ANR BIOGEN

Abstract:

Tracking back the birth of terrestrial and extraterrestrial life by identifying the earliest organisms using robust geochemical biomarkers calibrated against known recent biological remains.

Project rationale:

In the era of Mars and asteroid sample return missions, it is imperative to find robust markers to establish the biogenicity of objects in ancient sediments and planetary materials. We are exploring correlations between Zn isotopic anomalies associated with fossil remains and organic biomarkers and other geochemical and isotopic signatures, bearing in mind that, in general, zinc is depleted in light isotopes in organic matter.

Challenges and objectives

Establish a set of reliable biomarkers to identify the biogenicity of objects present in ancient terrestrial sediments and planetary materials.

This interdisciplinary project aims to overcome the subjective nature of descriptive morphology in the determination of biogenicity by means of novel and innovative applications of well-established techniques (morphology, mineralogy, petrology, X-ray microtomography, synchrotron-induced X-ray fluorescence, rock and fossil geochemistry, high-precision Zn and Pb isotopes, C isotopes, MC-ICP-MS), synchrotron-induced X-ray fluorescence, rock and fossil geochemistry, high-precision Zn and Pb isotopes, C isotopes, MC-ICP-MS) combined with more exploratory techniques (high-precision S isotope analyses by MC-ICP-MS, organic biomarkers in very ancient rocks) to establish and verify the accuracy of a set of robust biomarkers, including a group of geochemical criteria (Zn, Pb, S, C), which can be used to reliably determine the biogenicity of putative organic remains, whether from objects present in ancient terrestrial sediments or planetary materials (meteorites and future samples returned from space missions).

Methods

Combine well-established and exploratory techniques in geochemistry, mineralogy and imaging and apply them to rocks and fossils of different ages and locations from the geological record of life.

We combine well-established techniques (mineralogy, geochemical analyses of rocks and fossils, stable Zn isotopes, radiogenic Pb isotopes, MC-ICP-MS, neutron fluence determination using Sm and Gd isotope anomalies, X-ray microfluorescence, synchrotron) with more exploratory techniques (high-precision S isotope analyses by MC-ICP- MS, organic biomarkers in very ancient rocks) to the analysis of rocks and fossils from reference sites in the Francevillian Paleoproterozoic series in Gabon, fossils from the Cambrian Burgess Shale in Canada and diatomites and their fossils from the Miocene volcanic cone of Andance in France. In addition, we will have to return to geochronology and select samples from Gabon that have not been irradiated by the Oklo natural reactor. In addition, we plan to extend the project to include Zn isotope measurements of (i) carbonates over time to try to understand the Zn cycle running through Earth’s history and (ii) modern biomass, such as mosses and plants, to compare the Zn isotope signature of fossils of putative biological origin with biological material of certain biological origin.

Results

Ongoing project….

List of LGL-TPE participants:

Formally involved in the project:

• Janne Blichert-Toft,
• Guillemette Menot,
• Francis Albarède,
• Philippe Télouk,
• Emmanuelle Albalat,
• Salomé Ansanay-Alex,
• Marine Pinto

Informally involved in the project:

• Aline Lamboux,
• Florent Arnaud-Godet

Students involved in the project:

• Emilien Decaux (M2 and PhD),
• Baptiste Coutret (PhD)