Project Areas and Subprojects
Summary TRR 170 (2016-2024)
The major theme of the collaborative research centre TRR 170 'Late Accretion onto Terrestrial Planets' was to understand the late growth history of the terrestrial planets, from the last giant collisions of Moon- or Mars- sized planetary embryos to the subsequent late bombardment with smaller objects. This period of planet formation is critically important for understanding the formation of the terrestrial planets, their early chemical differentiation, and for constraining the parameters that controlled the subsequent evolution of planetary mantles, crusts and atmospheres. To improve our fragmentary understanding of these topics, TRR 170 applied a multidisciplinary approach that combines expertise in geochemistry and petrology, remote sensing and planetary geology, and geodynamic and impact modelling. TRR 170's research program provided novel insights into the timing and rates, chemical budget, and geodynamic implications of late accretion and constrained the physicochemical boundary conditions during the relevant time interval. In addition, some projects developed new approaches to study the early evolution of planetary building materials in the early protoplanetary disk from which the planets formed. Specifically, we (1) constrained the timing and distribution of basin-forming impacts on the Moon to improve basic parameters of the cratering chronology in the inner solar system, (2) quantified the mass, provenance and chemical composition of materials accreted to Earth and Moon between 4.57 and 3.8 billion years ago, (3) determined how the compositions of Earth, Moon and Mars were modified during accretionary impacts and volatile loss processes, (4) assessed how elements with different chemical properties were distributed within the growing terrestrial planets and how this changed their subsequent evolution, and (5) developed quantitative models for the thermal evolution of the early mantle, crust and atmospheres of the terrestrial planets, including the formation of and interaction between magma ocean, crust and early atmosphere in the relevant time interval. The combined results refined our understanding of several key processes during the early evolution of the terrestrial planets, such as the role of giant impacts in volatile loss processes and core formation, the development and evolution of magma oceans, the transition to solid-state convection, homogenization of chemical and isotopic heterogeneities, and the cooling history of the terrestrial planets. The TRR 170-DB data repository established by the data infrastructure project follows “FAIR” principles and secures long-term preservation, exchange and reuse of research data generated in TRR 170. TRR 170's successful integrated graduate program supported the education of the next generation of planetary scientists, with a particular emphasis on the multidisciplinary character of modern planetary sciences.
Summary of main results of the first and second funding period
During the first funding period, substantial efforts went into the initial setup and validation of new laboratory methods, numerical models and improved software for crater counting and statistics and their testing and benchmarking. The initial scientific results (reported in the 2019 funding proposal) yielded new data and progress in the geochronology of impactites, new relative and absolute model ages of basins from crater size frequency distributions, modeling of ejecta distribution, identification of chemical and isotopic variations of late accreted materials, metal-sulfide-silicate partitioning data, the physical processes during core formation, convection and crystallization of lunar and terrestrial magma oceans and the formation of early crust and dense atmospheres. Findings of the second funding period can be summarized as follows. Various results suggest that approximately exponential decay of a leftover population of planetesimals may be at present the best model for the late accretion flux in the inner solar system after lunar formation. The composition of the late accreted material on Earth and Moon was broadly similar to the material that accreted during the main phase of accretion; however, the composition and proportion of carbonaceous material remains uncertain. Various sample-derived data and new geophysical models yielded significant progress on the composition of the Moon and its reservoirs (including magma ocean composition and solidification time), core formation processes and the early terrestrial mantle, crust and atmosphere composition.
Project areas and subprojects:
The overarching goal of project area A was to quantify the inner solar system’s impactor flux during late accretion, by reconstructing the cratering record of the Moon and the chronology of its crust.
Results indicate the great potential of isotopic dating by improved isochron and in situ U-Pb methods to better understand the behavior of these systems in lunar impactites (subproject A1). Coupling of different methodological approaches such as CSFD-based chronology (subprojects A2 and A3), isotopic dating, modeling of gravity combined with topography data, crater and ejecta formation, and the progressive mixing of impact melt into the lunar crust as a consequence of impact gardening (subproject A4) proved to be a promising strategy to achieve project area A's long-term goal.
Major research objectives and questions
- Can a chronological bias between Ar-Ar and U-Pb for lunar impactites be verified with further analyses, and when did the oldest known basins on the Moon form? (subprojects A1, A5)
- How is the chronology and preservation of lunar crust related to the cratering record of the lunar surface? (subprojects A1, A4, A5, C4)
- What is the complete inventory of detectable impact basins and their sequence of formation on the Moon, and how were basin ejecta distributed on the lunar surface? (subprojects A1, A4, C4)
- What are the accurate absolute model ages of lunar basins derived from an improved lunar production function, and how does this compare to the chronology of lunar impactites and the lunar crust? (subprojects A2, A1, A5)
- Are morphologies of basins on Mercury consistent with our lunar-based models of basin formation, and are crater records on Mercury consistent with models of the size distribution of the impactor population(s) and the timing of the inner solar system’s impactor flux? (subproject A6)
A1 - Chronometric investigations of ancient lunar impact rocks (2016-2024).
Principal investigators: Harry Becker, Erik E. Scherer
Doctoral students: Tobias Dürr, Dennis Vanderliek
Postdocs and other scientists: Ana Cernok, Thomas Haber, Anne Lindner, Jasper Engelmann
A2 - Constraining the age of the South Pole–Aitken basin and the lunar landing sites – implications for the lunar chronology (2016 – 2024).
Principal investigator: Harald Hiesinger
Doctoral students: Wajiha Iqbal, Astrid Oetting
A3 – Ancient bombardment of the inner solar system – Reinvestigation of the “fingerprints” of different impactor populations (2016 – 2019).
Principal investigators: Thomas Kneissl, Harry Becker
Doctoral students: Csilla Orgel, Christian Riedel
A4 - Formation and evolution of large impact basins on the moon (2016 – 2024).
Principal investigators: Jürgen Oberst, Kai Wünnemann
Doctoral students: Tomke Lompa, Tiantian Liu, Valeria Montejo Melgarejo, Daniel Wahl
Postdoc: Tiantian Liu
Fellow: Haifeng Xiao
A5 – Chronology of lunar crust formation and its relation to the age of the Moon (2020 – 2024).
Principal Investigators: Doris Breuer, Thorsten Kleine, Stephan Klemme
Postdocs: Sabrina Schwinger, Max Collinet
Doctoral Students: Cordula Haupt, Jonas Schneider
A6 – Comparative morphologies, ejecta plains, and ages of impact basins on the Moon and Mercury (2020 – 2024).
Principal Investigators: Harald Hiesinger, Jürgen Oberst
Doctoral Students: Barbara Giuri, Claudia Szczech
The main goal of project area B was to determine the provenance and chemical composition of accreted material in the terrestrial planet region, whether and how the characteristics of the material changed with time, and how planetary compositions were modified during accretionary impacts and magma degassing.
Results obtained during the first funding period demonstrate that this goal can be reached through a combination of isotopic and chemical analyses of meteoritic and planetary samples. The results, together with various other studies, also reveal, however, that core formation and presumably also degassing on planetary precursor bodies may have obscured the chemical and isotopic signatures of planetary building blocks. As a consequence, specific chemical or isotopic signatures may provide seemingly contradictory constraints on the provenance and composition of late-accreted materials. Understanding the nature and origin of late-accreted materials, therefore, requires a multifaceted approach that combines different chemical and isotopic observations in a mutually consistent way.
Major research objectives and questions
- What was the composition of Earth, Moon, and Mars before late accretion, and was it volatile rich or volatile poor? (subprojects B1, B2, B3, B6, B7, B8)
- How does the late accretion history on Mars compare with Earth? (subprojects B3, B6)
- How did the provenance and composition of the planetesimal population in the terrestrial planet region and the asteroid belt change over time? (subprojects B3, B5, B6)
- Were volatile element depletions in (building materials of) terrestrial planets caused by planetary degassing or inherited from thermal processing in the solar nebula? (subprojects B1, B7, B8)
B1 - Origin of fractionations of highly siderophile and siderophile volatile elements in lunar rocks and in the Earth (2016 – 2024).
Principal Investigator: Harry Becker
Postdocs: Philipp Gleißner, Guillaume Florin
Fellows: Marion Defrance, Chunhui Li, Julie Salme, Mathias Schannor, Zaicong Wang
B2- Stable isotope fractionation of S, Te and Pd and the roles of core formation and late accretion on siderophile volatile elements in the Earth (2016 – 2019).
Principal Investigators: Harry Becker, Thorsten Kleine/Mario Fischer-Gödde, Stephan Klemme
Doctoral Students: Jan Hellmann, Timo Hopp, Franziska Schmid
Postdoc: Tobias Grützner
B3 - Tracing the origin of the late veneer using nucleosynthetic isotope anomalies in siderophile elements (2016 – 2024).
Principal Investigators: Thorsten Kleine, Emily Worsham
Postdoc: Jonas Pape
B4 – The atmo- hydrophile element (H and halogens) inventory of the Earth and Moon (2016 – 2019).
Principal Investigators: Timm John, Stephan Klemme, Andreas Stracke
Doctoral Student: Stamatis Flemetakis
B5 - Early-formed, volatile-rich clasts in meteorite breccias: building materials of the terrestrial planets (2016 – 2024)?
Principal Investigators: Addi Bischoff, Timm John
Doctoral Students: Samuel Ebert, Markus Patzek, Jakob Storz, Robbin Visser
Fellow: Aelita Girich
B6 – Comparing the (late) accretion history of Mars and Earth – timing, sources, dynamics (2020 – 2024).
Principal Investigator: Christoph Burkhardt
Doctoral Student: Fridolin Spitzer
Postdoc: Jason Woo
B7 – Experimental and isotopic investigations of volatile element loss during magma degassing (2020 – 2024).
Principal Investigators: Christoph Burkhardt, Stephan Klemme
Doctoral Student: Elias Wölfer
Postdocs: Stamatis Flemetakis, Christian Renggli
B8 – Is the depletion of the moderately volatile elements in the Earth inherited from nebular processes (2020 – 2024) ?
Principal Investigators: Harry Becker, Timm John
Doctoral Students: Ann-Kathrin Krämer, Maxence Regnault, Julie Salme
Fellows: Cécile Deligny, Simon Hohl, Ke Zhu
The main goal of project area C was to obtain a quantitative understanding of the interplay between impact and magma ocean processes during the late stages of terrestrial planet accretion, by determining how impacts contributed to magma ocean formation and their subsequent evolution, and how magma ocean processes affected the distribution of late-accreted materials and the resulting composition of planetary mantles.
We combined laboratory experiments and the chemical and isotopic analyses of lunar and terrestrial samples with numerical modeling of dynamic processes, such as impacts, mantle convection and differentiation, and mantle degassing and atmosphere evolution.
Major research questions and objectives
- How were siderophile volatile elements redistributed between core-forming melts and mantle minerals, and how did this affect the composition of the mantles of Earth and Mars? (subproject C1)
- How was impactor material accreted, incorporated, and mixed into the terrestrial planets, and how does this depend on their thermal evolution? (subprojects C2, C3, C4)
- How did giant impacts contribute to the formation of magma oceans and their subsequent evolution? (subprojects C2, C4)
- How did magma ocean crystallization affect dynamic processes within the Earth’s and lunar interior? (subprojects C1, C3, C4, C6)
- How were atmosphere and crust formation processes coupled during the early evolution of Earth and Mars? (subprojects C2, C5, C6)
C1 - Partitioning of siderophile volatile elements during core formation (2016 – 2024).
Principal Investigator: Arno Rohrbach
Doctoral Students: Dominik Loroch, Sebastian Hackler, Paul Pangritz
Fellow: Edgar Steenstra
C2 - Modelling giant impacts and the subsequent thermochemical evolution of liquid metal in a convecting magma ocean (2016 – 2024).
Principal Investigators: Ulrich Hansen, Kai Wünnemann
Doctoral Students: Nicole Güldemeister, Lukas Manske, Christian Maas, Philipp Kreielkamp
Postdocs: Nicole Güldemeister, Laetitia Allibert
C3 - Preservation of 182W heterogeneities in the Earth's mantle – implications for the timing and nature of late accretion (2016 – 2024).
Principal Investigators: Ulrich Hansen, Thorsten Kleine, Andreas Stracke
Doctoral Students: Max Winkler, Sabine Dude
Postdoc: Gregory Archer
Fellows: Paul Béguelin, Martijn Klaver, Seema Kumari
C4 - From the Moon-forming impact to the era of late bombardment: the thermochemical evolution of the early Earth–Moon system (2016 – 2024).
Principal Investigators: Doris Breuer, Ulrich Hansen, Kai Wünnemann
Doctoral Students: Irene Bernt, Randolph Röhlen, Thomas Wiesehöfer
Fellow: Maxime Maurice
C5 - Early interior–surface–atmosphere interactions on the terrestrial planets (2016 – 2024).
Principal Investigators: Heike Rauer, Frank Sohl, Kai Wünnemann
Doctoral Students: Nisha Katyal, Gianluigi Ortenzi
Postdoc: Iris van Zelst
C6 - Formation and evolution of crust on early Earth (2020 – 2024).
Principal Investigators: Lena Noack, Frank Sohl
Doctoral Students: Julia M. Schmidt, Caroline Brachmann
Z Central Administration of CRC 170 (2016 – 2024)
Spokespersons: Harry Becker, Harry Hiesinger, Thorsten Kleine
Executive Board members: Harry Becker, Doris Breuer, Harry Hiesinger, Thorsten Kleine, Stephan Klemme, Jürgen Oberst, Emily Worsham, Christoph Burkhardt, Kai Wünnemann
Coordination: Carolyn van der Bogert, Elfrun Lehmann, Katharina Heinze, Sabine Hunze, Iris Weber
Doctoral Student Representatives: Ann Kathrin Krämer, Csilla Orgel, Julia M. Schmidt, Jonas Schneider,