Properties of dust in the Martian atmosphere from the Imager on Mars Pathfinder

Martin G Tomasko, L. R. Doose, M. Lemmon, Peter Smith, E. Wegryn

Research output: Contribution to journalArticle

217 Citations (Scopus)

Abstract

The Imager for Mars Pathfinder (IMP) returned sequences of images of the Martian sky characterizing the size distribution, optical constants, and nature of the aerosols suspended in the atmosphere of Mars. These sequences were executed when the solar elevation angle was approximately 15° and consisted of images near the elevation of the Sun, spanning a range in azimuth from about 4° to 180° from the Sun. Images were obtained at four wavelengths from 444 to 965 nm. From one sequence of observations, results are shown from a comparison of absolute photometry of the Martian sky with multiple scattering models. Results include the following. (1) The geometric cross-section-weighted mean particle radius is 1.6 ± 0.15 μm almost independent of the assumed width (variance) of the size distribution. (2) The imaginary refractive index shows a steep increase with wavelength from 670 nm to shorter wavelengths, and a shallow increase toward longer wavelengths, consistent with the reflection spectrum observed by IMP for Martian soil. (3) For each assumed variance, two parameters governing the slope and curvature of the portion of the phase function due to internally transmitted light are found uniquely as functions of wavelength. (4) The variance of the gamma size distribution is difficult to constrain from these observations alone. The shape of the single scattering phase functions derived from the IMP observations is compared to laboratory measurements of powder samples. One sample of irregular particles has a single scattering phase function quite similar to that derived for Mars. Overall, the results for the mean cross-section-weighted size and imaginary refractive index as a function of wavelength are in remarkably good agreement with the revised analysis by Pollack et al. [1995] of the observations made by the Viking lander 20 years earlier.

Original languageEnglish (US)
Pages (from-to)8987-9007
Number of pages21
JournalJournal of Geophysical Research: Space Physics
Volume104
Issue numberE4
StatePublished - Apr 25 1999

Fingerprint

Mars Pathfinder
Martian atmosphere
Image sensors
Dust
dust
wavelength
atmospheres
Wavelength
wavelengths
scattering
refractive index
Sun
mars
sky
Mars
Refractive index
sun
cross section
Scattering
refractivity

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Atmospheric Science
  • Geochemistry and Petrology
  • Geophysics
  • Oceanography
  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Properties of dust in the Martian atmosphere from the Imager on Mars Pathfinder. / Tomasko, Martin G; Doose, L. R.; Lemmon, M.; Smith, Peter; Wegryn, E.

In: Journal of Geophysical Research: Space Physics, Vol. 104, No. E4, 25.04.1999, p. 8987-9007.

Research output: Contribution to journalArticle

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