Welcome to the Noble Gas Cosmochemistry Group

Introduction

In this artist's concept, a narrow asteroid belt filled with rocks and dusty debris orbits a star similar to our own Sun when it was approximately 30 million years old. Quelle: NASA/JPL-Caltech.

We are a part of the Division of Space Research and Planetary Sciences (Abteilung für Weltraumforschung und Planetologie) within the Institute of Physics of the University of Bern. Together with our colleagues in the Theoretical Astrophysics and Planetary Science Group we are interested in the formation and evolution of planetary systems. Our particular expertise is in the measurement of noble gas isotopes, either to determine the cosmic-ray exposure ages of meteorites and lunar rocks or to study the trapped noble gases in extraterrestrial matter. These measurements allow us to obtain crucial information about i) the dynamics in the modern asteroid belt (of interest e.g. to assess the hazard that large meteorites might present to the Earth), ii) the long term variability of galactic cosmic-rays, and iii) the formation and evolution of the earliest objects in the solar system.

Why measure noble gases?

Artist's impression of the early solar nebula.

Noble gas, as their name indicate, usually do not undergo chemical reactions. Therefore, any changes in there elemental and isotopic compositions are directly connected to physical processes, i.e. diffusion, solution,... Therefore, if we measure the noble gas record in meteorites we are able to obtain information about the physical conditions in the very early solar system like temperature and pressure, time of first solid formation, the effects of aqueous alteration ...

Because only tiny amounts of the noble gases (helium, neon, argon, krypton, and xenon - we do not measure radon) are present in rocks, their abundance and isotopic composition is altered measurably by processed that would otherwise go unremarked. For example, the interaction of the energetic particles known as galactic cosmic-rays with a rock results in the production of new (cosmogenic) nobles gases by nuclear reactions. Knowing the rate at which this occurs and by measuring the amount of cosmogenic noble gases in a meteorite we can calculate how long the meteorite has traveled in space before landing on Earth. This length of time is known as the cosmic-ray exposure age of a meteorite and is typically tens of millions of years for stony meteorites and hundreds of millions of years for iron meteorites.

Although nobles gases are present in rocks in very low abundances only (typically a few parts per billion), they can nevertheless be measured accurately and sensitively because they are chemically inert, making them easy to seperate and handle in a vacuum system.

Physics Institute, Space Research and Planetary Sciences
Sidlerstrasse 5, 3012 Bern, Switzerland

Tel: +41 (0) 31 631 4411
Fax: +41 (0) 31 631 4405