny world. However, another icy moon, larger and just as interesting, Europa, is on the mission schedule with the Europa Clipper.

New research published in Nature Astronomy examines the results of “impact gardening” on the surface of Europa. For tens of millions of years, small impacts have churned the icy surface down to an average depth of 30 centimeters. That surface is scarred and battered, covered in tiny craters that fracture the ice. As with Enceladus, one of the issues with habitability is the radiation that hits the surface. Under the ice, life would be protected. But if that ice is being churned, some of the subsurface water could be brought to the surface, and evidence of life might be destroyed by the radiation. Some of that surface ice could also get moved into the water, mixing into the ocean and changing the chemical composition, possibly affecting any life.

Lead author Emily Costello notes: If we hope to find pristine, chemical biosignatures, we will have to look below the zone where impacts have been gardening. Chemical biosignatures in areas shallower than…