Europlanet Science Congress 2021
Virtual meeting
13 – 24 September 2021
Europlanet Science Congress 2021
Virtual meeting
13 September – 24 September 2021
EPSC Abstracts
Vol. 15, EPSC2021-725, 2021
Europlanet Science Congress 2021
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Mesospheric water ice clouds in Mars Year 34-35 as identified in ExoMars UVIS occultation opacities

Paul Streeter1, Graham Sellers1, Mike Wolff2, Jon Mason1, Manish Patel1,3, Stephen Lewis1, James Holmes1, Frank Daerden4, Ian Thomas4, Bojan Ristic4, Yannick Willame4, Cedric Depiesse4, Ann Carine Vandaele4, Giancarlo Bellucci5, and Jose Juan López-Moreno6
Paul Streeter et al.
  • 1The Open University, School of Physical Sciences, Milton Keynes, United Kingdom of Great Britain – England, Scotland, Wales (
  • 2Space Science Institute, Boulder, Colorado, U.S.A.
  • 3Space Science and Technology Department, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX11 0QX, U.K.
  • 4Royal Belgian Institute for Space Aeronomy (IASB-BIRA), Brussels, Belgium
  • 5Instituto de Astrofisica e Planetologia Spaziali (IAPS/INAF), Rome, Italy
  • 6Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain

Introduction:  Suspended atmospheric aerosols are key components of the martian atmosphere, and their vertical distribution has long been a subject of investigation with orbital observations and modelling. The aerosols found in Mars' atmosphere are mineral dust, water ice, and CO2 ice, and each have distinct spatiotemporal distributions and radiative effects.

Of particular interest for this study is the vertical distribution of atmospheric aerosols. In recent years, dust has been observed to have a more complex vertical distribution structure than previously thought, with the detection of detached dust layers [1] and large plume-like structures during Global Dust Storms (GDS) [2].

Water ice distribution is tied to the seasonal behaviour of its associated cloud formations, with seasonally recurring features including the aphelion cloud belt (ACB) [3] and polar hood clouds [4] at tropospheric altitudes, as well as higher altitude mesospheric (>40 km) clouds during Mars’ perihelion season [5] as well as during GDS [6,7].

Mars’ low atmospheric temperatures also enable the formation of CO2 ice clouds, which have been detected at mesospheric altitudes over the tropics/subtropics and generally during the colder aphelion season [5,8]. These are thought to be more ephemeral than their water ice counterparts, with lifetimes as low as minutes [9]. More persistent and optically thicker CO2 ice clouds have been detected at tropospheric altitudes in the polar night [10].

 The Ultraviolet and Visible (UVIS) Spectrometer [11], part of the Nadir and Occultation for MArs Discovery (NOMAD) spectrometer suite aboard the ExoMars Trace Gas Orbiter (TGO) [12], has now observed the martian atmospheric limb via solar occultations for over 1.5 martian years. This period covers the 2018/Mars Year (MY) 34 GDS and regional dust storm, as well as the entirety of the more typical MY 35. As such, UVIS solar occultation data provides a great opportunity to examine Mars’ vertical aerosol structure.

Results: We present a new UVIS occultation opacity profile dataset, openly available for use by the community. We also discuss particular features of interest in the dataset, and interpret these features by reference to previous published work and by comparison with the MGCM. In particular, we focus on notable mesospheric water ice cloud phenomena observed in both MY 34 and MY 35. We describe the spatiotemporal distribution of these features, and the link between specific water ice features and strong atmospheric dust activity from global and regional storms. The MGCM temperature and aerosol opacity fields provide valuable points of comparison with the UVIS dataset, for the purposes of both explanation and validation of the MGCM’s existing parametrizations. The UVIS dataset offers opportunities for further research into the vertical aerosol structure of the martian atmosphere, and improvement of how this is represented in numerical models.

References: [1] Heavens, N. G. et al (2011) JGR (Planets), 116(E4), E04003. [2] Heavens, N. G. et al (2019) GRL, 124(11), 2863-2892. [3] Smith M. D. (2008) Annu. Rev. Earth Planet Sci, 26, 191-219. [4] Wang, H. & Ingersoll, A. P. (2002) JGR (Planets), 107(E10), 8-1-8-16. [5] Clancy, R. T. et al (2019) Icarus, 328, 246-273. [6] Liuzzi G. et al (2020) JGR (Planets), 125(4). [7] Stcherbinine, A. et al (2020) JGR (Planets), 125(3). [8] Aoki, S. et al (2018) Icarus, 302, 175-190. [9] Listowski, C. et al (2014) Icarus, 237, 239-261. [10] Hayne, P. O. et al (2012) JGR (Planets), 117(E8). [11] Patel, M. R. et al (2017) Appl. Opt., 56(10), 2771-2782. [12] Vandaele, A. C. et al (2015) Planet. Space Sci., 119, 233-249.

How to cite: Streeter, P., Sellers, G., Wolff, M., Mason, J., Patel, M., Lewis, S., Holmes, J., Daerden, F., Thomas, I., Ristic, B., Willame, Y., Depiesse, C., Vandaele, A. C., Bellucci, G., and López-Moreno, J. J.: Mesospheric water ice clouds in Mars Year 34-35 as identified in ExoMars UVIS occultation opacities, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-725,, 2021.