The Distinct and Surprisingly Diverse Populations and Properties of Mars Mesospheric Aerosols

Abstract : Analysis of a 2009-2016 set of MRO CRISM limb observations and contemporaneous MCS and MARCI observations yields a new and uniquely comprehensive characterization of dust and ice aerosol distributions and physical characteristics in the Mars mesosphere (50-100 km). Key conclusions are: [1] very distinct aphelion (Ls=0-160º) and perihelion (Ls=160-360º) aerosol populations, in which low latitude CO2 clouds at 60-70 km altitudes dominate the aphelion mesosphere and H2O ice clouds at 50-75 km altitudes dominate the perihelion mesosphere; [2] mesospheric H2O clouds composed of small particle sizes (Reff=0.2 μm) and CO2 cloud particles exhibiting a very broad range of particle sizes (Reff=0.3-2.5 μm) with small particle sizes prominent at the latitude/altitude boundaries of mesospheric CO2 cloud formation; [3] infrequent mesospheric dust aerosols in these non-planet encircling dust storm years with small particle sizes (Reff=0.3-0.6 μm); [4] MCS temperature measurements indicating saturation conditions in the vicinity of mesospheric ice aerosols and enhanced solar heating in the presence of dust aerosols; [5] very narrow CO2 particle size distributions (Veff=0.01-0.03) indicative of iridescence and rapid, uniform cloud nucleation; [6] MCS-CRISM comparisons indicating comparable daytime (3pm) CO2 cloud particle sizes but also MCS nighttime (3am) measurements indicating pervasive low latitude mesospheric CO2 clouds at lower altitudes (55-65 km) and with larger particle sizes (Reff=4-6 μm); [7] MARCI imaging of mesospheric ice clouds displaying wave forms indicative of gravity-wave forcing; and [8] strong indications that cloud nucleation centers, whatever they may be, are not lacking in Mars' mesosphere.
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Submitted on : Wednesday, February 27, 2019 - 11:54:52 AM
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R. T. Clancy, M. J. Wolff, Michael D. Smith, Armin Kleinboehl, B. A. Cantor, et al.. The Distinct and Surprisingly Diverse Populations and Properties of Mars Mesospheric Aerosols. American Geophysical Union, Fall Meeting 2018, Dec 2018, Washington, United States. pp.abstract #P32B-01. ⟨insu-02050645⟩

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