** Progress in Earth and Planetary Science is the official journal of the Japan Geoscience Union, published in collaboration with its 51 society members.
** Progress in Earth and Planetary Science is partly financially supported by a Grant-in-Aid for Publication of Scientific Research Results to enhance dissemination of information of scientific research.
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Research
Space and planetary sciences
201706201706
Feasibility of retrieving dust properties and total column water vapor from solar spectra measured using a lander camera on Mars
Manago N, Noguchi K, Hashimoto G L, Senshu H, Otobe N, Suzuki M, Kuze H
Mars atmosphere, Dust particles, Total column water vapor, Direct solar radiation, Scattered solar radiation, Radiative transfer simulation, Inverse analysis
Combined propagation errors of dust model parameters as a function of solar zenith angle (SZA). Panels (a-g) show errors of optical depth (a), effective radius (b) and variance (c) of size distribution, volume mixing ratio of hematite (d), real (e) and imaginary (f) parts of complex refractive index of silicate, and scale height (g). Case 1. w/ all observation parameters, Case 2. w/o DSR, Case 3. w/o aureole, Case 4. w/o forward scattering, Case 5. w/o backward scattering, and Case 6. w/o color ratio. The left and right scales are normalized by the variation range and a priori value, respectively.
Dust and water vapor are important constituents in the Martian atmosphere, exerting significant influence on the heat balance of the atmosphere and surface. We have developed a method to retrieve optical and physical properties of Martian dust from spectral intensities of direct and scattered solar radiation to be measured using a multi-wavelength environmental camera onboard a Mars lander. Martian dust is assumed to be composed of silicate-like substrate and hematite-like inclusion, having spheroidal shape with a monomodal gamma size distribution. Error analysis based on simulated data reveals that appropriate combinations of three bands centered at 450, 550, and 675 nm wavelengths and 4 scattering angles of 3°, 10°, 50°, and 120° lead to good retrieval of four dust parameters, namely, aerosol optical depth, effective radius and variance of size distribution, and volume mixing ratio of hematite. Retrieval error increases when some of the observational parameters such as color ratio or aureole are omitted from the retrieval. Also, the capability of retrieving total column water vapor is examined through observations of direct and scattered solar radiation intensities at 925, 935, and 972 nm. The simulation and error analysis presented here will be useful for designing an environmental camera that can elucidate the dust and water vapor properties in a future Mars lander mission.
