ChemCam Passive Sky Spectroscopy at Gale Crater: Diurnal and Seasonal cycles of O2, H2O, and aerosols

T. H. McConnochie, M. D. Smith, S. C. Bender, M. J. Wolff, J. R. Johnson, M. T. Lemmon, R. C. Wiens, S. Maurice, O. Gasnault, D. L. Blaney, L. P. DeFlores, A. M. Harri, O. Kemppinen, M. Genzer, J. Moores, M. H. Wong, M. G. Trainer, J. Martín-Torres, M. P. Zorzano, H. B. FranzB. L. Barraclough, S. K. Atreya, P. R. Mahaffy, F. Lefèvre, J. Lasue

Research output: Contribution to conferenceAbstractpeer-review


The Mars Science Laboratory's (MSL) ChemCam spectrometer has been measuring atmospheric aerosol properties and gas abundances for more than one Martian year, doing so by operating in passive mode and observing scattered sky light at two different elevation angles. We perform these observations at 1 - 2 week intervals, occasionally acquiring multiple observations on a given day to assess the diurnal cycle. Six parameters are retrieved from each observation: dust aerosol particle effective radius, ice aerosol particle effective radius, the fraction of opacity contributed by ice rather than dust aerosol, the ratio of aerosol extinction scale height to gas pressure scale height (as a parameterization of the aerosol vertical profile), the O2 volume mixing ratio, and the water vapor column abundance (in precipitable microns). The retrieval works by first constructing a ratio of the spectra from the two elevation angles and then fitting a discrete ordinates multiple scattering radiative transfer model. Total column opacity, CO2 mixing ratio, and atmospheric pressure are exogenous inputs. They are sourced from Mastcam, SAM QMS, and REMS measurements, respectively. An important feature of our procedure, which we have verified by numerical experimentation, is that the retrieved gas abundances have negligible sensitivity to the accuracy of the aerosol parameter solutions or to exogenous inputs or to a wide range of model assumptions. We will present a survey of the results from the extensive ChemCam passive sky data set, including comparisons to related SAM and REMS in-situ atmospheric sampling and to Mastcam and Navcam sky observation campaigns. We will show that O2 has temporal variation unexplained by existing photochemical models and has vertical variations within the bottom 10 km of the atmosphere in some seasons. We will also show the water vapor is well mixed within the bottom 10 km in some seasons but not in others, and we will address a variety of aerosol phenomena.

Original languageEnglish
Publication statusPublished - Dec 2015
EventAGU Fall Meeting 2015 - San Francisco, United States
Duration: 14 Dec 201518 Dec 2015


ConferenceAGU Fall Meeting 2015
Country/TerritoryUnited States
CitySan Francisco

Bibliographical note

abstract id.P22A-08


  • 0343 Planetary atmospheres
  • 3346 Planetary meteorology
  • 6225 Mars
  • 5405 Atmospheres


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