Tectonism and Enhanced Cryovolcanic Potential Around a Loaded Sputnik
Planitia Basin, Pluto.
Abstract
Sputnik Planitia on Pluto is a vast plain consisting of a nitrogen ice
deposit filling a broad topographic depression, likely an impact basin.
The basin displays a broad, raised rim and is surrounded by numerous
extensional fracture systems, each with characteristic orientations with
respect to the basin center. The nitrogen ice exerts a large mechanical
load on the water ice outer shell crust (here also containing the
lithosphere). We calculate models of stress and deformation related to
this load, varying dimensional, mechanical, and boundary condition
properties of the load and Pluto’s lithosphere, in order to constrain
the conditions that led to the formation of the observed tectonic and
topographic signals. We demonstrate that the tectonic configuration is
diagnostic of a particular set of conditions that hold for the Sputnik
basin and Pluto, including moderate elastic lithosphere thickness (50 ±
10 km) and a wide load set into a basin that was pan-shaped and shallow
(~3 km) at the time of nitrogen deposition initiation.
These tectonic systems show the contributions of both flexural (bending)
and membrane (stretching) responses of the lithosphere, with the latter
dominating in proportion to the importance of spherical geometry effects
(i.e., wide loads). Rim topography may also show an influence of
primordial annular trans-basin ice shell thickening from the impact
process. Analysis of stress-driven cryomagma transport shows that
loading stresses can facilitate ascent of cryomagmas in annular zones
around the basin, the locations of which overlap the observed distances
from Sputnik of several candidate cryovolcanic sites.