Mars is about one-eighth the mass of the Earth and it may provide an analogue of what the Earth was like when it was at such an early stage of accretion. The fur ther growth of the Earth was sustained by major collisions with planetesimals and planets such as that which resulted in the formation ofthe Earth's moon (Hartmann and Davis, 1975; Cameron and Ward, 1976; Wetherill, 1986; Cameron and Benz, 1991). This late accretionary history, which lasted more than 50 Myr in the case of the Earth (Halliday, 2000a, b), appears to have been shorter and less catastrophic in the case of Mars (Harper et ai. , 1995; Lee and Halliday, 1997). In this article we review the basic differences between the bulk composition of Mars and the Earth and the manner in which this plays into our understanding of the timing and mechanisms of accretion and core formation. We highlight some of the evidence for early cessation of major collisional growth on Mars. Finally, we reevaluate the isotopic evidence that Mars differentiated quickly. Fundamental differences between the composition of Mars and that of other terrestrial planets are apparent from the planet's slightly lower density and from the compositions of Martian meteorites. The low density is partially explicable if there is a greater proportion of more volatile elements.

Volume 60 of Reviews in Mineralogy and Geochemistry assesses the current state of knowledge of lunar geoscience, given the data sets provided by missions of the 1990's, and lists remaining key questions as well as new ones for future exploration to address. It documents how a planet or moon other than the world on which we live can be studied and understood in light of integrated suites of specific kinds of information. The Moon is the only body other than Earth for which we have material samples of known geologic context for study. This volume seeks to show how the different kinds of information gained about the Moon relate to each other and also to learn from this experience, thus allowing more efficient planning for the exploration of other worlds.

In this comprehensive overview of Man’s relationship with his planet’s nearest neighbor, David Harland opens with a review of the robotic probes, namely the Rangers which returned television before crashing into the Moon, the Surveyors which 'soft landed' in order to investigate the nature of the surface, and the Lunar Orbiters which mapped prospective Apollo landing sites. He then outlines the historic landing by Apollo 11 and the final three missions of comprehensive geological investigations. He concludes with a review of the robotic spacecraft that made remote-sensing observations of the Moon. This Commemorative Edition includes a foreword by one of the original astronauts as well as an extra section reviewing the prospect of renewed exploration there. New graphics and images are also included.

The only work to date to collect data gathered during the American and Soviet missions in an accessible and complete reference of current scientific and technical information about the Moon.