First detection of ozone in the mid-infrared at Mars: implications for methane detection

¹ Department of Physics, University of Oxford, Oxford, UK
e-mail: Kevin.Olsen@physics.ox.ac.uk
² Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS/CNRS), Paris, France
³ Space Research Institute (IKI), Moscow, Russia
⁴ Moscow Institute of Physics and Technology, Moscow, Russian Federation

Received: 8 April 2020
Accepted: 22 May 2020

Abstract

Aims. The ExoMars Trace Gas Orbiter was sent to Mars in March 2016 to search for trace gases diagnostic of active geological or biogenic processes.

Methods. We report the first observation of the spectral features of Martian ozone (O₃) in the mid-infrared range using the Atmospheric Chemistry Suite Mid-InfaRed (MIR) channel, a cross-dispersion spectrometer operating in solar occultation mode with the finest spectral resolution of any remote sensing mission to Mars.

Results. Observations of ozone were made at high northern latitudes (>65°N) prior to the onset of the 2018 global dust storm (L_s = 163–193°). During this fast transition phase between summer and winter ozone distribution, the O₃ volume mixing ratio observed is 100–200 ppbv near 20 km. These amounts are consistent with past observations made at the edge of the southern polar vortex in the ultraviolet range. The observed spectral signature of ozone at 3000–3060 cm⁻¹ directly overlaps with the spectral range of the methane (CH₄) ν₃ vibration-rotation band, and it, along with a newly discovered CO₂ band in the same region, may interfere with measurements of methane abundance.