Ring Composition And Particle Properties

Ring composition The composition of the rings is one of their oldest puzzles, and perhaps the most important for establishing their origin (Section 10.7). It has long been known that water ice is abundant in the rings, from near-infrared spectra and microwave observations (Chapter 9). Cassini's VIMS instrument measures spectra at wavelengths from visible through 5 micrometers in the near-infrared it is at these near-infrared wavelengths where the strongest absorptions due to water ice are...

The Voyager Neptune Encounter

Voyager 2 was going to be the first spacecraft from Earth to visit Neptune. However, a Voyager 2 Neptune encounter was not always in the approved plan or in the budget. Fortunately, mission planners continued to keep the possibility alive from the mission's very inception back in the early 1970s. Almost 20 years later very little had changed to increase our understanding of the planet. Voyager 2 was going to pass Table 5.1. Neptune stellar occultations observed from 1968 to 1989 8 . Table 5.1....

Main Ring Structure

Cassini Soi Ring

Radial structure As mentioned above, one of the major uncertainties about Saturn's main rings has been Just how much material do the thickest parts contain For example, during Voyager, the tilt angle of the rings was only a few degrees as seen from Earth and the Sun, so neither sunlight nor Voyager's radio transmission could penetrate the densest regions, and the single observation of a star shining through the rings was limited by noise 15 , so we have remained largely ignorant of its...

Gravitational Interactions Of Saturns Rings And Satellites

Saturn has more regular satellites than any other planet in the solar system. Although some of these regular satellites (i.e., satellites with prograde, low-inclination, low-eccentricity orbits) may not be high-density, well-consolidated objects most of them interact gravitationally with Saturn's ring system. The regular satellites include the classical satellites Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion, and Iapetus. Prior to any new discoveries by Cassini, the set of regular...

Galileo Ring Observations

During Galileo's many years of operations, its science instruments revealed many additional details about the three distinct parts of the planet's ring system. The inner donut-shaped ring, called the Halo ring, may extend all the way to the planet's cloud tops. Outside of the Halo ring is an optically thicker and flatter ring, known as the Main ring. The third and most distant part of the system is the tenuous Gossamer ring. The Gossamer ring in actuality is composed of two overlapping rings....

Interactions Between Saturns Rings And Magnetic Field

Gravitational forces by seen and unseen satellites and by Saturn itself probably generate the majority of Saturn's ring features. Saturn's gravity, with the help of meteoroids from outside the Saturn system and mutual collisions between the ring particles themselves, is responsible for the breakup of larger bodies that approach within the Roche limit (see Chapter 1). The oblateness (polar flattening) of the planet also keeps the rings and the satellites which interact gravitationally with the...

Ringparticle Properties

The beginning of our understanding of the sizes of the ring particles came as a result of the discovery in 1973 that Saturn's rings are strong radar reflectors 36 . Unless the ring particles were at least as large as the radar wavelength (12.6 cm), there would have been no reflected radar signal detected. The rings were expected to be transparent to radar on the basis of failure to observe any passive radio signals from Saturn's rings prior to that date. The transmitted radar signal was...

List of figures

1.1 Five views of Saturn from the Hubble Space 1.2 Brigham Young University's Eyring Science Center and telescope 3 1.3 Jupiter's Main and Halo 1.4 Neptune's Le Verrier and Adams rings, with ring arcs in the latter 6 1.5 Spiral density and bending waves in Saturn's A 1.6 The solar system's Oort Comet 2.1 Detailed drawings of the Moon made by Galileo in 2.2 Galileo's sketch of Saturn and its two companions in 1610 18 2.3 Galileo's sketch of Saturn with cup handles in 2.4 Thirteen views of Saturn...

Notes And References

1 Morrison, D., Samz, J., Voyage to Jupiter, NASA SP-439, 1980, p. 84. 2 Personal communication with Tobias Owen. 3 Elliot, J., Kerr, R., 1984, Rings Discoveries from Galileo to Voyager, The Massachusetts Institute of Technology Press, 1984, p. 100. 5 Personnel communication with Candice Hansen-Koharcheck. 6 Morrison, D., Samz, J., (1980) Voyage to Jupiter, NASA SP-439, p 85. 9 Personnel communication with Charles C. Avis. 10 Caption found at 11 Flight Science Office Science and Mission...

The Rings Of Neptune

Data from Voyager 2's encounter revealed that Neptune has five continuous rings. Starting from the innermost ring and working outward, they are now named Galle, Le Verrier, Lassel, Arago, and Adams (Figure 5.2). Each is named after a prominent 19th-century astronomer who had a major role leading to uncovering the true nature of this trans-Uranian planet. The rings do not all have the same structure. Le Verrier, Arago, and Adams are very narrow and distinct while Galle and Lassell are broad and...

Ringmoons And Ringlets

As discussed in Chapter 9 and Section 10.3, moonlets are intimately intermingled in all planetary ring-moon systems. Those orbiting within and just outside Saturn's main rings are responsible for exciting a large number of spiral density waves, such as those in Figures 10.6 and 10.7, which may be used to determine their mass. Since we now have very good images of these moons giving their volume, we can easily determine their density. All the close-in ringmoons of Saturn have a density about...

Nomenclature And Radial Dimensions Of The Saturnian Rings

In Chapter 2, the discovery of Saturn's rings was discussed in detail. A general qualitative description of the rings was included with that discussion, as was the nomenclature of the individual ring regions. In Table 9.1, adapted from Cuzzi et al. 1 , the orbital characteristics and estimated masses of the rings are given. For comparison, we also include the inner eight satellites of Saturn known prior to Cassini. The narrow F ring was first discovered by Pioneer 11 during its encounter with...

The Nature Of The Rings

The ring's thickness was not the only erroneous conclusion Huygens had made about the ring Huygens had also proposed that the ring was a solid body 12 . First, astronomers had difficulties explaining the stability and periodic motions of a solid spinning ring. Remember that astronomers of the day did not yet understand the law of gravitation or the laws of planetary motions. Newton's Principia Mathematica, which contained the first formulation of the law of gravitation, would not be published...

Summary And Major Unanswered Questions Before Cassini

The purpose of this chapter has been to set the stage for the spectacular data on Saturn's rings returned by the Cassini Orbiter. In Chapter 10 we report on some of the preliminary findings of this important international space mission. Hopefully, the data we include in this book will whet the appetites of interested readers sufficiently to cause them to search for the later results that will already have appeared or will shortly appear that further expand on our understanding of the Saturn...

First Observations Of Saturns Companions

Galileo Galilei Saturn

The invention of the telescope ended the age of naked-eye astronomy. Astronomers no longer needed to scan the heavens with their eyes alone. The looking glass opened the solar system and indeed the universe to the scrutiny of humanity. The first recorded use of the telescope for astronomical study was performed in 1610 by Galileo Galilei. Using just a 20-powered spyglass, Galileo discovered spots on the Sun, four satellites about Jupiter, and surface features on the Moon see Figure 2.1 . His...

Ring Dimensions

With the exception of the only known blue-tinted rings Saturn's E ring and Uranus's recently discovered 2003U1R ring, both of which appear to be composed of water-ice particles derived from satellites Enceladus and Mab, respectively , all of the known planetary rings are found within 3.2 planetary radii of the centers of their respective planets Figure 11.1 . Well exterior to these rings whose radial positions and dimensions are catalogued in Table 11.1, Uranus and Neptune have dust disks...

List of abbreviations and acronyms

Galileo Millennium Mission Extension InfraRed Interferometer Spectrometer and radiometer International Space Station Imaging Science Subsystem NASA's Gerard P. Kuiper Airborne Observatory Maneuverless Image Motion Compensation National Aeronautics and Space Agency National Radio Astronomy Observatory Visible and Infrared Mapping Spectrometer

Major Differences Between The Known Ring Systems

While the similarities between the ring systems are primarily those that provide a description of planetary ring systems in general, it is the differences that give each ring system its own unique personality and appearance. It is also these individually unique personalities that provide the motivation for this book. Without that diversity, a treatise on planetary ring systems might require little more than a 15-page illustrated magazine article. In this introductory chapter, only a few of the...

Earthbased Observations Of Saturns Rings Since

There are three primary types of observations of Saturn's rings that have provided additional information on the ring system since the Voyager encounters in 1980 and 1981. These include an occultation of the star 28 Sagittarii by Saturn and its rings in 1989, observations at the time of the ring plane crossings of the Earth and the Sun in 1995 and 1996, and radar observations of the rings from the Arecibo Observatory in Puerto Rico from 1999 onward. In addition, there was an extended series of...

Model For The Ring Emerges

In 1642 astronomers began once again to take interest in the problem of Saturn's companions and their slowly changing shape. Notable astronomers like Pierre Gassendi 1592-1655 , Francesco Fontana 1585-1656 , Antonius Maria Schyrlaeus de Rheita 1597-1660 and Johannes Hevelius 1611-1687 all began to make systematic observations of the planet 8 . Although the accumulation of a greater number of observations was necessary for determining the true nature of Saturn and its companions, many of the...

Smaismrmilmepoetaleumibunenugttauiras

Italian astronomer Galileo announced with this anagram sent to his patron astronomer Johannes Kepler on July 30, 1610, that unscrambling his anagram , ALTIS-SIMUM PLANETAM TERGEMINUM OBSERVAVI. Roughly interpreted out of the Latin, Galileo was telling his colleague, I have observed that the most distant of planets has a triple form. Note that U and V are interchangeable in Latin. Of course, Kepler did not understand what Galileo was announcing until Galileo himself later unscrambled the...

Ring Dimensions Shapes And Inclinations

Table 7.1 provides an overview of the mean radial distances, velocities, periods, and masses of the 13 known rings and the 14 inner satellites of Uranus 1 . Their widths, orbital eccentricities and inclinations, and equivalent depths are given in Table 7.2 2 . Because the eccentric rings have widths that vary with orbital longitude, the concept of equivalent depth physical width multiplied by optical depth is important because it remains essentially constant around the ring and is a measure of...