Detection of ammonia on Pluto's surface in a region of geologically recent tectonism

C M Dalle Ore; D P Cruikshank; S Protopapa; F Scipioni; W B McKinnon; J C Cook; W M Grundy; B Schmitt; S A Stern; J M Moore; A Verbiscer; A H Parker; K N Singer; O M Umurhan; H A Weaver; C B Olkin; L A Young; K Ennico

doi:10.1126/sciadv.aav5731

Detection of ammonia on Pluto's surface in a region of geologically recent tectonism

Sci Adv. 2019 May 29;5(5):eaav5731. doi: 10.1126/sciadv.aav5731. eCollection 2019 May.

Authors

C M Dalle Ore^{1

2}, D P Cruikshank², S Protopapa³, F Scipioni^{1

2}, W B McKinnon⁴, J C Cook⁵, W M Grundy⁶, B Schmitt⁷, S A Stern³, J M Moore², A Verbiscer⁸, A H Parker³, K N Singer³, O M Umurhan^{1

2}, H A Weaver⁹, C B Olkin³, L A Young³, K Ennico²

Affiliations

¹ SETI Institute, Mountain View CA, USA.
² NASA Ames Research Center, Moffett Field CA, USA.
³ Southwest Research Institute, Boulder CO, USA.
⁴ Department of Earth and Planetary Sciences and the McDonnell Center for the Space Sciences, Washington University, St. Louis, MO, USA.
⁵ Pinhead Institute, Telluride CO, USA.
⁶ Lowell Observatory, Flagstaff AZ, USA.
⁷ Université Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France.
⁸ Johns Hopkins University Applied Physics Laboratory, Laurel MD, USA.
⁹ University of Virginia, Charlottesville, VA, USA.

Abstract

We report the detection of ammonia (NH₃) on Pluto's surface in spectral images obtained with the New Horizons spacecraft that show absorption bands at 1.65 and 2.2 μm. The ammonia signature is spatially coincident with a region of past extensional tectonic activity (Virgil Fossae) where the presence of H₂O ice is prominent. Ammonia in liquid water profoundly depresses the freezing point of the mixture. Ammoniated ices are believed to be geologically short lived when irradiated with ultraviolet photons or charged particles. Thus, the presence of NH₃ on a planetary surface is indicative of a relatively recent deposition or possibly through exposure by some geological process. In the present case, the areal distribution is more suggestive of cryovolcanic emplacement, however, adding to the evidence for ongoing geological activity on Pluto and the possible presence of liquid water at depth today.

Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).

Publication types

Research Support, Non-U.S. Gov't