Comparison of the Reflectivity and Color of Bright and Dark Regions on the Surface of Mars

McCord, T. B.

doi:10.1086/149948

Cited by 14 publications

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“…= 1(3.1 #)/1(2.2 #). There has been much discussion and speculation about the likelihood that compositional and/or particle size variations contribute to the striking albedo changes that define the prominent markings on Mars [e.g., Adams and McCord, 1969;Binder and Jones, 1972;McCord, 1969;Salisbury and Hunt, 1969]. If such variations exist, they might be reflected in the variability of the hydrate absorption band near 3 •t, as was suggested by Sinton [1967].…”

Section: This Difference Seen Inmentioning

confidence: 99%

Evidence about hydrate and solid water in the Martian surface from the 1969 Mariner Infrared Spectrometer

Pimentel¹,

Forney²,

Herr³

1974

J. Geophys. Res.

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The Mariner Mars 6 and 7 infrared spectrometer spectra of Mars include a broad absorption near 3 μ that can be ascribed to water of hydration in the surface minerals and/or ice. Laboratory experiments show that an increase in either form of condensed phase water is accompanied by a decreased intensity ratio R1 = I(3.10 μ)/I(2.20 μ). Evidence for the presence of ice is provided by the intensity ratio R2 = I(2.90 μ)/I(3.10 μ) since R2 is below unity for silicate hydrates and exceeds unity for ice. Near the Martian equator both the surface temperature and R1depend inversely upon brightness at 2.2 μ: a doubling of B(2.2 μ) is accompanied by a 19° temperature drop and a 30% drop in R1. BothR1 and R2 depend upon latitude: R1 is low near the equator and at latitudes more southerly than 50°S, whereas R1 is high in between. These data show that condensed phase water is present throughout the observed surface of Mars, the brighter areas near the equator (and north of it) and the regions south of 50°S being the most hydrated. All three variables, B(2.2), R1, and R2, change dramatically and in concert in a 5° latitude range at the polar cap edge. The characteristic spectral signature of ice can be discerned as well, indicating that ice is forming in this region, most likely on the planetary surface.

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Section: This Difference Seen Inmentioning

confidence: 99%

Evidence about hydrate and solid water in the Martian surface from the 1969 Mariner Infrared Spectrometer

Pimentel¹,

Forney²,

Herr³

1974

J. Geophys. Res.

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“…Spectra from surfaces of differing spectral contrast that are near each other both in elevation and lateral distance may be ratioed to cancel atmospheric components and produce a ratio–surface spectrum [e.g., McCord , 1969; McCord and Westphal , 1971; Pollack et al , 1990; Moersch et al , 1997; Hoefen et al , 2003; Johnson et al , 2002b; Ruff and Christensen , 2002; Mustard et al , 2005]. If properly applied, the advantage of this technique is the lack of residual atmospheric features in the derived ratio spectrum.…”

Section: Introductionmentioning

confidence: 99%

Global spectral classification of Martian low‐albedo regions with Mars Global Surveyor Thermal Emission Spectrometer (MGS‐TES) data

2007

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Martian low‐albedo surfaces (defined here as surfaces with Mars Global Surveyor Thermal Emission Spectrometer (MGS‐TES) albedo values ≤0.15) were reexamined for regional variations in spectral response. Low‐albedo regions exhibit spatially coherent variations in spectral character, which in this work are grouped into 11 representative spectral shapes. The use of these spectral shapes in modeling global surface emissivity results in refined distributions of previously determined global spectral unit types (Surface Types 1 and 2). Pure Type 2 surfaces are less extensive than previously thought, and are mostly confined to the northern lowlands. Regional‐scale spectral variations are present within areas previously mapped as Surface Type 1 or as a mixture of the two surface types, suggesting variations in mineral abundance among basaltic units. For example, Syrtis Major, which was the Surface Type 1 type locality, is spectrally distinct from terrains that were also previously mapped as Type 1. A spectral difference also exists between southern and northern Acidalia Planitia, which may be due in part to a small amount of dust cover in southern Acidalia. Groups of these spectral shapes can be averaged to produce spectra that are similar to Surface Types 1 and 2, indicating that the originally derived surface types are representative of the average of all low‐albedo regions.

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“…New data [McCord, 1969;McCord and Adams, 1969] give well defined geometric albedo curves from 0.4 to 1.1 /• for the bright areas of Mars and for the dark area Syrtis Major. Seasonal changes in the curve for Syrtis Major were also measured.…”

Section: Introductionmentioning

confidence: 99%

Mars: Interpretation of spectral reflectivity of light and dark regions

Adams¹,

McCord²

1969

J. Geophys. Res.

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119

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New spectral reflectivity curves for the light and dark areas of Mars and for seasonal changes of the dark regions were modeled in the laboratory. Light areas are more oxidized and are probably composed of finer particles than the dark areas. Curves for both regions indicate a combination of ferric iron oxide and mafic silicate rock such as basalt. Seasonal changes in the spectral reflectivity of Syrtis Major are not compatible with wind transport of materials or with surface chemical changes. Models of local seasonal condensation of ice or moisture or of growth of macroscopic very dark gray vegetation satisfy the spectral data.

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Comparison of the Reflectivity and Color of Bright and Dark Regions on the Surface of Mars

Cited by 14 publications

References 0 publications

Evidence about hydrate and solid water in the Martian surface from the 1969 Mariner Infrared Spectrometer

Evidence about hydrate and solid water in the Martian surface from the 1969 Mariner Infrared Spectrometer

Global spectral classification of Martian low‐albedo regions with Mars Global Surveyor Thermal Emission Spectrometer (MGS‐TES) data

Mars: Interpretation of spectral reflectivity of light and dark regions

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