Total reflection spectrophotometry and thermogravimetric analysis of simulated Martian surface materials

Carl Sagan, Jean P. Phaneuf, Michael Ihnat

The ultraviolet, visible, and near infrared reflection spectra of the Martian bright areas have been compared with the corresponding laboratory reflectivities, measured with an integrating sphere, of a variety of minerals containing ferric oxides and silicates, as solids and in pulverized form. Except in the ultraviolet, where the effects of the Martian blue haze are prominent, pulverized limonite, a ferric oxide polyhydrate, matches the shape and amplitude of the Martian Russell-Bond albedo within experimental and observational error. Further observational tests of this identification are outlined. If water-rich limonite is a primary constituent of the Martian bright areas, conditions in the earlier history of Mars were probably much more equable than contemporary conditions, and the origin and evolution of life on primitive Mars becomes easier to understand. © 1965.

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Materials
Curve 1
Temperature K: ~298 Wavelength Range, µm: 0.517-2.60 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: GOETHITE; solid sample from Biwabik, Minnesota; data extracted from smooth curve; [Authors' designation: Variety 3].
Curve 2
Temperature K: ~298 Wavelength Range, µm: 0.231-2.60 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: GOETHITE; powder from Biwabik, Minnesota; mean particle size 130 µm; data extracted from smooth curve; [Authors' designation: Variety 3].
Curve 3
Temperature K: ~298 Wavelength Range, µm: 0.511-2.60 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: Similar to the above specimen and conditions except sample taken through thermogravimetric analysis to 1473 K with resultant 9.8% mass loss (H₂O); particle size 180 µm.
Curve 4
Temperature K: ~298 Wavelength Range, µm: 0.508-2.60 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: HEMATITE from Ironton, Minnesota; solid sample; data extracted from smooth curve; [Authors' designation: Variety 2].
Curve 5
Temperature K: ~298 Wavelength Range, µm: 0.504-2.56 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: HEMATITE powder from Ironton, Minnesota; mean particle size 10 µm; data extracted from smooth curve; [Authors' designation: Variety 2].
Curve 6
Temperature K: ~298 Wavelength Range, µm: 0.511-2.60 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: Similar to the above specimen and conditions except sample taken through thermogravimetric analysis to 1473 K with resultant <0.3% mass loss; mean particle size 21 µm.
Curve 7
Temperature K: ~298 Wavelength Range, µm: 0.787-2.60 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: LIMONITE, FeO·nH₂O; solid sample from Tuscaloosa, Alabama; data extracted from smooth curve; [Authors' designation: Variety 1].
Curve 8
Temperature K: ~298 Wavelength Range, µm: 0.238-2.60 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: LIMONITE, FeₓOy·nH₂O; powder from Tuscaloosa, Alabama; mean particle size 127 µm; data extracted from smooth curve; [Authors' designation: Variety 1].
Curve 9
Temperature K: ~298 Wavelength Range, µm: 0.516-2.60 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: Similar to the above specimen and conditions except sample taken through thermogravimetric analysis to 1473 K with resultant 10% mass loss (H₂O); mean particle size 131 µm.
Curve 10
Temperature K: ~298 Wavelength Range, µm: 0.488-2.50 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: OOLITIC HEMATITE; solid sample from Chilton, N. Y.; data extracted from smooth curve; [Authors' designation: Variety 5].
Curve 11
Temperature K: ~298 Wavelength Range, µm: 0.490-2.54 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: OOLITIC HEMATITE powder from Chilton, N. Y.; mean particle size 74 µm; data extracted from smooth curve; [Authors' designation: Variety 5].
Curve 12
Temperature K: ~298 Wavelength Range, µm: 0.505-2.60 Geometry θ θ' ω: ~0° 2π Composition (weight percent), Specifications, and Remarks: Similar to the above specimen and conditions except sample taken through thermogravimetric analysis to 1473 K with resultant 19.0% mass loss (CO₂); mean particle size 130 µm.
Curve 1
Temperature K: ~298 Wavelength Range, µm: 0.200-2.60 Geometry θ θ' w: ~0° 2π Composition (weight percent), Specifications, and Remarks: OLIVENE, (Mg, Fe)₂SiO₄; solid sample; data extracted from smooth curve.
Curve 2
Temperature K: ~298 Wavelength Range, µm: 0.200-2.60 Geometry θ θ' w: ~0° 2π Composition (weight percent), Specifications, and Remarks: SERPENTINE CONGLOMERATE, 3MgO·2SiO₂·2H₂O; data extracted from smooth curve.
Curve 3
Temperature K: ~298 Wavelength Range, µm: 0.200-2.60 Geometry θ θ' w: ~0° 2π Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except different different face measured.