Evolution of organic matter in the early solar system

A black and white image of a asteroid with black space in the background

Asteroid Bennu ejecting particles from its surface on Jan. 6, 2019, images taken by the NavCam 1 imager aboard NASA's OSIRIS-REx spacecraft 

The delivery of extraterrestrial organic molecules to the inner solar system by asteroids and comets is widely considered to have seeded the early Earth, and potentially the other rocky inner solar system planets, with prebiotic molecules that went on to play a crucial role in formation of life. 

Indeed, this idea is one of the motivating driving forces behind the JAXA Hayabusa2 mission that successfully returned samples of the primitive asteroid Ryugu in December 2020, and the NASA OSIRIS-REx mission that successfully collected materials from the surface of asteroid Bennu and is scheduled to return in 2023.

However, pristine carbonaceous chondrite meteorites represent a more immediate mechanism through which asteroid composition, geological history, and abiotic processing of primitive organic matter can be studied.

Prebiotic organic matter has been partially preserved within the complex fine-grained matrix of these meteorites recording snapshots of events and processes that occurred 4.5 billion years ago and shaped our solar system.

Through the application of advanced analytical techniques, we can assess the origins and roles of mineral transformation and aqueous and thermal processing on the molecular inventory of the organic matter delivered to the early Earth.

An elemental X-ray map

An elemental X-ray map of the CO3.0 carbonaceous chondrite DOM 08006 collected on a scanning electron microscope by Enrica Bonato of the Planetary Materials Group at the Natural History Museum. Chondrules and silicate fragments 10s of microns in size are bound together by a very fine-grained matrix of amorphous and crystalline minerals and carbonaceous materials.

 

Blue = Si; green = Mg; red = Fe.

The fine-grained matrix of these pristine carbonaceous chondrites comprises a heterogeneous mixture of submicron sized crystalline and amorphous silicates, oxides, sulphides and metal.

The mineralogy and chemistry of the fine-grained matrix that preserves these primitive carbonaceous materials varies across meteorite groups of carbonaceous chondrites, and in doing so provides a broad record of the chemical and physical processes that were active during accretion and early parent body processing.

Crucially, this matrix also contains up to ~4 wt.% total organic carbon including a wide variety of organic materials such as soluble organic matter (SOM), unstructured, kerogen-like insoluble organic matter (IOM), and carbonaceous nanoglobules. 

The interstellar or outer solar system origins of this organic matter are strongly debated with the issue further complicated by aqueous and/or thermal alteration on parent bodies.

Bulk extraction studies have revealed that the extractable SOM comprises a range of relatively small organic molecules including amino acids, carboxylic acids and various aromatic species.

The remaining IOM, which represents between 70% and >90% of the OM, is more complex with large macromolecular chain- and ring-components dominating over smaller molecules and species.

However, in order to understand the origin of the OM we need to correlate its complex molecular composition to its local mineralogical and geochemical environment at the nano-scale.

The project

This study explores the complex and heterogeneous nature of primitive organics within the context of the submicron grain sized matrix minerals. By doing so the study explores the research questions:

  • How did the OM molecular composition vary spatially within the early forming solar system?
  • How did this OM evolve as a function of aqueous and thermal alteration?

To achieve this the project will apply a suite of state-of-the-art imaging techniques such that in-situ chemical, spectroscopic and diffraction information from the same samples can be combined. By correlating all these analyses, the individual grain properties and the inter-grain relationships between the OM and minerals can be understood. 

The student will become integrated into the Planetary Materials Group at the Natural History Museum and the Planetary Sciences Group at Royal Holloway University of London, and have the opportunity to study meteorites from one of the finest meteorite collections in the world at the Natural History Museum.

Electron microscopy, including scanning and transmission electron microscopy (SEM and TEM), infrared, Raman and fluorescence spectroscopy, and thermal analysis will be performed in house at the Museum’s Image and Analysis Laboratories and at Royal Holloway University and the Institut für Mineralogie, Münster University, Germany. Micro- and nano-scale X-ray and infrared spectromicroscopy will be undertaken at international facilities such as the UK’s Diamond Light Source and nanoscale electron imaging and spectroscopy at the UK’s Daresbury superSTEM. 

We seek an enthusiastic person for this project with a strong background in the physical sciences or planetary sciences or geology, and with an interest in applying analytical mineralogy to a planetary science context.

Eligibility

To be classed as a home student, candidates must meet the following criteria:

  • Be a UK National (meeting residency requirements), or
  • Have settled status, or
  • Have pre-settled status (meeting residency requirements), or  
  • Have indefinite leave to remain or enter  

 If a candidate does not meet the criteria above, they would be classed as an International student.

Further guidance on UKRI Eligibility Criteria can be found on the UKRI website

How to apply

Please send the following documents to Anna Hutson (postgradoffice@nhm.ac.uk)

  • Curriculum vitae
  • Covering letter outlining your interest in the PhD project, relevant skills training, experience and qualifications, and a statement of how this PhD project fits your career development plans.
  • Transcripts of undergraduate and Masters degree results.
  • Two academic references including (if applicable) Masters project supervisor.

Apply for this project

This is an Science and Technology Facilities Council (STFC) funded studentship.

Read the eligibility criteria and application guidance below, then send your application to postgradoffice@nhm.ac.uk.

Application deadline: 29 January 2021

Any questions?

Natural History Museum

Paul Schofield

Supervisors

Natural History Museum

Paul Schofield

Ashley King

Sara Russell

Royal Holloway University of London

Queenie Chan 

Westfälische Wilhelms-Universität, Münster

Christian Vollmer

We welcome applications from everyone

We offer a stimulating and professional environment in which to work. We look for staff who can work according to our values: diversity, creativity, connection and evidence-based thinking. 

A cartoon diagram from astrochem.org describing the relationship between interstellar dust and primitive organic matter prior to accretion on an asteroid.

References and reading

JAXA’s Hyabusa2 mission 

NASA’s OSIRIS Rex mission 

Pizzarello S., Cooper G.W., Flynn G.J. (2002) The Nature and Distribution of the Organic Material in Carbonaceous Chondrites and Interplanetary Dust Particles. In: Meteorites and the Early Solar System II (Editors: D. S. Lauretta and H. Y. McSween) pp. 625-651.

Vollmer C., Leitner J., Kepaptsoglou D., Ramasse Q., King A.J., Schofield P.F., Bischoff A., Araki T. and Hoppe P. (2020) A primordial 15N-depleted organic component detected within the carbonaceous chondrite Maribo. Nature Scientific Reports 10:20251 

Kebukawa Y., Zolensky M.E., Kilcoyne A.L.D., Raham Z., Jenniskens P., Cody G.D. (2014) Diamond xenolith and matrix organic matter in the Sutter’s Mill meteorite measured by C-XANES. Meteoritics and Planetary Science 49 (11) pp. 2095-2103.

Martins Z. (2011) Organic chemistry of carbonaceous meteorites. Elements 7(1) pp. 35-40.

Relevant issues of Elements Magazine:

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