Are NH$_3$ and CO$_2$ ice present on Miranda?

Riley A. DeColibus; Nancy J. Chanover; Richard J. Cartwright

doi:10.3847/PSJ/acf834

paper

Are NH $_{3}$ and CO $_{2}$ ice present on Miranda?

arXiv:2309.04844 · doi:10.3847/PSJ/acf834

Abstract

Published near-infrared spectra of the four largest classical Uranian satellites display the presence of discrete deposits of CO $_{2}$ ice, along with subtle absorption features around 2.2 $μ$ m. The two innermost satellites, Miranda and Ariel, also possess surfaces heavily modified by past endogenic activity. Previous observations of the smallest satellite, Miranda, have not detected the presence of CO $_{2}$ ice, and a report of an absorption feature at 2.2 $μ$ m has not been confirmed. An absorption feature at 2.2 $μ$ m could result from exposed or emplaced NH $_{3}$ - or NH $_{4}$ -bearing species, which have a limited lifetime on Miranda's surface, and therefore may imply that Miranda's internal activity was relatively recent. In this work, we analyzed near-infrared spectra of Miranda to determine whether CO $_{2}$ ice and the 2.2- $μ$ m feature are present. We measured the band area and depth of the CO $_{2}$ ice triplet (1.966, 2.012, and 2.070 $μ$ m), a weak 2.13- $μ$ m band attributed to CO $_{2}$ ice mixed with H $_{2}$ O ice, and the 2.2- $μ$ m band. We confirmed a prior detection of a 2.2- $μ$ m band on Miranda, but we found no evidence for CO $_{2}$ ice, either as discrete deposits or mixed with H $_{2}$ O ice. We compared a high signal-to-noise spectrum of Miranda to synthetic and laboratory spectra of various candidate compounds to shed light on what species may be responsible for the 2.2- $μ$ m band. We conclude that the 2.2- $μ$ m absorption is best matched by a combination of NH $_{3}$ ice with NH $_{3}$ -hydrates or NH $_{3}$ -H $_{2}$ O mixtures. NH $_{4}$ -bearing salts like NH $_{4}$ Cl are also promising candidates that warrant further investigation.

arXiv comment29 pages, 10 figures. Accepted for publication in Planetary Science Journal

Are NH3​ and CO2​ ice present on Miranda?

Abstract

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Are NH $_{3}$ and CO $_{2}$ ice present on Miranda?