Analysis of planetary evolution with emphasis on differentiation and dynamics

In order to address the early stages of nebula evolution, a three-dimensional collapse code which includes not only hydrodynamics and radiative transfer, but also the effects of ionization and, possibly, magnetic fields is being addressed. As part of the examination of solar system evolution, an N-body code was developed which describes the latter stages of planet formation from the accretion of planetesimals. To test the code for accuracy and run-time efficiency, and to develop a stronger theoretical foundation, problems were studied in orbital dynamics. A regional analysis of the correlation in the gravity and topography fields of Venus was performed in order to determine the small and intermediate scale subsurface structure

Tests of random density models of terrestrial planets

Random density models are analyzed to determine the low degree harmonics of the gravity field of a planet, and therefrom two properties: an axiality P_l , the percent of the degree variance in the zonal term referred to an axis through the maximum for degree l; and an angularity E_(ln) , the angle between the maxima for two degrees l, n. The random density distributions give solutions reasonably consistent with the axialities and angularities for the low degrees, l < 5, of Earth, Venus, and Moon, but not for Mars, which has improbably large axialities and small angularities. Hence the random density model is an unreliable predictor for the non‐hydrostatic second‐degree gravity of Mars, and thus for the moment‐of‐inertia, which is more plausibly close to 0.365MR^2

The Tectonics and Evolution of Venus

This shift corresponded to a focusing of research on Venus. Some work included comparison with other planets. Venus research is being continued. The research can be summarized under five headings: (1) Planet formation; (2) Thermal and Compositional Evolution; (3) Tectonic structures and processes; (4) Determination and interpretation of gravity; and (5) Analyses of Ishtar Terra. Thirty-four publications were produced. References to publications supporting the summary are by year and letter: e.g., (1990 c,d) for the emphasis on the terminal phases in formation studies

1985 Hess Medal to Gerald J. Wasserburg

This is the first presentation of the Harry Hess Medal. Harry Hess was long Professor of Geology at Princeton. He is most renowned as a founding father of seafloor spreading but contributed significantly to a variety of advances in geology and petrology. Harry Hess died in 1969 after seeing man land on the moon, an event of interest to him as chair of the Space Science Board

Response

Singer's comments appear to misinterpret, or miss the emphasis of, several points in our article. 1) He infers that we advocate “raising energy taxes or … directly enforcing conservation.” There are no explicit statements thereof in our article. The main thrust of the criticized item was that the public should be more aware and have a greater spirit of cooperation. We do feel that it is desirable that the public be better informed—something to which the AGU can contribute—entirely aside from governmental compulsion, something which is not AGU's business

AGU Planet Earth Committee Report: Part II: Interior and Crust

The Earth's mantle, core, and crust comprise 99.98% of its mass. The mantle, making up the bulk of the mass at 70% and composed of higher density rocks (rich in magnesium silicates, plus some iron silicates), extends an average of 15–2900 km deep. The core is the center of the Earth, 2900–6370 km deep, composed mainly of molten iron. The crust is the outermost layer of the solid Earth, composed of lower density rocks (rich in silica and aluminum and calcium silicates) 6–40 km thick

Report of the panel on geopotential fields: Gravity field, section 8

The objective of the Geopotential Panel was to develop a program of data acquisition and model development for the Earth's gravity and magnetic fields that meet the basic science requirements of the solid Earth and ocean studies. Presented here are the requirements for gravity information and models through the end of the century, the present status of our knowledge, data acquisition techniques, and an outline of a program to meet the requirements