Properties of the Hermean Regolith II. Disk-Resolved Multicolor Photometry and Color Variations of the “Unknown” Hemisphere

Warell, J.

doi:10.1006/icar.2002.6814

Cited by 36 publications

(16 citation statements)

References 43 publications

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“…It is shown below however, that even though using the best-choice representation for the particle angular scattering function the currently available data for the mercurian phase curve remains insufficient to constrain the Hapke parameters uniquely, even in combination with the best ground-based disk-resolved images, due to the large photometric scatter in the data. The situation is even worse when considering the wavelength dependence of the Hapke parameters; though spectroscopic observations have been performed since the 1960's, photometrically usable multiple-wavelength information is available only from SVST image data and this data set is only in part complemented with absolute flux calibration observations (Warell, 2002).…”

Section: Hapke's Photometric Modelmentioning

confidence: 99%

“…Additionally, 650 nm image data, scaled in brightness to the 550 nm reflectance of Mercury, were used to expand the data base. The brightness scaling was based on the calculated geometric albedos at the two wavelenghts from Warell (2002 , Table I). In terms of other sources of error the assumption of constant phase function of the surface from 550 to 650 nm makes a negligible contribution to the total error.…”

Section: Hapke Modellingmentioning

confidence: 99%

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Properties of the Hermean regolith: IV. Photometric parameters of Mercury and the Moon contrasted with Hapke modelling

Warell

2004

Icarus

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Section: Hapke's Photometric Modelmentioning

confidence: 99%

Section: Hapke Modellingmentioning

confidence: 99%

Properties of the Hermean regolith: IV. Photometric parameters of Mercury and the Moon contrasted with Hapke modelling

Warell

2004

Icarus

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“…The dominant geologic units are likely intercrater and smooth plains of predominantly low-iron and low-titanium feldspathic composition, as is the case for the Mariner 10 hemisphere (e.g., Rava & Hapke 1987;Blewett et al 1997). In terms of color contrasts, Warell (2002) found no 940 nm/continuum-band contrast values >2% on better resolved but noisier data from parts of the presently studied hemisphere. Here too, the 950/750 nm ratio image (Fig.…”

Section: Discussionmentioning

confidence: 70%

“…The VISNIR albedo-color distribution of Mercury has been mapped for a region overlapping that studied by Warell (2002). Though some pixel-to-pixel variations attributable to noise are apparent at spatial scales smaller than the seeing-smeared angular resolution, the maps (Fig.…”

Section: Discussionmentioning

confidence: 99%

Albedo–color distribution on Mercury

Warell¹,

Valegård²

2006

A&A

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Aims. The variation of albedo and color of Mercury's surface is studied with disk-resolved image data obtained at six evenly spaced wavelengths in the optical to near infrared wavelength range (447-944 nm) with the 1-m Swedish Solar Telescope on La Palma in April, 2003. Methods. Disk images have been modeled and photometrically normalized with the light scattering theory of Hapke to derive albedocolor properties of a poorly known region (unimaged by Mariner 10) of Mercury's surface between longitudes 210• W and 270• W. Maps of relative abundances of ferrous iron, titanium and optical maturation are derived on the basis of a feldspathic model for the crustal composition and previous results for the Moon, assuming the validity of the general maturation model for mafic silicate regoliths of atmosphereless bodies. Results. The albedo-color scatterplot distributions of Mercury's surface are uniform with respect to wavelength in the near-ultraviolet to near-infrared due to the absence of strong absorption bands in the reflectance spectrum. The extents of the distributions are less than for the global Moon and similar to that of the lunar farside, which is related to the relatively subdued color contrasts of Mercury's primarily feldspathic surface. At the attained 500-km spatial resolution scale, these maps do not indicate the existence of surface regions chemically similar to the lunar maria, which have a high FeO and TiO 2 content. Variations in abundances of ferrous iron and titanium are shown to be less than for the global Moon and similar to the lunar farside at the same spatial scale. Optically bright regions on Mercury are less mature and less opaque than their surroundings consistent with geologically recent immature crater ejecta, while localized dark regions generally have intermediate maturities and iron abundances and higher-than-average titanium abundances. The smaller relative intensity range of spatial variations of spectral parameters in the near infrared compared to the near ultraviolet may imply that relative abundance variations in ferrous iron are smaller than variations in opaque minerals. Conclusions. The results reinforce the similar natures of the Mariner 10-imaged and the poorly known hemispheres of Mercury, as well as their superficial similarity to the lunar farside, and demonstrate that geological interpretation of ground-based observations of albedo features on Mercury is possible.

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“…A similar relationship between spectral slope and emission angle is observed for the Moon, but the relationship is more pronounced in the Mercury observations. Warell's (2002) interpretation is that the regolith of Mercury is more backscattering than the lunar regolith. The more backscattering nature of the surface is also seen in Warell's (2004) modeling of the integral phase curve and CCD images.…”

Section: Physical Properties: Photometrymentioning

confidence: 99%

The Geology of Mercury: The View Prior to the MESSENGER Mission

et al. 2007

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Mariner 10 and Earth-based observations have revealed Mercury, the innermost of the terrestrial planetary bodies, to be an exciting laboratory for the study of Solar System geological processes. Mercury is characterized by a lunar-like surface, a global magnetic field, and an interior dominated by an iron core having a radius at least three-quarters of the radius of the planet. The 45% of the surface imaged by Mariner 10 reveals some distinctive differences from the Moon, however, with major contractional fault scarps and huge expanses of moderate-albedo Cayley-like smooth plains of uncertain origin. Our current image coverage of Mercury is comparable to that of telescopic photographs of the Earth's Moon prior to the launch of Sputnik in 1957. We have no photographic images of one-half of the surface, the resolution of the images we do have is generally poor (∼1 km), and as with many lunar telescopic photographs, much of the available surface of Mercury is distorted by foreshortening due to viewing geometry, or poorly suited for geological analysis and impact-crater counting for age determinations because of high-Sun illumination conditions. Currently available topographic information is also very limited. Nonetheless, Mercury is a geological laboratory that represents (1) a planet where the presence of a huge iron core may be due to impact stripping of the crust and upper mantle, or alternatively, where formation of a huge core may have resulted in a residual mantle and crust of potentially unusual composition and structure; (2) a planet with an internal chemical and mechanical structure that provides new insights into planetary thermal history and the relative roles of conduction and convection in planetary heat loss; (3) a one-tectonic-plate planet where constraints on major interior processes can be deduced from the geology of the global tectonic system; (4) a planet where volcanic resurfacing may not have played a significant role in planetary history and internally generated volcanic resurfacing may have ceased at ∼3.8 Ga; (5) a planet where impact craters can be used to disentangle the fundamental roles of gravity and mean impactor velocity in determining impact crater morphology and morphometry; (6) an environment where global impact crater counts can test fundamental concepts of the distribution of impactor populations in space and time; (7) an extreme environment in which highly radar-reflective polar deposits, much more extensive than those on the Moon, can be better understood; (8) an extreme environment in which the basic processes of space weathering can be further deduced; and (9) a potential end-member in terrestrial planetary body geological evolution in which the relationships of internal and surface evolution can be clearly assessed from both a tectonic and volcanic point of view. In the half-century since the launch of Sputnik, more than 30 spacecraft have been sent to the Moon, yet only now is a second spacecraft en route to Mercury. The MESSENGER mission will address key questions ...

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Properties of the Hermean Regolith II. Disk-Resolved Multicolor Photometry and Color Variations of the “Unknown” Hemisphere

Cited by 36 publications

References 43 publications

Properties of the Hermean regolith: IV. Photometric parameters of Mercury and the Moon contrasted with Hapke modelling

Properties of the Hermean regolith: IV. Photometric parameters of Mercury and the Moon contrasted with Hapke modelling

Albedo–color distribution on Mercury

The Geology of Mercury: The View Prior to the MESSENGER Mission

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