Tobias Owen

Thérèse Encrenaz

Johannes Geiss

R. Kallenbach

Konrad Mauersberger

François Robert

Proceedings of an ISSI Workshop, 14-18 January 2002, Bern, Switzerland

Volume Resulting from an Issi Workshop, 14-18 January 2002, Bern, Switzerland

Solar System History from Isotopic Signatures of Volatile Elements

W.K. Hartmann

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.

Proceedings of an ISSI Workshop, 10–14 April 2000, Bern, Switzerland

Chronology and Evolution of Mars

Willy Benz

Günter Lugmair

The workshop "From Dust to Terrestrial Planets" was initiated by a working group of planetary scientists invited to ISSI by Johannes Geiss in November 1997. The group split to focus on three topics, one of which was the history of the early solar system, including the formation of the terrestrial planets in the inner solar system. Willy Benz, Gunter Lugmair, and Frank Podosek were invited to convene planetary scientists, astrophysicists, and cosmochemists to synthesize the current knowledge on the origin and evolution of our inner planetary system. The convenors raised the interest of scientists from all over the world in the detailed assessment of the available astronomical, chronological, geochemical and dynamical constraints of the first period of inner solar system evolution. In partic ular, this included appraisal of the newest results from astronomical observations by the Hubble Space Telescope, the Infrared Space Observatory, and other space and ground-based facilities of solar-like systems and nebular disks, possibly repre senting early stages of the solar accretion disk and planet formation. At the same time, the current models of the origin, evolution, transport, and accretion processes of circum stellar disks were presented. This included the new insights provided by the recent discovery of extrasolar giant planets, which were considered insofar as they are relevant to the overall dynamics of the inner part of the solar system.

Proceedings of an ISSI Workshop, 15–19 February 1999, Bern, Switzerland

From Dust to Terrestrial Planets

Volume Resulting from an ISSI Workshop 14–18 January 2002, Bern, Switzerland

J.W. Bieber

E. Eroshenko

P. Evenson

E.O. Flückiger

This book summarizes the results from the detection of cosmic rays at the surface and in the lower atmosphere of Earth during the fifty years since the invention of the neutron monitor by John A. Simpson in 1948. The properties of solar and galactic cosmic rays in the heliosphere, such as Forbush decreases, modulations by solar and heliosphere parameters, the physical processes that govern them, and their connection to Space Weather, are reviewed. This interdisciplinary compilation provides links between cosmic ray physics, geophysics, terrestrial climate, and human activity and health.

Cosmic Rays and Earth

R. Kallenbach

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