The Deuterium Isotopic Ratio of Water Released From the Martian Caps as Measured With TGO/NOMAD

Abstract

The evolution and history of water on Mars plays a key role in the assessment of the habitability of the planet across time. There is abundant geomorphological evidence suggesting that Mars had a wetter past (Bibring et al., 2006;Carr & Head, 2003), yet the duration and extent of this more humid past remains a topic of substantial debate. For instance, the large deltas, basins, and valleys on Mars are suggestive of large bodies of water that were stable over relatively long periods of time. Some estimates suggest past volumes of water in excess of a 500 m deep Global Equivalent Layer (GEL; Carr & Head, 2003), which is many times larger than the current estimates of labile water on Mars (∼30 m, Lasue et al., 2013).The large enrichments of D/H measured in atmospheric water suggest that a large fraction, beyond 80%, of this water was lost over time (Jakosky, 2021;Villanueva et al., 2015), and Ar and O isotopic ratios measured with MAVEN (Jakosky et al., 2017) and TGO (Alday, Wilson, et al., 2021) indicate that Mars has lost a large fraction of its atmosphere. Because Mars is less massive than Earth, the neutral escape of volatiles is easier on Mars, considering the similar equilibrium temperatures of the two planets, although Mars is obviously colder. Recent results indicate that most of this escape occurred via neutral and nonionized processes (Brain et al., 2015), in which temperature and its variability across geological times were key factors defining the state of the Martian atmosphere. Recent results from dust storms suggest that dust storms can greatly heat the atmosphere, leading to the upward transport and more readily escape of water (

Global Vertical Distribution of Water Vapor on Mars: Results From 3.5 Years of ExoMars‐TGO/NOMAD Science Operations

“…As for the third source of the additional errors, the most dominant factor is the characterization of the AOTF transfer function. Villanueva et al (2022) showed that the light from nearby orders reaches detectors through the AOTF. By the solar calibration measurements, these signals from nearby orders are quantified for each diffraction order (Villanueva et al, 2022).…”

“…Villanueva et al (2022) presents the up-to-date calibration of the NOMAD SO channel, which has been extensively improved from the earlier studies. The major updates presented in Villanueva et al (2022) are new characterization of (a) Instrumental line shape (ILS), and (b) AOTF transfer function. Villanueva et al (2022) showed that ILS is not an ideal Gaussian function but can be characterized by a sum of two Gaussian functions, whose parameters for each pixel are determined from the measurements of the Mars atmosphere.…”

Variations in Vertical CO/CO2 Profiles in the Martian Mesosphere and Lower Thermosphere Measured by the ExoMars TGO/NOMAD: Implications of Variations in Eddy Diffusion Coefficient

“…Recently, the calibration of the SO channel has been extensively updated (Villanueva et al., 2022). In this update, the AOTF transfer function has been reevaluated using inflight solar measurements, which allows us to significantly reduce the uncertainty and perform the molecular retrievals properly (Villanueva et al., 2022). The characterization of the instrumental line shape (ILS) has also been updated.…”

“…The characterization of the instrumental line shape (ILS) has also been updated. It was found that the ILS is not a simple Gaussian function but has an asymmetric shape (Thomas et al., 2021) that can be reproduced by a combination of two Gaussian functions (Villanueva et al., 2022). These latest updated instrumental functions were used in this analysis.…”

“…NOMAD SO measures spectra from the Mars near-surface to 250 km altitude, and CO and CO 2 absorption features appear below about 100 and 180 km altitudes, respectively. significantly reduce the uncertainty and perform the molecular retrievals properly (Villanueva et al, 2022). The characterization of the instrumental line shape (ILS) has also been updated.…”