Minor bodies in the Solar System, though representing only a small fraction of the mass in the Solar System, may well play a fundamental role in terrestrial evolution. This book contains investigations of the dynamics and physics of comets, asteroids and meteor streams, and the rather controversial topic of periodic phenomena in the Solar System as signified by geological records, together with several associated developments in celestial dynamics. All these problems are interwoven. This book makes a contribution towards unravelling the nature of the interactions between the Earth and its celestial environment.

The last decade of this century has seen a renewed interest in the dynamics and physics of the small bodies of the Solar System, Asteroids, Comets and Meteors. New observational evidences such as the discovery of the Edgeworth-Kuiper belt, refined numerical tools such as the symplectic integrators, analytical tools such as semi-numerical perturbation algorithms and in general a better understanding of the dynamics of Hamiltonian systems, all these factors have converged to make possible and worthwhile the study, over very long time spans, of these "minor" objects. Also the public, the media and even some political assell}blies have become aware that these "minor" objects of our planetary environnement could become deadly weapons. Apparently they did have a role in Earth history and a role more ominous than "predicting" defeat (or victory, why not?) to batches of credulous rulers. Remembering what may have happened to the dinosaurs but keeping all the discretion necessary to avoid creating irrational scares, it may not be unwise or irrelevant to improve our knowledge of the physics and dynamics of these objects and to study in particular their interactions with our planet.

Planet Earth is part of our Galactic environment, not just the product of it, and it is still today influenced by phenomena related to Galactic forces. Specifically, our planet is affected by its near environment, in particular the small bodies in the Solar System. This book reviews the processes which cause the collisions of these small bodies with the Earth as well as the consequences of such collisions. The various articles take the reader through the Galaxy-Solar System connection to the orbital dynamics of the small bodies and to their number and distribution in near-Earth space. The hazards of the impacts of small bodies on Earth are evaluated, and the geophysical records of such impacts are discussed. The book takes the reader to the forefront of research on both impact cratering and the origin and evolution of small bodies in the Solar System. Thus it brings together two subjects, geophysics and astronomy, which are usually discussed in separate volumes but are closely knit together in this particular area of research.

The exploration of our Solar System is rapidly growing in importance as a scientific discipline. During the last decades, great progress has been achieved as the result of space missions to planets and small bodies - as teroids and comets - and improved remote-sensing methods, as well as due to refined techniques of laboratory measurements and a rapid progress in theoretical studies, involving the development of various astrophysical and geophysical models. These models are based, in particular, on the approach of comparative planetology becoming a powerful tool in revealing evolu tionary processes which have been shaping the planets since their origin. Comets and asteroids, being identified as remnants of planetary formation, serve as a clue to the reconstruction of Solar System history because they encapsulated the primordial material from which the planets were built up. At the same time, these interplanetary carriers of original matter and mes sengers from the past, being triggered by dynamical processes well outside our neighboring space, were responsible for numerous catastrophic events when impacting on the planets and thus causing dramatic changes of their natural conditions. In the crossroads of astronomy and geophysics, recent years have seen a growing understanding of the importance of collisional processes through out the history of the Solar System and, therefore, the necessity to get more insight into the problem of interactions of planets and small bodies.

IAU Transactions are published as a volume corresponding to each General Assembly. Volume A is produced prior to the Assembly and contains Reports on Astronomy, prepared by each Commission President. The intention is to summarize the astronomical results that have affected the work of the Commission since the production of the previous Reports up to a time which is about one year prior to the General Assembly. Volume B is produced after the Assembly and contains accounts of Commission Meetings which were held, together with other material. The reports included in the present volume range from outline summaries to lengthy compilations and references. Most reports are in English.

For the late great Mike Davis, the ravaging of the climate by capital—and his prescient analysis of its consequences for those of us left to deal with the resulting crises—was always a central part of his urban geography. In these wide ranging, incisive, and hauntingly relevant essays, Davis asks us to consider what we would find if we put a microscope to the ruins of Metropolis, and provides a riveting account of the disasters—natural, man-made, and those (as in the case of climate calamity) where the distinction is impossible to make—that he finds on the other end. He begins his examination by sifting through the rubble of the twin towers in the wake of 9/11, presciently identifying the seeds of war already germinating in the scorched soil of ground zero, and closes by considering how little prepared our hollowed out urban infrastructure is to deal with shocks of any kind, be they from car bombs or ice storms. In between we are treated to tours of blasted wastelands where American generals built and destroyed replicas of Berlin, glimpses of Las Vegas’s penchant for annihilating its own best-known landmarks, and other riveting tales of the dialectic between nature and the city. Dead Cities, written over twenty years ago, abounds with prophecies fulfilled, contains echoes of our current moment where conspiracies abound and anxieties drown out official celebrations of prosperity, and offers dreams of alternative paths not taken.