Martian CO<sub>2</sub> Ice Observation at High Spectral Resolution With ExoMars/TGO NOMAD

D’Aversa, E.; Bellucci, Giancarlo; Carrozzo, F. G.; Lozano, Luca Ruiz; Altieri, F.; Thomas, Ian; Karatekin, Özgür; Mermy, Guillaume Cruz; Schmidt, Frédéric; Robert, Séverine; Vandaele, A. C.; Daerden, Frank; Ristic, Bojan; Patel, Manish R.; López-Moreno, J. J.; Sindoni, G.

doi:10.1029/2021je007083

Cited by 9 publications

(18 citation statements)

References 92 publications

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“…Another instrument that recently documented cap edges and dust storm influence was LNO\NOMAD on Exomars TGO (Cruz Mermy et al, 2022). LNO observed ices in very high resolution (λ/∆λ around 10000) narrow band around 2.335 µm, adding data to the record of IR observations (Oliva et al, 2022). This dataset confirmed OMEGA results, documented MY34 cap edges and impact of GDS, and reported possible detections of CO 2 ice clouds.…”

Section: Introductionsupporting

confidence: 80%

Nine Martian Years of polar caps observations by SPICAM-IR

Lomakin

Fedorova²,

Berdis

et al. 2022

Preprint

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SPICAM-IR, an AOTF spectrometer onboard Mars Express spacecraft with a resolving power of 2,000 covering the spectral range 1-1.7 μm has been observing Mars since 2004. In this wavelength range, it is possible to distinguish between CO2 and H2O ices and measure their band depths. We obtained about 200,000 high-fidelity spectra of CO2 ice in different seasons and locations over the Martian polar caps. The spectra have been associated with slab ice, fine-grained ice, permanent caps, and dark and dirty ice at the cryptic region of the south polar cap. Also, we observed more than 200,000 water ice spectra, specifically its broad feature around 1.5 μm. Water ice is present at the surface or in the atmosphere resulting in a variety of different band depths, often in combination with the CO2 ice. We mapped the equivalent width of 1.43 μm CO2 ice band and the depth of 1.5 μm water ice band, which are the proxies for grain size, and followed their seasonal evolution. From the maps, we produced the edge (outer crocus line) of the CO2 south and north caps for nine Martian Years. The cap edges evolve similarly through all years and are in good agreement with previous OMEGA/Mars Express observations. We also discuss the impact of the global dust storms on the cap edges. Lastly, we interpret some of the water ice observations as water ice clouds in the aphelion cloud belt and the polar hoods.

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Section: Introductionsupporting

confidence: 80%

Nine Martian Years of polar caps observations by SPICAM-IR

Lomakin

Fedorova²,

Berdis

et al. 2022

Preprint

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“…Nevertheless, it is important to mention that, despite the TES map being filtered to minimise the effect of atmospheric dust and clouds, it still contains surface ice [49], increasing the uncertainty in transitional ice/no-ice regions. As in the case of the Ice Index [43], the discussion coming from the FCI is semi-qualitative and the value that we derive later should not be considered as an actual threshold for ice detection, but rather an indication for abundant frost or dense water ice clouds.…”

Section: Frost and Clouds Index Through The 27 µM Absorption Bandmentioning

confidence: 90%

“…The first step of this work is to identify the water ice spectral features covered by NO-MAD diffraction orders. A brief description of the spectral content and main scientific focus of each available LNO diffraction order is presented in Oliva et al [43], who discussed the capability of the NOMAD infrared nadir channel to detect surface ice by using a spectral ratio with orders 190 (2322.9-2341.5 nm) and 169 (2611.8-2632.7 nm). These two orders allowed estimation of the relative depth of the 2.7 µm absorption band, which is the strongest CO 2 and H 2 O ice absorption band in the LNO spectral range.…”

Section: Data Selectionmentioning

confidence: 99%

“…Regarding the ice reflectance spectra, surface CO 2 ice and H 2 O ice are simulated with effective radii of 100 µm (r eff = 100 µm) (dark/light blue solid lines), while r eff = 7 µm and 10 µm are respectively used for CO 2 ice and H 2 O ice clouds (dark/light blue dashed lines). Conversely, the red solid line represents the dust spectrum with r eff = 1 µm [43]. As highlighted by the vertical dashed green line, order 190 is located on the ice cloud continuum.…”

Section: Data Selectionmentioning

confidence: 99%

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Evaluation of the Capability of ExoMars-TGO NOMAD Infrared Nadir Channel for Water Ice Clouds Detection on Mars

et al. 2022

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As part of the payload of the 2016 ExoMars Trace Gas Orbiter (TGO) mission, the Nadir and Occultation for MArs Discovery (NOMAD) suite instrument has been observing the Martian atmosphere since March 2018. NOMAD is mainly dedicated to the study of trace atmospheric species taking advantage of a high-spectral resolution. We demonstrate that when NOMAD is observing in nadir mode, i.e., when the line-of-sight points to the centre of Mars, it can be also exploited to detect ice. In this study we present a method based on the investigation of nadir observations of the NOMAD infrared channel, acquired during Mars Years 34 and 35 (March 2018 to February 2021). We take advantage of the strong water ice absorption band at 2.7 µm by selecting the diffraction orders 167, 168, and 169. We derive the Frost and Clouds Index (FCI), which is a good proxy for ice mapping, and obtain latitudinal-seasonal maps for water ice clouds. FCI is sensitive to the Polar Hood clouds. Nevertheless, detections in the Aphelion Cloud Belt (ACB) are limited. This is consistent with previous observations showing different physical properties between the two main Martian atmospheric structures and making the ACB less detectable in the infrared. We hence derive the infrared nadir channel sensitivity limit for the detection of these clouds.

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“…The Martian polar caps are the main reservoirs of both H 2 O and CO 2 ices on the surface of the red planet, at the interface between the surface and the atmosphere with an active exchange of volatiles by sublimation/condensation. Their seasonal growth and retreat (e.g., Kieffer et al, 2000;Kieffer & Titus, 2001;Langevin et al, 2005Langevin et al, , 2007Appéré et al, 2011;Calvin et al, 2015Calvin et al, , 2017Oliva et al, 2022) are an important process in both the H 2 O and CO 2 cycles on the present-day Mars, which are two majors features of the global Martian atmospheric circulation (Forget et al, 1999;Montmessin et al, 2017;Titus et al, 2017). Every year, a significant fraction of the atmospheric CO 2 condensates into the seasonal polar caps which results in annual variations of about one-third of the global atmospheric mass (Leighton & Murray, 1966;James et al, 1992;Hourdin et al, 1993Hourdin et al, , 1995Forget, 1998).…”

Section: Introductionmentioning

confidence: 99%