Impact of gradients at the Martian terminator on the retrieval of ozone from TGO/NOMAD-UVIS
- 1Belgian Institute for Space Aeronomy (BIRA-IASB), Planetary Atmospheres, Uccle, Brussels, Belgium (arianna.piccialli@aeronomie.be)
- 2Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA)
- 3Open University, UK,
- 4NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States
- 5Space Science Institute, Boulder, Colorado, USA
- 6INAF, Istituto di Astrofisica e Planetologia Spaziali, Italy
- 7IAA/CSIC, Granada, Spain
We will investigate the impact of day-night temperature and compositional gradients at the Martian terminator on the retrieval of vertical profiles of ozone obtained from NOMAD-UVIS solar occultations.
Rapid variations in species concentration at the terminator have the potential to cause asymmetries in the species distributions along the line of sight of a solar occultation experiment. Ozone, in particular, displays steep gradients across the terminator of Mars due to photolysis [1]. Nowadays, most of the retrieval algorithms for solar and stellar occultations rely on the assumption of a spherically symmetrical atmosphere. However, photo-chemically induced variations near sunrise/sunset conditions need to be taken into account in the retrieval process in order to prevent inaccuracies.
NOMAD (Nadir and Occultation for MArs Discovery) is a spectrometer composed of 3 channels: 1) a solar occultation channel (SO) operating in the infrared (2.3-4.3 μm); 2) a second infrared channel LNO (2.3-3.8 μm) capable of doing nadir, as well as solar occultation and limb; and 3) an ultraviolet/visible channel UVIS (200-650 nm) that can work in the three observation modes [2,3].
The UVIS channel has a spectral resolution <1.5 nm. In the solar occultation mode, it is mainly devoted to study the climatology of ozone and aerosols [4,5,6].
Since the beginning of operations, on 21 April 2018, NOMAD-UVIS acquired more than 8000 solar occultations with an almost complete coverage of the planet.
NOMAD-UVIS spectra are simulated using the line-by-line radiative transfer code ASIMUT-ALVL developed at IASB-BIRA [7]. In a preliminary study based on SPICAM-UV solar occultations (see [8]), ASIMUT was modified to take into account the atmospheric composition and structure at the day-night terminator. As input for ASIMUT, we used gradients predicted by the 3D GEM-Mars v4 Global Circulation Model (GCM) [9,10].
References
[1] Lefèvre, F., Bertaux, J.L., Clancy, R. T., Encrenaz, T., Fast, K., Forget, F., Lebonnois, S., Montmessin, F., Perrier, S., Aug. 2008. Heterogeneous chemistry in the atmosphere of Mars. Nature 454, 971–975.
[2] Vandaele, A.C., et al., Planetary and Space Science, Vol. 119, pp. 233–249, 2015.
[3] Neefs, E., et al., Applied Optics, Vol. 54 (28), pp. 8494-8520, 2015.
[4] M.R. Patel et al., In: Appl. Opt. 56.10 (2017), pp. 2771–2782. DOI: 10.1364/AO.56.002771.
[5] M.R. Patel et al., In: JGR (Planets), Vol. 126, Is. 11, 2021.
[6] Khayat, Alain S. J., et al., In: JGR (Planets), Vol. 126, Is. 11, 2021.
[7] Vandaele, A.C., et al., JGR, 2008. 113 doi:10.1029/2008JE003140.
[8] Piccialli, A., Icarus, submitted.
[9] Neary, L., and F. Daerden (2018), Icarus, 300, 458–476, doi:10.1016/j.icarus.2017.09.028.
[10] Daerden et al., 2019, Icarus 326, https://doi.org/10.1016/j.icarus.2019.02.030
How to cite: Piccialli, A., Vandaele, A. C., Neary, L., Willame, Y., Aoki, S., Trompet, L., Depiesse, C., Viscardy, S., Daerden, F., Erwin, J., Thomas, I. R., Ristic, B., Mason, J. P., Patel, M., Khayat, A., Wolff, M., Bellucci, G., and Lopez-Moreno, J. J.: Impact of gradients at the Martian terminator on the retrieval of ozone from TGO/NOMAD-UVIS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12125, https://doi.org/10.5194/egusphere-egu22-12125, 2022.
