HCl Variability in the Martian Atmosphere observed with ExoMars-TGO/NOMAD during 6 years of Solar Occultations
Notice bibliographique
Résumé
NOMAD [1] (Nadir and Occultation for MArs Discovery) is a multi-channel spectrometer onboard the ExoMars 2016 Trace Gas Orbiter (TGO), which began its observations in April 2018. Among other two (LNO and UVIS), the Solar Occultation (SO) channel covers the infrared (IR) spectrum from 2.3 to 4.3 µm (2320 to 4350 cm-1). Composed of an echelle grating in Litrow configuration, a total of 6 diffraction orders (with a typical width from 20 to 35 cm-1) are selected during each solar occultation using an Acousto-Optical Tunable Filter (AOTF) with a sample rate of about ~1 s, allowing a vertical resolution of typically 1 km. The high spectral resolution (λ/∆λ ~17000) and the relatively low signal to noise ratio of this instrument (~2500) make NOMAD SO suitable for the detection of hydrogen chloride HCl. This trace species, although until now considered to be a negligible compound in the Martian atmosphere [2, 3], it has been detected systematically by two instruments onboard TGO: the Atmospheric Chemistry Suite (ACS) [4] and more recently NOMAD [5]. Several works suggest the surface of Mars to be a source of chloride minerals and perchlorate salts [6], which along with interactions surface-atmosphere could allow for chlorine photochemistry happening on the martian atmosphere. On Earth, one of the main sources of HCl is the volcanic activity [7], so the detection of this species on Mars may be an indicator of active geological processes. Multiple ongoing studies are trying to characterize the climatology of HCl on Mars, currently not completely understood, looking for possible relationships between temperature and other atmospheric species such as dust or water vapor.At the IAA we have carried out a study with the objective of identifying not only sources but seasonal variability of HCl by analyzing NOMAD spectra. This early study [8] using a simplified processing pipeline allowed us to detect HCl during the perihelion season of MYs 34 and 35, confirming previous results from [5]. Here, as a follow-up work of that study, we applied a modified version of our IAA-CSIC NOMAD processing pipeline [9-12] in order to increase the sensitivity required for the detection of weak HCl absorption lines, we have analyzed a total of 2536 solar occultations measured during Martian Years 34, 35 and 36. Among those modifications, we improved the methodology used for the characterization of the spectral continuum, now being able to detect systematic oscillations with amplitudes similar to the measurement noise (10-4 in transmittance). We have performed retrievals using NOMAD spectra from diffraction orders 129 (2899 - 2922 cm-1) and 130 (2921 - 2945 cm-1). In order to obtain robust HCl detections, we used the spectra from three detector bins on each ocucltation, retrieving an independent vertical profile form each bin. We present HCl vertical profiles and the seasonal variability of this species from a climatological view, revealing possible links with water vapor and dust.AcknowledgmentsThe IAA/CSIC team acknowledges financial support from the Severo Ochoa grant CEX2021-001131-S and by grants PID2022-137579NB-I00, RTI2018-100920-J-I00 and PID2022-141216NB-I00 all funded by MCIN/AEI/ 10.13039/501100011033. A. Brines acknowledges financial support from the grant PRE2019-088355 funded by MCIN/AEI/10.13039/501100011033 and by ’ESF Investing in your future’. ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). This project acknowledges funding by the Belgian Science Policy Office (BELSPO), with the financial and contractual coordination by the ESA Prodex Office (PEA 4000103401, 4000121493), by Spanish Ministry of Science and Innovation (MCIU) and by European funds under grants PGC2018-101836-B-I00 and ESP2017-87143-R (MINECO/FEDER), as well as by UK Space Agency through grants ST/V002295/1, ST/V005332/1, ST/Y000234/1 and ST/X006549/1 and Italian Space Agency through grant 2018-2-HH.0. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 101004052. US investigators were supported by the National Aeronautics and Space Administration. Canadian investigators were supported by the Canadian Space Agency. We want to thank M. Vals, F. Montmessin, F. Lefevre, F. Forget and the broad LMD/IPSL team supporting the continuous development of the Mars PCM. References1. Vandaele, A. C. (2018). Space Science Reviews, 214, 1-47.2. Hartogh, P. (2010). Astronomy & Astrophysics, 521, L49.3. Villanueva, G. L. (2013). Icarus, 223(1), 11-27.4. Korablev, O. (2021) . Science Advances 7, eabe4386.5. Aoki, S. (2021). Geophysical Research Letters 48, e2021GL092506.6. Glavin, D. P. (2013). Journal of Geophysical Research: Planets 118, 1955–1973.7. Graedel, T. (1995) . Global Biogeochemical Cycles 9, 47–77.8. Belmote-Gimenez, A. (2023) Mater Thesis, University of Granada.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».