Tectonism and enhanced cryovolcanic potential around a loaded Sputnik Planitia basin, Pluto

Abstract

The bright Sputnik Planitia region on Pluto is a vast plain consisting of a deposit of frozen nitrogen that fills a broad depressed area. The depression is probably the result of a large object colliding with Pluto; such a depression is called an impact basin. The basin displays a broad, raised rim and is surrounded by numerous cracks that reach outward like spokes on a bicycle wheel. The frozen nitrogen pushes down the outer shell of Pluto, which consists of frozen water (ice). The pushing creates stress in the shell that can fracture it. We use computer models to test for the conditions that would create the configuration of cracks seen around Sputnik Planitia. We show that the models strongly favor a particular range for the shell thickness, 40–75 km. Also, for the most successful models the starting shape of the depression resembled that of a frying pan, and was around 3 km in depth. The stresses created in the ice shell actually assist the rising of liquid water through it, an unusual form of volcanism that may be occurring at several sites in the region surrounding Sputnik Planitia.