As this excellent book demonstrates, the study of comets has now reached the fas cinating stage where we understand comets in general simple tenns while, at the same time, we are uncertain about practically all the details of cometary nature, structure, processes, and origin. In every aspect, even including dynamics, a choice among several or many competing theories is made impossible simply by the lack of detailed knowledge. The space missions, snapshot studies of two comets, partic ularly the one that immortalizes the name of Sir Edmund Halley, have produced a huge mass of valuable new infonnation and a number of surprises. Nonetheless, we face the tantalizing realization that we have obtained only a fleeting glance at two of perhaps a hundred billion (lOll) or more comets with possibly differing natures, origins, and physical histories. To my personal satisfaction, comets seem to have discrete nuclei made up of dirty snowballs, as I concluded four decades ago, but perhaps they are more like frozen rubbish piles.

Klappentext

The space-age view of cometary physics and chemistry is dealt with in this book. Physics and Chemistry of Comets presents in detail our current knowledge of comets based on the scientific data from the spacecraft missions of 1986 to Halley's comet. Nucleus, neutral coma, plasma, dust, and the origin and evolution of comets are treated in eight carefully edited chapters written by leading experts in the field. Advanced students and researchers in space physics, planetology, geophysics and cosmochemistry will find this an authoritative, longstanding reference source.

Inhalt

1. Introduction.- 1.1 Plan of the Book.- 1.2 General Concepts.- 1.3 Orbits of Some Comets for Spacecraft Missions.- 1.4 The Oort Cloud Compared to the Planetary Orbits.- 1.5 Summary of Spacecraft Data from Comets.- 1.6 Summary of New Data from Remote Sensing.- 1.7 Reasons for Planned and Proposed Comet Missions.- 1.8 Laboratory and Space Experiments and Simulations.- 2. The Nucleus.- 2.1 Introduction.- 2.2 Observational Techniques.- 2.3 Models of the Nucleus.- 2.4 The Nucleus of Comet P/Halley.- 2.5 Modeling and Laboratory Experiments.- 2.6 Physical Parameters of the Nucleus.- 2.7 Summary.- 3. The Neutral Coma.- 3.1 Introduction.- 3.2 The Coma: A Transient Phenomenon.- 3.3 Excitation and Emission Mechanisms.- 3.4 Composition of the Coma.- 3.5 Summary and Prospectus.- 4. Dust.- 4.1 Introduction.- 4.2 What is Comet Dust?.- 4.3 Dust Release from the Nucleus.- 4.4 Dust Emission.- 4.5 Dust Coma Structure.- 4.6 Dust Tails.- 4.7 Mass Distribution.- 4.8 Optical and Infrared Properties.- 4.9 Dust Composition.- 4.10 Dust Production Rate and the Dust to Gas Ratio.- 4.11 Summary.- 5. The Plasma.- 5.1 Introduction.- 5.2 Large-Scale Processes of the Solar Wind-Comet Interaction.- 5.3 Ion Composition.- 5.4 Ionospheric Processes.- 5.5 Plasma Wave Turbulence.- 5.6 Ion Acceleration.- 6. Orbital Distribution of Comets.- 6.1 Introduction.- 6.2 Origin and Dynamical Evolution.- 6.3 Time Scales.- 6.4 The Outer Part of the Presolar Nebula.- 6.5 The Distribution of the Reciprocal Semimajor Axes.- 6.6 Other Theories for the Origin and Evolution.- 6.7 Short-Period Comets.- 6.8 Differences Between Long- and Short-Period Comets.- 7. Comet Formation and Evolution.- 7.1 Introduction.- 7.2 Chemical and Physical Clues from Observations.- 7.3 Formation of Comet Nuclei.- 7.4 Dynamical Evolution of Comets.- 7.5 Physical Evolution of Comet Nuclei.- 7.6 Summary.- 8. Implications of Comet Research.- 8.1 Introduction.- 8.2 Progress in Physics and Chemistry of Comets.- 8.3 Progress on the History of the Early Solar System.- 8.4 Comets and the Origins of Life.- 8.5 Unsolved and New Problems.- References.