ISSN:
1573-0794
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract On the basis of inert gas systematics alone, the soilsnow near the surface at the Apollo 16 landing site can be divided into three major groups: Group I (North Ray Crater Soils), Group II (Light Soils), and Group III (Dark Soils). Only five soils do not fit this scheme. The inert gas-based classification is correlated with the chemistry of the soils. Group I soils are relatively poor in K, Fe, Ti and Zn, compared to Group II and III soils. The classification is also correlated with reflectivity. Group I and II soils are generally the light soils in the landing area, while the Group III soils are the dark soils. The groups are not randomly distributed in the landing area. Group I soils occur only at stations 11 and 13 on the ejecta blanket of North Ray Crater. Group II soils occur abundantly at stations 1 and 2, and in spots on Stone Mountain. Group III soils are abundant on Stone Mountain and at station 10. We suggest here that Group I soils are principally derived from the light friable unit, one of the three units inside North Ray Crater, as described by Ulrich. We suggest that Group II soils are mainly derived from the light matrix breccia unit. Group III soils are mixtures of materials from all three units. We conclude that soils with the properties of Group III soils have been at the surface continuously for long times. However, going backwards in time, these soils probably had increasingly larger (Ar40/Ar36)t ratios. The ejecta blanket of North Ray Crater is a temporary ‘anomaly’ in the landing site. However, soils with the properties of Group I soils, but with larger (Ar40/Ar36)t ratios may turn up in Apollo 16 core tubes. The Group II soils show a record of solar wind exposure in the distant past (i.e., they have relatively large Art 40/ARt 36 ratios). From this we conclude that the regolith at Apollo 16 contains sizeable ‘pockets’ or horizons at depth which are the sources of the Group II soils. The materials in these pockets may be akin to soil 61 220.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00567509
Permalink
