The Pits of Pluto’s Sputnik Planitia: Volatile Loss Considerations

The NASA New Horizons spacecraft’s Long-Range Reconnaissance Imager (LORRI; Cheng et al. 2008) and Ralph multicolor camera/IR composition mapping spectrometer (Reuter et al. 2008) revealed that Pluto’s vast N₂/CH₄/CO-rich glacier called Sputnik Planitia (SP) exhibits many hundreds of multi-kilometer scale pits with apparently dark floors (e.g., Stern et al. 2015, 2018). Hoover et al. (2020) and Keeney et al. (2020) present studies of the statistical properties of pit sizes, locations, orientations, albedos, colors, and compositions in both LORRI and Ralph high spatial resolution strips obtained by New Horizons on Pluto. The estimated “missing mass” of N₂, CO, and CH₄, represented by the integrated pits volume on SP, is >100 times the mass of Pluto’s present-day atmosphere. We will explore the volatile loss implications of the pits for both Pluto’s atmosphere and its volatile transport.