Titania's Deuterium Abundance and the Origin of Its Water

Tegler, Stephen and Cartwright, Richard and Grundy, William and Holler, Bryan and Burris, William and Loeffler, Mark and Glein, Christopher and Wochner, Ryan and Hemmelgarn, Samantha Titania's Deuterium Abundance and the Origin of Its Water. Planetary Science Journal. ISSN 2632-3338 (Submitted)

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Abstract

Models of our Solar System's protoplanetary disk account for processes such as the infall of water-ice-rich grains from the surrounding molecular cloud, the reprocessing of some infalling water-ice in the hot inner disk, and water's outward migration in the disk. These models predict deuterium abundance in water as a function of heliocentric distance. The James Webb Space Telescope (JWST) enables us to test these models by measuring the abundance of deuterium on icy outer Solar System bodies through spectroscopic observations of the semi-heavy water (HDO) band near 4.1 micron. However, a hurdle to measuring deuterium abundances from JWST spectra is the lack of optical constants for HDO. Here, we present the first optical constants for HDO and new optical constants for H2O. In addition, we combine the optical constants, a radiative transfer model, and a JWST spectrum of the Uranian satellite Titania to measure its deuterium abundance in water, finding D/(H+D) = (2.8 +/- 0.5) x 10^4 in agreement with the model by Yang et al. (2013). Using a simple model, we estimate that most of Titania's water originated from thermally processed inner-disk water, and only a minor portion came from inherited molecular-cloud water. By combining our Titania measurement with Saturnian satellite and comet measurements in the literature, we suggest that outer-satellite water came from a more homogeneous reservoir than comets, and perhaps accreted over a shorter time interval than comets. Furthermore, Titania's deuterium abundance suggests that it formed in a lower-temperature, hydrogen-poor circumplanetary disk rather than a higher-temperature, hydrogen-rich disk.

Item Type:	Article
Subjects:	Q Science > QB Astronomy Q Science > QC Physics Q Science > QD Chemistry
NAU Depositing Author Academic Status:	Faculty/Staff
Department/Unit:	College of the Environment, Forestry, and Natural Sciences > Physics and Astronomy
Date Deposited:	13 May 2026 17:28
Last Modified:	13 May 2026 17:28
URI:	https://openknowledge.nau.edu/id/eprint/6359

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