Saturn's Icy Moon Rhea: a Prediction for Bulk Chemical Composition and Physical Structure at the Time of the Cassini Spacecraft First Flyby

I report a model for the formation of Saturn's family of mid-sized icy moons to coincide with the first flypast of Rhea by the Cassini Orbiter spacecraft on 26 November 2005. It is proposed that these moons had condensed from a concentric family of orbiting gas rings that were cast off some 4600 Myr ago by the contracting proto-Saturnian cloud. Numerical and structural models for Rhea are constructed on the basis of a computed bulk chemical mix of hydrated rock (mass fraction 0.385), H2O ice (0.395), and NH3 ice (0.220). The large proportion of NH3 in the ice mass inhibits the formation of the dense crystalline phase II of H2O ice at the satellite's centre. This may explain the absence of compressional features on the surface. The favoured model of Rhea has a chemically uniform interior and is very cold. The satellite is nearly isodense and the predicted value of the axial moment-of-inertia factor is C/MR^2 = 0.399 +/- 0.004. NH3 is unstable at Saturn's distance from the Sun, except near the polar regions of the satellite. Perhaps the Cassini Orbiter will discover indirect evidence for NH3 through the sublimative escape of this ice from the outer layers, especially near the equatorial zones. Wasting of NH3 would weaken the residual soil, so making the edges of craters soft and prone to landslides. It will be exciting to learn what Cassini discovers.Comment: This paper was submitted to the Publications of the Astronomical Society of Australia (PASA) on 30 November 200

Saturn: Origin and composition of its inner moons and rings

The contraction of the primitive protosaturnian cloud, using ideas of supersonic turbulent convection was modeled. The model suggested that each of Saturn's inner moons, excepting Rhea, condensed above the ice-point of water and consists primarily of hydrous magnesium silicates. The satellite mean densities steadily increase towards the planet and the rocky moons are irregular in shape

Voyager and the origin of the solar system

A unified model for the formation of regular satellite systems and the planetary system is outlined. The basis for this modern Laplacian theory is that there existed a large supersonic turbulent stress arising from overshooting convective motions within the three primitive gaseous clouds which formed Jupiter, Saturn, and the Sun. Calculations show that if each cloud possessed the same fraction of supersonic turbulent energy, equal to about 5% of the cloud's gravitational potential energy, then the broad mass distribution and chemistry of all regular satellite and planetary systems can be simultaneously accounted for. Titan is probably a captured moon of Saturn. Several predictions about observations made by Voyager 2 at Saturn are presented

Neptune's Triton: A moon rich in dry ice and carbon

The encounter of the spacecraft Voyager 2 with Neptune and its large satellite Triton in August 1989 will provide a crucial test of ideas regarding the origin and chemical composition of the outer solar system. In this pre-encounter publication, the possibility is quantified that Titron is a captured moon which, like Pluto and Charon, originally condensed as a major planetesimal within the gas ring that was shed by the contracting protosolar cloud at Neptune's orbit. Ideas of supersonic convective turbulence are used to compute the gas pressure, temperature and rat of catalytic synthesis of CH4, CO2, and C(s) within the protosolar cloud, assuming that all C is initially present as CO. The calculations lead to a unique composition for Triton, Pluto, Charon: each body consists of, by mass, 18 1/2 percent solid CO2 ice, 4 percent graphite, 1/2 percent CH4 ice, 29 percent methanated water ice and 48 percent of anhydrous rock. This mix has a density consistent with that of the Pluto-Charon system and yields a predicted mean density for Triton of 2.20 + or - 0.5 g/cu cm, for satellite radius equal to 1,750 km

Selected bibliography of remote sensing

Bibliography of remote sensing techniques for analysis and assimilation of geographic dat

Copernican Unity versus Ptolemaic Discord

Non-fiction by G.R. Prentice

Stress and Obesity: Facilitation of Neuroendocrine and Autonomic Nervous System Recovery from Stress while Eating Comfort Foods?

Obesity and dysfunctional eating are prevalent and costly concerns in the United States and throughout the world (CDC, 2007; Mathus-Vliegen et al., 2008). Research into the etiology of these conditions points to problems regulating eating, particularly during times of stress. The animal literature suggests that eating during and following stress may lead to a more immediate physiological recovery from stress (e.g., Bulwalkda et al., 2001; Pecoraro et al., 2004). The present study was designed to test this phenomenon in humans; that is, to determine if eating a favorite food immediately after stress would lead to enhanced physiological recovery from stress; and if so, for whom does the phenomenon occur? Fifty two young adults (13 men, 37 women; average age = 19.8 years) completed an entrance survey and then were invited into the laboratory for two separate sessions. Participants engaged in a modified Trier Social Stress Test while physiological (heart rate, blood pressure, heart rate variability, salivary cortisol) and affective (PANAS) measures of reactivity and recovery were gathered. During one of the sessions (Food Session), participants ate a favorite food immediately following stress. A pairedsamples t-test comparing Food and No Food recovery showed a significant difference in recovery for heart rate, t(52) = 3.72, p \u3c .001, and systolic blood pressure, t(48) = 2.9, p \u3c .01 between the Food and No Food sessions; however, it was opposite of the predicted direction. Participants showed a slower heart rate and systolic blood pressure recovery during the Food session compared to the No Food session. Additionally, emotional eating scores were associated with slower systolic blood pressure recovery, beta = .31, t(47) = 2.17, p \u3c .05. These results suggest that food does not improve physiological recovery time following stress, but that eating following stress may increase recovery time, especially for people with dysfunctional eating patterns, leading to poorer long-term health outcomes