Isotopic fractionation through water vapor condensation: The Deuteropause, a cold trap for deuterium in the atmosphere of Mars

Bertaux, Jean-Loup; Montmessin, Franck

doi:10.1029/2000je001358

Cited by 55 publications

(71 citation statements)

References 21 publications

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“…HDO and H 2 O are fractionated by condensation and by photolysis (e.g. Bertaux and Montmessin 2001), hence their distribution is an indication of cloud formation.…”

Section: Water Cyclementioning

confidence: 99%

NOMAD, an Integrated Suite of Three Spectrometers for the ExoMars Trace Gas Mission: Technical Description, Science Objectives and Expected Performance

Vandaele¹,

Moreno²,

Patel³

et al. 2018

Space Sci Rev

114

117

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The NOMAD ("Nadir and Occultation for MArs Discovery") spectrometer suite on board the ExoMars Trace Gas Orbiter (TGO) has been designed to investigate the comThis paper is dedicated to the memory of M. Allen, V. Formisano, and J. McConnell. position of Mars' atmosphere, with a particular focus on trace gases, clouds and dust. The detection sensitivity for trace gases is considerably improved compared to previous Mars missions, compliant with the science objectives of the TGO mission. This will allow for a major leap in our knowledge and understanding of the Martian atmospheric composition and the related physical and chemical processes. The instrument is a combination of three spectrometers, covering a spectral range from the UV to the mid-IR, and can perform solar occultation, nadir and limb observations. In this paper, we present the science objectives of the instrument and explain the technical principles of the three spectrometers. We also discuss the expected performance of the instrument in terms of spatial and temporal coverage and detection sensitivity.

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“…HDO and H 2 O are fractionated by condensation and by photolysis (e.g. Bertaux and Montmessin 2001), hence their distribution is an indication of cloud formation.…”

Section: Water Cyclementioning

confidence: 99%

NOMAD, an Integrated Suite of Three Spectrometers for the ExoMars Trace Gas Mission: Technical Description, Science Objectives and Expected Performance

Vandaele¹,

Moreno²,

Patel³

et al. 2018

Space Sci Rev

114

117

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“…On a global scale, the disk-integrated estimate of this ratio, compared with its value in past measurements in the most ancient SNC meteorites and/or in clays at the Martian surface is a tracer of the abundance of the early content of water on Mars (Greenwood et al 2008;Mahaffy et al 2015). Indeed, the main mechanism responsible for the deuterium enrichment in the Martian atmosphere is expected to be fractionation through differential escape rates, the HDO molecule being heavier than H 2 O and confined at low altitude by condensation (Bertaux & Montmessin 2001).…”

Section: Introductionmentioning

confidence: 99%

A map of D/H on Mars in the thermal infrared using EXES aboard SOFIA

Encrenaz

DeWitt

Richter

et al. 2016

A&A

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On a planetary scale, the D/H ratio on Mars is a key diagnostic for understanding the past history of water on the planet; locally, it can help to constrain the sources and sinks of water vapor through the monitoring of condensation and sublimation processes. To obtain simultaneous measurements of H 2 O and HDO lines, we have used the Echelle Cross Echelle Spectrograph (EXES) instrument aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) facility to map the abundances of these two species over the Martian disk. High-resolution spectra (R = 6 × 10 4 ) were recorded in the 1383−1390 cm −1 range (7.2 µm) on April 08, 2014. Mars was very close to opposition and near northern summer solstice (Ls = 113• ). Maps of the H 2 O and HDO mixing ratios were retrieved from the line depth ratios of weak H 2 O and HDO transitions divided by a weak CO 2 line. As expected for this season, the H 2 O and HDO maps show a distinct enhancement toward polar regions, and their mixing ratios are consistent with previous measurements and with predictions by the global climate models, except at the north pole where the EXES values are weaker. We derive a diskintegrated D/H ratio of 6.8 (+1.6, −1.0) × 10 −4 . It is higher than the value in Earth's oceans by a factor 4.4 (+1.0, −0.6). The D/H map also shows an enhancement from southern to northern latitudes, with values ranging from about 3.5 times to 6.0 times the VSMOW (Vienna standard mean ocean water) value. The D/H distribution shows a depletion over the Tharsis mountains and is consistent with observed latitudinal variations. The variations in D/H with latitude and altitude agree with the models and with the isotope fractionation expected from condensation and sublimation processes.

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“…This enrichment of d over h is largely the result of photochemical processes that preferentially dissociate h 2 O relative to hdO and the lower efficiency for the escape of d relative to h at the exobase (where the atmosphere merges into space). In addition, Fouchet and Lellouch [2000] and Bertaux and Montmessin [2001] point out that there is a trap for deuterium on Mars due to water vapor condensation. The latter authors name this the "deuteropause", by analogy with the tropopause in the terrestrial atmosphere [Moyer et al, 1996;Kuang et al, 2003].…”

Section: Atmospheric Chemistry and Atmospheric Evolutionmentioning

confidence: 99%