95 research outputs found

    Strong variability of Martian water ice clouds during dust storms revealed from ExoMars Trace Gas Orbiter/NOMAD

    Get PDF
    Observations of water ice clouds and aerosols on Mars can provide important insights into the complexity of the water cycle. Recent observations have indicated an important link between dust activity and the water cycle, as intense dust activity can significantly raise the hygropause, and subsequently increase the escape of water after dissociation in the upper atmosphere. Here present observations from NOMAD/TGO that investigate the variation of water ice clouds in the perihelion season of Mars Year 34 (April 2018‐19), their diurnal and seasonal behavior, and the vertical structure and microphysical properties of water ice and dust. These observations reveal the recurrent presence of a layer of mesospheric water ice clouds subsequent to the 2018 Global Dust Storm. We show that this layer rose from 45 to 80 km in altitude on a timescale of days from heating in the lower atmosphere due to the storm. In addition, we demonstrate that there is a strong dawn dusk asymmetry in water ice abundance, related to nighttime nucleation and subsequent daytime sublimation. Water ice particle sizes are retrieved consistently and exhibit sharp vertical gradients (from 0.1 to 4.0 μm), as well as mesospheric differences between the Global Dust Storm (<0.5 μm) and the 2019 regional dust storm (1.0 μm), which suggests differing water ice nucleation efficiencies. These results form the basis to advance our understanding of mesospheric water ice clouds on Mars, and further constrain the interactions between water ice and dust in the middle atmosphere

    Martian Atmospheric Aerosols Composition and Distribution Retrievals During the First Martian Year of NOMAD/TGO Solar Occultation Measurements: 2. Extended Results, End of MY 34 and First Half of MY 35

    Get PDF
    This is the second part of Stolzenbach et al. (2023, https://doi.org/10.1029/2022JE007276), named hereafter Paper I, extends the period to the end of MY 34 and the first half of MY 35. This encompasses the end phase of the MY 34 Global Dust Storm (GDS), the MY 34 C-Storm, the Aphelion Cloud Belt (ACB) season of MY 35, and an unusual early dust event of MY 35 from LS_S 30° to LS_S 55°. The end of MY 34 overall aerosol size distribution shows the same parameters for dust and water ice to what was seen during the MY 34 GDS. Interestingly, the layered water ice vertical structure of MY 34 GDS disappears. The MY 34 C-Storm maintains condition like the MY 34 GDS. A high latitude layer of bigger water ice particles, close to 1 μm, is seen from 50 to 60 km. This layered structure is linked to an enhanced meridional transport characteristic of high intensity dust event which put the MY 34 C-Storm as particularly intense compared to non-GDS years C-Storms as previously suggested by Holmes et al. (2021, https://doi.org/10.1016/j.epsl.2021.117109). Surprisingly, MY 35 began with an unusually large dust event (Kass et al., 2020, https://ui.adsabs.harvard.edu/abs/2020AGUFMP039…01K) found in the Northern hemisphere during LS_S 35° to LS_S 50°. During this dust event, the altitude of aerosol first detection is roughly equal to 20 km. This is close to the values encountered during the MY 34 GDS, its decay phase and the C-Storm of the same year. Nonetheless, no vertical layered structure was observed

    Martian Atmospheric Aerosols Composition and Distribution Retrievals During the First Martian Year of NOMAD/TGO Solar Occultation Measurements: 1. Methodology and Application to the MY 34 Global Dust Storm

    Get PDF
    Since the beginning of the Trace Gas Orbiter (TGO) science operations in April 2018, its instrument “Nadir and Occultation for MArs Discovery” (NOMAD) supplies detailed observations of the IR spectrums of the Martian atmosphere. We developed a procedure that allows us to evaluate the composition and distribution\u27s parameters of the atmospheric Martian aerosols. We use a retrieval program (RCP) in conjunction with a radiative forward model (KOPRA) to evaluate the vertical profile of aerosol extinction from NOMAD measurements. We then apply a model/data fitting strategy of the aerosol extinction. In this first article, we describe the method used to evaluate the parameters representing the Martian aerosol composition and size distribution. MY 34 GDS showed a peak intensity from LS_S 190° to 210°. During this period, the aerosol content rises multiple scale height, reaching altitudes up to 100 km. The lowermost altitude of aerosol\u27s detection during NOMAD observation rises up to 30 km. Dust aerosols reff_{eff} were observed to be close to 1 μm and its νeff_{eff} lower than 0.2. Water ice aerosols reff_{eff} were observed to be submicron with a νeff_{eff} lower than 0.2. The vertical aerosol structure can be divided in two parts. The lower layers are represented by higher reff_{eff} than the upper layers. The change between the lower and upper layers is very steep, taking only few kilometers. The decaying phase of the GDS, LS 210°–260°, shows a decrease in altitude of the aerosol content but no meaningful difference in the observed aerosol\u27s size distribution parameters

    Independent confirmation of a methane spike on Mars and a source region east of Gale Crater

    Get PDF
    Reports of methane detection in the Martian atmosphere have been intensely debated. The presence of methane could enhance habitability and may even be a signature of life. However, no detection has been confirmed with independent measurements. Here, we report a firm detection of 15.5 ± 2.5 ppb by volume of methane in the Martian atmosphere above Gale Crater on 16 June 2013, by the Planetary Fourier Spectrometer onboard Mars Express, one day after the in situ observation of a methane spike by the Curiosity rover. Methane was not detected in other orbital passages. The detection uses improved observational geometry, as well as more sophisticated data treatment and analysis, and constitutes a contemporaneous, independent detection of methane. We perform ensemble simulations of the Martian atmosphere, using stochastic gas release scenarios to identify a potential source region east of Gale Crater. Our independent geological analysis also points to a source in this region, where faults of Aeolis Mensae may extend into proposed shallow ice of the Medusae Fossae Formation and episodically release gas trapped below or within the ice. Our identification of a probable release location will provide focus for future investigations into the origin of methane on Mars
    corecore