Abstract From ancient times through to the Renaissance reports of stones, fragments of iron and ‘six hundred other things’ fallen from the sky were written down in books. With few exceptions, these were taken as signals of heaven's wrath. The 18th century Enlightenment brought an entirely new approach in which savants sought rational explanations, based on the laws of physics, for unfamiliar phenomena. They accepted Isaac Newton's dictum of 1718 that outer space must be empty in order to perpetuate the laws of gravitation, and, at the same time, they rejected an old belief that stones can coalesce within the atmosphere. Logically, then, nothing could fall from the skies, except ejecta from volcanoes or objects picked up by hurricanes. They dismissed reports of fallen stones or irons as tales told by superstitious country folk, and ascribed stones with black crusts to bolts of lightning on pyritiferous rocks. The decade between 1794 and 1804 witnessed a dramatic advance from rejection to acceptance of meteorites. The three main contributing factors were E.F.F. Chladni's book of 1794, in which he argued for the actuality of falls and linked them with fireballs; the occurrence of four witnessed and widely publicized falls of stones between 1794 and 1798; and chemical and mineralogicai analyses of stones and irons, published in 1802 by Edward C. Howard and Jacques-Louis de Bournon. They showed that stones with identical textures and compositions, very different from those of common rocks, have fallen at different times in widely separated parts of the world. They also showed that erratic masses of metallic iron and small grains of iron in the stones both contain nickel, so they must share a common origin. Meanwhile, in 1789, Anton-Laurent de Lavoisier had revived the idea of the accretion of stones within the atmosphere, which became widely accepted. Its chief rival was a hypothesis that fallen stones were erupted by volcanoes on the Moon. During the first half of the 19th century falls of carbonaceous chondrites and achondrites, and observations on the metallography of irons, provided fresh insights on the range of compositions of meteorite parent bodies. By 1860 both of the two main hypotheses of origins were abandoned, and debates intensified on whether all meteorites were fragments of asteroids or some of them originated in interstellar space. This paper will trace some of the successes and some of the failures that marked the efforts to gain a better understanding of meteorite falls from the end of the 15th century to the early 20th century.

Abstract In this brief epilogue we take a look into the future and some very topical additional discussion is provided by Ursula Marvin on meteorites and Mars, the topic of Monica Grady’s article (Grady 2006 ). John Wood in a brief but elegant essay has emphasized the failure so far to establish the origin of chondrules, a fundamental — perhaps the most fundamental — question facing meteoriticists at the present time. The alternative impact hypothesis to the nebular was not described in any detail in the chapter on ‘Chondrules and calcium-aluminium inclusions (CAIs)’ (McCall 2006 ) because, at the time of writing, it seemed rather outdated, but it has lately come to prominence again, being favoured by Sears (see Scott 2005 ). As time progresses we hope to see an improved understanding of nebular processes resulting from a closer matching of astrophysical models to data arising from research, such as that conducted on understanding the nature of shortlived isotopes. High-resolution chronologies of events in the early solar system should become more clearly defined. The timescales of accretion and differentiation in the early solar system will then, hopefully, be better understood. This, in turn, can aid in the interpretation of observational data, using more sensitive detector technologies, concerning the evolution of circumstellar discs and stellar formation processes. Exoplanet searches are becoming more sophisticated and the observed range of planetary systems around other stars raises all sorts of interesting questions about planetary dynamics and evolutionary processes. Is our solar system unique or part of a continuum of planetary configurations that

Abstract Since the opening of the Space Age, images from spacecraft have enabled us to map the surfaces of all the rocky planets and satellites in the Solar System, thus transforming them from astronomical to geological objects. This progression of geology from being a strictly Earth-centred science to one that is planetary-wide has provided us with a wealth of information on the evolutionary histories of other bodies and has supplied valuable new insights on the Earth itself. We have learned, for example, that the Earth–Moon system most likely formed as a result of a collision in space between the protoearth and a large impactor, and that the Moon subsequently accreted largely from debris of Earth's mantle. The airless, waterless Moon still preserves a record of the impact events that have scarred its surface from the time its crust first formed. The much larger, volcanic Earth underwent a similar bombardment but most of the evidence was lost during the earliest 550 million years or so that elapsed before its first surviving systems of crustal rocks formed. Therefore, we decipher Earth's earliest history by investigating the record on the Moon. Lunar samples collected by the Apollo astronauts of the USA and the robotic Luna missions of the former USSR linked the Earth and Moon by their oxygen isotopic compositions and enabled us to construct a timescale of lunar events keyed to dated samples. They also permitted us to identify certain meteorites as fragments of the lunar crust that were projected to the Earth by impacts on the Moon. Similarly, analyses of the Martian surface soils and atmosphere by the Viking and Pathfinder missions led to the identification of meteorite fragments ejected by hypervelocity impacts on Mars. Images of Mars displayed land-forms wrought in the past by voluminous floodwaters, similar to those of the long-controversial Channeled Scablands of Washington State, USA. The record on Mars confirmed catastrophic flooding as a significant geomorphic process on at least one other planet. The first views of the Earth photographed by the crew of Apollo 8 gave us the concept of 'Spaceship Earth' and heightened international concern for protection of the global environment.

Mainstream geology is founded upon uniformitarian concepts enunciated by James Hutton (1726–1797) and Charles Lyell (1797–1875), who argued that, during unlimited expanses of time, the Earth has undergone slow, ceaseless change by processes we can observe in operation. In their view, we cannot call on any powers that are not natural to the globe, admit of any action of which we do not know the principle, nor allege extraordinary events to explain a common appearance. A hypervelocity meteorite impact is an extraordinary event, originating from outside the Earth, and wreaking change instantaneously. Such a process violates every tenet of uniformitarianism. Largely for this reason, hypotheses of impact origin for craters on the Earth and the moon were vigorously opposed for the better part of the past century. Space-age research now has established beyond doubt the authenticity of impact as a geologic process, but an abundance of evidence exists that a wide chasm still persists between the views of impact specialists and those of terrestrial geologists. A full realization of the ramifications of impact processes may have been delayed by the advent of plate tectonics, which engulfed the geological community in the late 1960s. Revolutionary as it appeared at that time, plate tectonics, which is envisioned as involving gradual changes generated by forces internal to the globe, fully conforms with uniformitarian principles. In contrast, impact processes, which have recently been cited to account for cataclysmic events such as massive tsunami deposits, incinerating wildfires, and global extinctions, carry genuinely revolutionary implications that are fatal to the uniformitarian principle itself.