Christian Jansen

Christian A. Jansen

Westfälische Wilhelms-Universität Münster - Planetology

Wilhelm-Klemm-Strasse 10, D-48149 Münster, Germany
E-Mail: christian.jansen@uni-muenster.de
 

About Me

I'm Christian and I come from Frankfurt am Main, Hesse, central Germany. I'm currently completing my MSc degree in geosciences at the University of Münster (WWU). Within the TRR 170, I’m responsible for managing and updating this website's content.

Since undergraduate studies at Goethe-University in Frankfurt my passion for early solar system research grew, which was only confirmed when I had the chance to conduct my first "real" science project as part of my BSc thesis. At that time I became especially intrigued by isotopes as natural tools to unravel the history of our solar system. In order to dive deeper into this field, I chose Münster University for my graduate studies and joined the cosmochemistry and isotope geochemistry group at the Institute for Planetology (WWU Münster). 

When I'm not in the lab, I’m a keen small-scale vegetable gardener and beekeeper, hobby classic car mechanic, and usually up for a couple of darts or pool matches with colleagues after work.

Cosmochemistry

In cosmochemistry research, we use meteorites (rocks that naturally fell to Earth from space) to study the early solar system. The meteorites I study are chondrites, which are 'space sediments' containing dust from the cloud of material that surrounded the infant sun – the solar nebula. They contain some of the earliest-formed solids of our solar system, preserved in nearly unaltered condition since their formation. By studying the chemical and isotopic composition of different chondrite components, we can infer when and under which conditions these objects formed, and how they were transported and mixed in the early solar system. This information allows to track the dynamical evolution of the early solar system, and ultimately helps to constrain the compositional range and origin of materials in the formation region of the terrestrial planets.

From comprehensive studies of nucleosynthetic isotope anomalies in bulk meteorites pursued within the last decade, we know that the early solar system was divided into two distinct nebula reservoirs, referred to as carbonaceous (CC) and non-carbonaceous (NC) reservoir, which likely represent the disk regions beyond and within the orbit of proto-Jupiter, respectively. This dichotomy is probably a primordial signature inherited from the solar system's parental molecular cloud, that is preserved in very diluted form in bulk meteorites. Measurements of individual components in chondrites, e.g., Ca,Al-rich inclusions (CAIs) and chondrules, reveal a significantly larger isotopic variability of these materials compared to bulk meteorites, thus offering important means to identify potential mixing end-members, and to infer mechanisms of transport and mixing in the disk. CAIs define a reservoir enriched in neutron-rich isotopes of many elements, while NC materials define the most depleted reservoir. CC material lies in between the two, suggesting that mixing of isotopically CAI-like and NC-like material causes the NC–CC dichotomy. This is also supported by the abundance of CAIs in CC chondrites and their near-absence in NC chondrites. The fundamental bimodality of planetary materials in multi-elemental isotope space suggests that mixing between NC and CC material was either completely blocked or insignificant. In contrast, some models of terrestrial planet formation (e.g., the pebble accretion model) argue for significant contribution of outer solar system material to the inner solar system. This has even been used to explain the origin of Earth's water, i.e., delivery of volatiles by carbonaceous and/or comet-like material in the late stages of Earth's accretion. In general, the extent of material exchange between the NC and CC reservoirs, i.e., the permeability of the "Jupiter barrier", as well as its importance for contributing outer solar system building blocks to the formation region of the terrestrial planets are not well known. Isotopes in chondrites are prime tools to investigate these issues in a quantitative way.

Projects

My research is currently focused on the isotopic composition of chondrules, millimeter-sized igneous spherules of remarkable compositional and textural diversity, which are formed by melting of aggregated dust in the protoplanetary accretion disk. As such, they provide a snapshot of the dust composition in the disk at the location and time of their formation. They are a main constituent of most primitive (chondritic) meteorites, which represent the building blocks of larger rocky objects like asteroids and the terrestrial planets of our solar system. With this project, we want to explore the chemical and isotopic variability of chondrules with state-of-the-art, highly precise analytical techniques, and use this information to evaluate (i) the importance of mixing between CC and NC materials, i.e., the nature and permeability of the "Jupiter barrier"; (ii) genetic relationships between chondrules, CAIs, and bulk meteorites; and (iii) the contribution of outer solar system material to the inner solar system and the formation region of the terrestrial planets.

Analytical Methods

The analytical methods and instruments I mainly use at the Institute for Planetology in Münster are:

Mass spectrometry 

MC-ICP-MS (ThermoScientific NeptunePlus); TIMS (ThermoScientific TritonPlus)

Electron microscopy and EDX 

SEM (JEOL JSM-6610LV)

 

 
Publications

[1] Jansen, C.A., Brenker, F.E., Zipfel, J., Pack, A., Labenne, L., Nagashima, K., Krot, A.N., Bizzarro, M., Schiller, M. (2019): Mineralogy, petrology, and oxygen isotopic composition of Northwest Africa 12379, metal-rich chondrite with affinity to ordinary chondrites. Geochemistry – Chemie der Erde 79, 4, 125537. https://doi.org/10.1016/j.chemer.2019.125537

     
    Conference Contributions

    [1] Jansen, C.A., Brenker, F.E., Krot, A.N., Zipfel, J., Pack, A., Labenne, L., Bizzarro, M., Schiller, M. (2019): Mineralogy, petrology, and oxygen isotopic composition of Northwest Africa (NWA) 12379, a new metal-rich chondrite with affinity to ordinary chondrites. Abstract #2741. Contributed to the 50th Lunar and Planetary Science Conference, The Woodlands, TX, USA. Abstract: https://www.hou.usra.edu/meetings/lpsc2019/pdf/2741.pdf – E-Poster: https://www.hou.usra.edu/meetings/lpsc2019/eposter/2741.pdf