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Prof. Dr. Addi (Adolf) Bischoff

Westfälische Wilhelms-Universität Münster - Planetology

Principal Investigator

Institut für Planetologie, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany, Tel.: 0251-8333465

 

B5 Summary

One intriguing aspect of our solar system’s history is how and when Earth and the other terrestrial planets received their volatile components. Currently, we know that the solar system’s planetary bodies were likely made up of materials that are similar to components present in approximately 30 silicate-rich undifferentiated and differentiated meteorite groups. Some of these potential building blocks¾including comets, Kuiper belt objects (KBOs), and water-bearing asteroids (the latter perhaps similar to the parent bodies of carbonaceous chondrites)¾contain volatiles and thus could have contributed the terrestrial planets’ atmo- and hydrophile volatile components. However, the total inventory of volatile components on Earth (and potentially on other terrestrial planets) cannot be explained by the addition of these materials.

Thus, another source must have contributed to Earth’s volatile content. One potential source might be a material found in meteoritic breccias. Within meteoritic breccias, volatile-rich extraterrestrial materials exist as lithic fragments, but these materials have not been identified as an individual type of meteorite. Instead, these volatile-rich fragments are often described in the literature as “dark clasts”. They vary in size from microscopic to macroscopic, and they are ubiquitous in chondritic (e.g., ordinary and Rumuruti, CM, CR, CH chondrites) and achondritic meteorite breccias (e.g., ureilites, aubrites, HED-meteorites).

Also, these dark clasts are mineralogical and chemically different from typical CI and CM chondrites, so they may yield insights into the types and compositions of volatile-rich materials that exist beyond those found in samples from known meteorite classes. Thus, because these dark clasts are found in all types of meteoritic breccias¾in chondritic breccias as well as in breccias from differentiated parent bodies¾they may represent some of the material that was scattered into the solar system and is perhaps related to giant planet migration (“Grand Tack”). This scattered material may have “contaminated” not only meteorite parent bodies, but also large planetary bodies like Earth.

Hence, the most important aim of the project is to determine if the composition of these dark clasts matches the volatile inventory of the Earth and potentially other terrestrial planets. Another important goal is to roughly decipher when these clasts and the corresponding breccias formed on their parent body, because this might provide insight into when they could have delivered volatiles to Earth. To meet these goals, the project will be subdivided into two parts: In the first part, we will examine the internal structure and the compositional variability of these dark clast materials, which will provide chemical details about the fragments’ constituents (we will analyse the stable isotopes of O, C, D/H, Cl and determine the halogen concentrations), and reveal how they might define their hosts’ bulk signals. The second part of the project will determine the bulk chemical characteristics of the clasts that may have contributed to the current volatile inventories of terrestrial planets (we will analyse major, minor, and trace elements and perform isotope analyses of N, D/H, O, and Cr). Overall, this subproject will complement the subproject B4, which will determine the atmo- and hydrophile inventory of the Earth and Moon, as well as subprojects B1-B3, which will determine the chemical compositions of late-accreted material. From this suite of highly coordinated subprojects, we may then be able to specifically quantify the amount of highly volatile elements that were added during late accretion. Thereby, understanding the general provenance of these volatile components¾as we aim to do here¾will shed light onto key historical processes that shaped Earth and the terrestrial planets.

B5-4