Surfaces Of Atmosphereless Bodies Research Articles

Determining the size of craters on the surfaces of atmosphereless bodies in Solar system with ground-based methods

Determining the size of craters on the surfaces of atmosphereless bodies in Solar system with ground-based methods

Water detection on atmosphereless celestial bodies: Alternative explanations of the observations

Alternative explanations are proposed for the results of the three types of remote sensing experiments in which water ice is supposed to be found on the surfaces of atmosphereless celestial bodies: (1) measurements of hydrogen content by the neutron spectrometer on Lunar Prospector, (2) observations of the absorption bands near 3 μm in reflectance spectra of asteroids, and (3) radar observations of polar regions of Mercury. Calculations have shown that in the first two types of observations solar wind protons chemically trapped by oxygen atoms in hydroxyl groups or other radiation defects in oxygen‐bearing particles on the surfaces of atmosphereless bodies can be mistaken for water. Higher hydrogen content in the lunar polar regions, especially in polar craters, as compared to equatorial zones can be due to sharp decrease of escape probability with temperature. Spots of high hydrogen content in equatorial zones of the Moon can be explained by variations of degassing rates in different materials. Solar wind origin of OH groups may account for 3‐μm absorption by asteroids of M and E classes thought to be differentiated. Strong, highly depolarized radar echoes from polar and lower latitude craters of Mercury can be explained by decrease of the dielectric loss of silicate material with temperature, which solves the problems of delivery and thermal stability of low‐loss material on Mercury surface, being consistent with the observed regional variations of radar brightness. The possibilities considered in the paper should be taken into account in interpretation of the observations aimed on search of water.

Radiative transfer in the surfaces of atmosphereless bodies. III - Interpretation of lunar photometry

view Abstract Citations (19) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radiative transfer in the surfaces of atmosphereless bodies. III. Interpretation of lunar photometry. Lumme, K. ; Irvine, W. M. Abstract Narrowband and UBV photoelectric phase curves of the entire lunar disk and surface photometry of some craters have been interpreted using a newly developed generalized radiative transfer theory for planetary regoliths. The data are well fitted by the theory, yielding information on both macroscopic and microscopic lunar properties. Derived values for the integrated disk geometric albedo are considerably higher than quoted previously, because of the present inclusion of an accurately determined opposition effect. The mean surface roughness, defined as the ratio of the height to the radius of a typical irregularity, is found to be 0.9 + or - 0.1, or somewhat less than the mean value of 1.2 obtained for the asteroids. From the phase curves, wavelength-dependent values of the single scattering albedo and the Henyey-Greenstein asymmetry factor for the average surface particle are derived. Publication: The Astronomical Journal Pub Date: July 1982 DOI: 10.1086/113192 Bibcode: 1982AJ.....87.1076L Keywords: Astronomical Photometry; Lunar Craters; Lunar Surface; Radiative Transfer; Asteroids; Electrophotometry; Light Scattering; Lunar Albedo; Natural Satellites; Phase Shift; Regolith; Surface Properties; Surface Roughness; Ubv Spectra; Lunar and Planetary Exploration; Albedo:Moon; Moon:UBV Photometry; Moon Surface:Radiative Transfer full text sources ADS |

Radiative transfer in the surfaces of atmosphereless bodies. I - Theory. II - Interpretation of phase curves

A generalized theory of radiative transfer is presented which includes single and multiple scattering of light in particulate surfaces, and is applicable to both the surfaces of atmosphereless bodies and to laboratory samples. Single scattering is described in terms of the effects of porosity and roughness, and is formulated by means of a probabilistic method. It is shown that, for low-albedo surfaces, the effects of porosity and roughness are separable, the opposition effect is caused by the former, and the slope of the linear part of the phase curve is mainly controlled by the latter. The theory, which is applicable to all albedos and phase angles, may be used in both surface brightness and integrated brightness studies. The limiting case of roughness and volume density tending to zero yields the results of classical radiative transfer theory.

Radiative transfer in the surfaces of atmosphereless bodies. II. Interpretation

Radiative transfer in the surfaces of atmosphereless bodies. II. Interpretation