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The high-altitude peaks of atmospheric ozone as observed by NOMAD/UVIS onboard the ExoMars Trace Gas Orbiter Mission
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  • Alain SJ Khayat,
  • Michael D. Smith,
  • Michael J. Wolff,
  • Frank W. Daerden,
  • Lori Neary,
  • Manish R Patel,
  • Arianna Piccialli,
  • Ann Carine Vandaele,
  • Ian Richard Thomas,
  • Bojan Ristic,
  • J. Mason,
  • Yannick Willame,
  • Cédric Depiesse,
  • Giancarlo Bellucci,
  • José Juan López-Moreno
Alain SJ Khayat
NASA Goddard Space Flight Center

Corresponding Author:[email protected]

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Michael D. Smith
NASA Goddard Space Flight Center
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Michael J. Wolff
Space Science Institute
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Frank W. Daerden
Royal Belgian Institute for Space Aeronomy BIRA-IASB
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Lori Neary
Royal Belgian Institute for Space Aeronomy BIRA-IASB
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Manish R Patel
The Open University
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Arianna Piccialli
Belgian Institute for Space Aeronomy (BIRA-IASB)
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Ann Carine Vandaele
Royal Belgian Institute for Space Aeronomy
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Ian Richard Thomas
Belgian Institute for Space Aeronomy
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Bojan Ristic
Royal Belgian Institute for Space Aeronomy
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J. Mason
Open University
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Yannick Willame
Belgian Institute For Space Aeronomy
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Cédric Depiesse
Royal Belgian Institute for Space Aeronomy
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Giancarlo Bellucci
Institute for Space Astrophysics and Planetology
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José Juan López-Moreno
Instituto de Astrofisica de Andalucia, IAA-CSIC
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Abstract

Solar occultations performed by the Nadir and Occultation for MArs Discovery (NOMAD) ultraviolet and visible spectrometer (UVIS) onboard the ExoMars Trace Gas Orbiter (TGO) have provided a comprehensive mapping of ozone density, describing the seasonal and spatial distribution of atmospheric ozone in detail. The observations presented here extend over a full Mars year between April 2018 at the beginning of the TGO science operations during late northern summer on Mars (Ls = 163°) and March 2020. UVIS provided transmittance spectra of the martian atmosphere in the 200 - 650 nm wavelength range, allowing measurements of the vertical distribution of the ozone density using its Hartley absorption band (200 – 300 nm). Our findings indicate the presence of (1) a high-altitude peak of ozone between 40 and 60 km in altitude over the north polar latitudes for over 45 % of the martian year, particularly during mid-northern spring, late northern summer-early southern spring, and late southern summer, and (2) a second, but more prominent, high-altitude ozone peak in the south polar latitudes, lasting for over 60 % of the year including the southern autumn and winter seasons. When they are present, both high-altitude peaks are observed in the sunrise and sunset occultations, indicating that the layers could persist during the day. Model results from the GEM-Mars General Circulation predicts the general behavior of the high-altitude peaks of ozone observed by UVIS and are used in an attempt to further our understanding of the chemical processes controlling the high-altitude ozone on Mars.