Presentation Information
[PPS07-P09]Detection of global thermal tides in Martian surface pressure using OMEGA/Mars Express
Akira Kazama1, Shohei Aoki2,1, Aymeric Spiga3, Tanguy Bertrand4,5, Mathieu Vincendon6, Yann Leseigneur7, Thomas Gautier7,4, *Yasumasa Kasaba1, Hiromu Nakagawa1, Isao Murata1, Takeshi Imamura2, Franck Montmessin7 (1.Tohoku University, 2.University of Tokyo, 3.LMD/IPSL, Sorbonne Université, 4.LIRA, Observatoire de Paris, 5.LPN, CNRS, 6.Institut d’Astrophysique Spatiale, 7.LATMOS/IPSL)
Keywords:
Mars,thermal tides,surface pressure,OMEGA/Mars Express
Thermal tides in the Martian atmosphere are phenomena that link solar radiative heating with atmospheric dynamics and play a key role in shaping the global circulation and dust transport. Because thermal tides have clear diurnal variations in surface pressure, observations of surface pressure provide one of the most direct means of the coupling between radiative forcing and atmospheric dynamics on Mars. Although the presence of thermal tides has been locally detected by landed missions such as Viking, InSight, and Perseverance (e.g., Sánchez-Lavega et al., 2022; Banfield et al., 2020; Zurek et al., 1992), these measurements are limited to discrete locations, and our understanding of their global spatial structure and seasonal dependence has relied on predictions from general circulation models (GCMs).
In this study, we aim to observationally characterize the global properties of Martian thermal tides by retrieving surface pressure from wide-view orbital observations. We use data from the near-infrared imaging spectrometer OMEGA onboard Mars Express to retrieve the global distribution of surface pressure over about three Martian years (MY27–MY29), and to analyze its seasonal and diurnal variations.
Previous remote-sensing studies of surface pressure (e.g., Forget et al., 2007; Spiga et al., 2007) were restricted to limited time periods and relied on externally prescribed dust conditions. In contrast, we extend the analysis period and adopt a method that incorporates dust optical depth simultaneously retrieved from the same OMEGA observations (Kazama et al., 2025) into the surface pressure retrieval. The relative uncertainty of the retrieved surface pressure is estimated to be ±2.5%, which is sufficient to resolve surface pressure variations associated with thermal tides, whose typical amplitudes are on the order of ~5% (e.g., Banfield et al., 2020).
We applied this method to OMEGA observations with good spectral quality (ORB0006–5320; late MY26 to mid-MY29) to retrieve the global distribution and seasonal variation of surface pressure. The results reveal a global seasonal pattern in which surface pressure increases during northern spring and autumn and decreases during summer and winter in each Martian year, with a retrieved pressure amplitude of ~25%. This behavior reflects the seasonal condensation–sublimation cycle of atmospheric CO2 at the polar caps and is consistent with observations from multiple landed missions (Tillman et al., 1993).
Furthermore, by removing the seasonal component and extracting the diurnal variation, we achieved the detection of the latitudinal and seasonal dependence of thermal tides based on wide-view orbital observations. During northern spring and summer, when dust activity is relatively weak, the observed thermal tide amplitudes are generally consistent with predictions from the Mars Climate Database version 6.1 (MCD v6.1; Forget et al., 1999; Millour et al., 2022). In contrast, during northern autumn and winter, when dust activity is enhanced, significantly amplified tidal amplitudes were detected, particularly at low to mid-latitudes in the southern hemisphere, exceeding GCM predictions by up to ~10%. This discrepancy suggests that enhanced atmospheric heating due to increased dust loading may intensify thermal tide forcing beyond what is represented in current GCMs. The detected tidal amplitudes are comparable to or greater than those observed in-situ by the InSight lander (∼4%), supporting the realism of the thermal tide signals captured by the OMEGA-based surface pressure retrieval.
In this presentation, we report the global seasonal variation of Martian surface pressure retrieved from OMEGA observations and discuss the structure of thermal tides that is revealed observationally for the first time in this study.
In this study, we aim to observationally characterize the global properties of Martian thermal tides by retrieving surface pressure from wide-view orbital observations. We use data from the near-infrared imaging spectrometer OMEGA onboard Mars Express to retrieve the global distribution of surface pressure over about three Martian years (MY27–MY29), and to analyze its seasonal and diurnal variations.
Previous remote-sensing studies of surface pressure (e.g., Forget et al., 2007; Spiga et al., 2007) were restricted to limited time periods and relied on externally prescribed dust conditions. In contrast, we extend the analysis period and adopt a method that incorporates dust optical depth simultaneously retrieved from the same OMEGA observations (Kazama et al., 2025) into the surface pressure retrieval. The relative uncertainty of the retrieved surface pressure is estimated to be ±2.5%, which is sufficient to resolve surface pressure variations associated with thermal tides, whose typical amplitudes are on the order of ~5% (e.g., Banfield et al., 2020).
We applied this method to OMEGA observations with good spectral quality (ORB0006–5320; late MY26 to mid-MY29) to retrieve the global distribution and seasonal variation of surface pressure. The results reveal a global seasonal pattern in which surface pressure increases during northern spring and autumn and decreases during summer and winter in each Martian year, with a retrieved pressure amplitude of ~25%. This behavior reflects the seasonal condensation–sublimation cycle of atmospheric CO2 at the polar caps and is consistent with observations from multiple landed missions (Tillman et al., 1993).
Furthermore, by removing the seasonal component and extracting the diurnal variation, we achieved the detection of the latitudinal and seasonal dependence of thermal tides based on wide-view orbital observations. During northern spring and summer, when dust activity is relatively weak, the observed thermal tide amplitudes are generally consistent with predictions from the Mars Climate Database version 6.1 (MCD v6.1; Forget et al., 1999; Millour et al., 2022). In contrast, during northern autumn and winter, when dust activity is enhanced, significantly amplified tidal amplitudes were detected, particularly at low to mid-latitudes in the southern hemisphere, exceeding GCM predictions by up to ~10%. This discrepancy suggests that enhanced atmospheric heating due to increased dust loading may intensify thermal tide forcing beyond what is represented in current GCMs. The detected tidal amplitudes are comparable to or greater than those observed in-situ by the InSight lander (∼4%), supporting the realism of the thermal tide signals captured by the OMEGA-based surface pressure retrieval.
In this presentation, we report the global seasonal variation of Martian surface pressure retrieved from OMEGA observations and discuss the structure of thermal tides that is revealed observationally for the first time in this study.