Search NASA⌕ Search

Engineering topics

Ringwood, A. E.

Publications and source records attributed to Ringwood, A. E..

12 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Nickel-cobalt systematics and their bearing on lunar origin

The earliest metal phases to crystallize from the least-fabricated low Ti mare basalts contain about 30% Ni and 2 to 7% of Co. Experimental investigations of partitioning of Ni and Co between primitive lunar basaltic magmas and metal phases are currently in progress. Preliminary results show that the metal phase crystallizing near the liquidus of Green Glass (185 ppm Ni, 70 ppm Co) would contain about 40% Ni and 2.3% Co. It seems, therefore, that if a lunar core does exist, as suggested by the results of (2), it is relatively rich in Ni (30-40%) and Co (2-7%). This composition presents a remarkable contrast to that of the Earth's core which is estimated to contain about 6% Ni and 0.3% Co. Explanations for the differing densities of Earth and Moon are imvestigated.

Ringwood, A. E.↗
NASA NTRS1984

Origin of the Moon

The similarities in siderophile abundances strongly suggest that the Moon was derived from the Earth's mantle after the Earth's core had formed. The energy required to remove material from the Earth's mantle and place it into geocentric orbit can be supplied most readily by impact processes during accretion of the Earth. Impacts of late-accreting, high-velocity planetismals would evaporate many times their masses of mantle material. These gases would be accompanied by a massive spray of shock-melted silicate droplets. It is suggested that the gases produced from such near-equatorial impacts were rapidly spun out into equatorial geocentric orbit. The evaporated material was selectively recondensed, and, accompanied by the shock melted, devolatilized silicate droplets, accreted to form a sediment ring of Earth-orbiting planetismals. This sediment ring also captured a significant proportion of Earth-bound planetismals. The Moon was formed by accretion from planetismals comprising the sediment ring.

Ringwood, A. E.↗
NASA NTRS1977

Earth and Venus - A comparative study

Two hypotheses attempting to account for the anomalously low intrinsic density of Venus in terms of chemical fractionation processes are entertained. Both assume similar relative abundances of major elements (Fe, Si, Mg, Al, Ca) in Venus and earth. One model assigns a larger proportion of the total Fe present in Venus to the planetary mantle, implying a core/mantle ratio lower than that of earth, and more extensive oxidation. The alternate hypothesis projects a Venus more reduced than the earth, with a mantle devoid of oxidized Fe; the difference in intrinsic densities is then attributed to the earth accreting at a lower temperature consonant with its greater distance from the sun. Large amounts of sulfur are presumed accreted on the earth but not on Venus, in the second model. Available chemical evidence tends to favor the first model.

Ringwood, A. E.↗
NASA NTRS1976

Mare basalt petrogenesis in a dynamic moon

An hypothesis for mare basalt petrogenesis is presented. In the proposed model, both high- and low-Ti mare basalts are produced by partial melting and hybridization at depth accompanied by equilibrium between the hybrid liquids and the local olivine-pyroxenite residuum. The energy source for mare basalt formation is ultimately provided by radiogenic heating in the primordial lunar interior. The proposed dynamic model explains similarities in the Mg/(Mg+Fe) ratios and Cr2O3 contents of high-Ti and low-Ti basalts and avoids thermal problems inherent in previous models.

Kesson, S. E.↗