Pat WILDE Marine Sciences Group, Department of Paleontology, University of California, Berkeley, CA 94720) (Sponsor. M. S. Quinby-Hunt)
In his classic paper on the origin of seawater Rubey (1951) noted the improbability of deriving water, chlorine, sulfur, and bromide in sea water as the product of weathering igneous rocks. This geochemical inbalance was reinforced by the recalculations of Horn and Adams (1966). Rubey's explanation that the source of the volatile elements was outgassing from volcanoes has remained the accepted explanation to date (Holland, 1984). However, the discovery of Ice and Sulfur satellites of Jupiter, Saturn, and Uranus suggest the possibility of ice and other volatile planetesmals characteristic of the Gas Giant planets being present during the formation of the Earth and the Solar System. For example, the volume of the Earth's ocean (1.3x109 km3) is between the equivalent water volume of the Saturian satellite Rhea (1x109 km3) and Iapetus (1.6x109 km3).
Comparable ice-volatile planetesmals may be the original source of the oceans. Such a primordial ocean would only develop in the late stages of accretion after the Earth reached sufficient sin to have a gravity high enough to prevent escape of volatiles through the atmosphere and cool enough to support liquid water. Subsequent differentiation and outgassing of stony planetesmals combined with cycling of the volatiles through oceanic ridges and erosion of the continents resulted in the additional 'salt" content of the present oceans whose elements are in geochemical balance. The relative constancy of oceanic salinity in the last 600 million years may be a relict of the mean content of the impacting ice planetesmals as 60% by weight of the salinity is CI- and S042-.
The Dittmarian conservancy of the Rubey volatiles may be the result of the initial composition of the ice-volatile planetesmals modified by reactions with stony planetesmals over Geologic time. The volume of the oceans would grow or decline from the initial volume as a function of the ratio of the amount of volatiles escaping into space to the amount outgassing from the crust and mantle.
Primordial oceans may have developed in a similar manner on both Venus and Mars. The Cytherean Ocean probably was volatilized by the heat, while the Martian Ocean eventually evaporated due to the low gravity. The fluvial features on Mars may be the last relicts of ocean-regulated hydrological cycle
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SATELLITE STATISTICS FOR MOONS WITH DENSITY ESTIMATIONS**
Satellite Name Diameter (Km) Density Distance from planet (Thousand Km) Orbital period (Earth Days) Eccentricity of Orbit Inclination of orbit to parent planet's equatorial plane Earth Moon 3476 3.34 384.4 27.322 0.05 5.145º Mars Phobos 28 x 20 2.0 9.38 0.319 0.01 1.0º Deimos 16 x 12 1.7 23.46 1.263 0.00 0.9º Jupiter Io 3629 3.57 421.3 1.769 0.00 0.04º Europa 3136 2.97 670.5 3.551 0.01 0.47º Ganymede 5258 1.94 1069.3 7.155 0.00 0.19º Callisto 4796 1.86 1881 16689 0.01 0.288º Saturn Mimas 389 1.17 185.4 0.942 0.02 1.53º Enceladus 500 1.24 237.8 1.370 0.00 0.02º Tethys 1049 1.26 294.4 1.888 0.00 1.09º Dione 1120 1.44 377.1 2.737 0.00 0.02º Rhea 1529 1.33 526.1 4.518 0.00 0.35º Titan 5150 1.88 1221.1 15.945 0.03 0.33º Iapetus 1438 1.21 3559 79331 0.03 14.72 Uranus Miranda 470 1.35 129.70 1.414 0.00 3.40º Ariel 1158 1.66 191.1 2.520 0.00 0.00º Umbriel 1168 1.51 264.2 4.144 0.00 0.00º Titania 1578 1.68 435.6 8.706 0.00 0.00º Oberon 1519 1.58 582.3 13.463 0.00 0.00º Neptune Triton 2700 2.07 354.6 5.877 0.00 157º Pluto Charon 1189 2 19.6 6.387 0.00 98.8º
**This Table modified from email@example.com. Material Copyright © 2000 Pete