Jupiter s satellites

Prieto-Ballesteros O, Kargel JS (2005) Thermal state and complex geology of a heterogeneous salty crust of Jupiter s satellite, Europa. Icarus 173 212-221... 

Sulfur (S) is second only to carbon in the number of known allotropes formed. The existence of at least twenty-two sulfur allotropes has been demonstrated. The simplest allotrope of sulfur is the violet disulfur molecule, S2, analogous to the dioxygen molecule. Unlike O2, however, S2 does not occur naturally at room temperature and pressure. It is commonly generated in the vapor generated from sulfur at temperatures above 700°C. It has been detected by the Hubble Space Telescope in volcanic eruptions on Jupiter s satellite, lo. 

Ole Rcemer (1644—1710), the Danish astronomer famous for his measurement of the velocity of light from a study of the movements of Jupiter s satellites, used a mixture of ice and common salt or a similar one (ice and sal ammoniac) in obtaining his zero, which was regarded as the lowest temperature then attainable in the laboratory. This mixture was not entirely satisfactory and Fahrenheit later pointed out that a different result might be obtained in summer from that in winter (p. 226). 

Photometric and polarimetric data obtained from telescopic observations and laboratory measurements at small phase angles have been accnmnlating for many years however, the interpretation of these effects, especially of the polarization branch, was not satisfactory until recently [7-20] when the coherent backscattering (interference) mechanism was developed to explain both effects. Since that time, additional experimental [21-23] and theoretical [18, 24-28] data were obtained, showing that the effects are more complex than initially considered. For example, negative polarization branches with two minima were discovered for some Jupiter satellites and bright asteroids [29,30], and unusual behavior of the opposition spike amphtude with albedo for the Moon, asteroids, and Jupiter s satellite Europa were found [31-33]. 

Kargel JS, Consolmagno GJ (1996) Magnetic fields and the detectability of brine oceans in Jupiter s icy satellites. Lunar Planet Sci 27 643-644... 

Fig. 1. A schematic diagram of the orbital positions of the moons of Jupiter discovered by Galileo. Their positions are scaled to Jupiter s radius (Rj) with properties given in Table 1. Note these satellites, like our moon, are all phase locked to the parent planet, hence the same side faces Jupiter throughout each moon s orbit. Since the magnetic field is attached to Jupiter, it rotates faster, therefore, in addition to ions and electrons moving up and down the field lines and impacting the satellites, there is a net preferential flow onto the hemisphere trailing the satellite s motion.

Sulfur and sulfur compounds and their relationship to volcanic silicate rocks are at the heart of lo s surface chemistry. The satellite s low ultraviolet albedo combined with high visible and near-infrared reflectance suggested elemental sulfur to a number of researchers studying telescopic spectra (Wamsteker, 1973 Wamsteker et al., 1974), although laboratory measurements of pure sulfur differ somewhat from lo s average color. The presence of sulfur ions detected in Jupiter s magnetosphere near lo (Kupo et al., 1976) also pointed toward an lo source of sulfur. 

Saturn s retinue of satellites is qualitatively quite different from Jupiter s fellow travelers. The system contains just one large satellite, Titan, which is virtually identical in bulk properties to Ganymede and Callisto. Titan s density, determined from Voyager observations, suggests a ice/rock composition and a probable differentiated interior by analogy with the Jupiter satellites. Titan s atmosphere, the first discovered for a planetary satellite, was detected in 1944 through identification of methane gas absorptions in its spectrum (Kuiper, 1944). 

Although less intense than Jupiter s environment, the Saturn magnetosphere contains both low-energy plasma and high-energy radiation that interacts with the satellite surfaces. It is likely that oxygen and hydroxyl ions in the magnetosphere result from material sputtered from the... 

Pollack J. B. and Reynolds R. T. (1974) Implications of Jupiter s early contraction history for composition of Galilean satellites. Icarus 21, 248-253. 

An example where both mechanisms operate is Calfisto, Jupiter s outermost Galilean satellite, which is both heavily cratered and distinguished by a variegated... 

In Fig. 4.4 a comparison of the reflectivity of Amalthea, Thebe, Callisto and Asteroids is given (obtained with the 8.2 m Subaru Telescope). Thebe is a small satellite of Jupiter (55 x 45 km), Amalthea is one of the inner satellites of Jupiter (mean diameter about 165 km). In this figure the signature of water is clearly seen. Amalthea radiates more energy than receiving, maybe it is heated by electric currents in Jupiter s magnetosphere. 

Water can be found, in all three aggregate states, almost everywhere in the universe as ice in the liquid phase on the satellites of the outer solar system, including Saturn s rings and in the gaseous state in the atmospheres of Venus, Mars and Jupiter and in comets (as can be shown, for example, from the IR spectra of Halley s comet). The OH radical has been known for many years as the photodissociation product of water. 

Evaporites on Mars and Europa. The NASA s robotic explorers, Spirit and Opportunity, landed on at Mars and examined their landing sites for past environmental conditions. Kinds of minerals in a hot-spring environment and dried-up lake beds were photographed suggesting future use of ESR to date these evaporate with a portable ESR on the rover. Sulfate mineral precipitation, epsonite, MgS04 with 7 hydration water molecules in frozen ice, was studied by sampling the icy environment, especially icy fault on the surface of Europa, a satellite of Jupiter.61... 

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