Distribution of HYdrogen in the protoplanetary Disk and deliveRy to the Terrestrial planEts – HYDRaTE

For the most hydrated samples, we are using a method based on in-situ measurements of the C/H and D/H ratios by SIMS to estimate the isotopic composition of water-bearing minerals. This method, recently developed by HYDRaTE's PI, allows for the first time the D/H ratios of hydrous chondritic minerals to be determined without hindrance from hydrogen in adjacent organic materials. Coupled with ion imaging for measuring the D/H composition of organic particles, this permits an exhaustive assessment of the origin of volatile-rich molecules in primitive Solar System materials. We investigated the distribution of hydrogen in the major high-temperature components of chondrites, the chondrules, via laboratory experiments and analytical measurements. We built experimental devices to melt and crystallize chondrule analogues under conditions close to those estimated for the protoplanetary disk (low total pressure, low oxygen fugacity) and high partial pressures of H2 and/or H2O. Through these experiments, we studied the consequences of the presence of hydrogen-rich gases on chondrule formation and provide thermodynamical data on hydrogen partitioning and isotopic fractionation under conditions close to those estimated for the protoplanetary disk. These experimental results were compared to the hydrogen compositions of natural samples. Indeed, a major achievement of HYDRaTE is to quantify the hydrogen abundance and isotopic composition of chondrule silicates, with particular focus on enstatite chondrites, the best candidate for the Earth's building blocks, and to estimate the contribution of the different categories of chondrites to the H budget of Earth and the other terrestrial planets.

- We have determined the water D/H ratio in different types of carbonaceous chondrites (CM, CI, CO, CR, ungrouped) using a method recently developed on SIMS (Piani et al. 2018, Nat. Astro). We show that the D/H variations of water and organics in the different chondrite types are not the result of parent body processes, and we propose a model to explain this distribution in the disk at the time and place of the chondrite parent formation. This work has been published in Earth and Planetary Science Letters in May 2021 (Piani et al., EPSL 2021).

- The “D/H vs. C/H” method has also been applied to other chondritic samples to determine the isotopic composition of hydrogen carriers in these objects: grains of the carbonaceous asteroid Ryugu brought back by the JAXA Hayabusa2 space mission, whose water has an isotopic composition close to that of CI-type carbonaceous chondrites (Piani et al., ApJ 2023), ordinary chondrites showing extreme D/H isotopic variations (Grant et al., GCA 2024) and, during 2024, on grains from the asteroid Bennu brought back by NASA's OSIRIS-REx space mission (Piani et al., MetSoc meeting 2024).

- Enstatite chondrites are considered to be good analogues of the rocks that mostly formed the Earth. One of the first tasks of the HYDRaTE project was to analyze the content and isotopic composition of hydrogen in a dozen total rock enstatite chondrites, then to locate one of the hydrogen-bearing phases using in situ ion probe analysis. The results show that these meteorites could have contributed at least three times the total amount of hydrogen present in the water of the Earth's oceans. The hydrogen isotopic composition of enstatite chondrites is in perfect agreement with that of the water stored in the Earth's primitive mantle. We also show that a large proportion of atmospheric nitrogen could also originate from enstatite chondrites, making these rocks, analogues of the Earth's main constituents, suppliers of the elements fundamental to the development of life on Earth. These results were published in the journal Science in August 2020 (Piani et al., Science 2020). Further analyses were carried out as part of Dorian Thomassin's PhD thesis, showing a link between hydrogen and sulfur in these chondrites and indicating the influence of sulfur-rich gases in the chondrite-forming environment of enstatite chondrites (Thomassin et al., EPSL 2024).

- This work has also led the researchers involved in HYDRaTE to participate in several review articles related to the project's themes (Izidoro & Piani, Elements 2022; Broadley et al., Nature review 2022; Krot et al., Sp. Sc. Rev. 2025).

Results from the HYDRaTE project indicate the presence of hydrogen in enstatite chondrites (ECs) and its link with sulfur (Piani et al., Science 2020; Thomassin et al., EPSL 2023). Organic matter in the matrix and glass in the chondrules (mesostasis) are the two carrier phases identified to date, but a recent study suggests that sulfur phases present in the fine-grained matrix may contain most of the hydrogen in ECs (Bryson et al. MetSoc 2023). An important prospect for the coming years is to refine our knowledge of the hydrogen-carrying phases of ECs. To this end, a project funded by the national planetology program is currently underway: a coupled study of the matrix and chondrules using electron microscopy, Raman spectroscopy and an ion probe. The aim of these observations is to establish a picture as exhaustive as possible of the phases carrying volatiles, so as i) to be able to determine the origin of these elements in the inner protoplanetary disk, and ii) to draw all the implications for planet formation.

Publications:

Vacher L.G., Piani L., Rigaudier T., Thomassin D., Florin G., Piralla M., Marrocchi Y. (2020). Hydrogen in chondrites: Influence of parent body alteration and atmospheric contamination on primordial components. Geochimica et Cosmochimica Acta 281, 53-66. DOI: 10.1016/j.gca.2020.05.007

Piani L., Marrocchi Y. , Rigaudier T. , Vacher L.G. , Thomassin D., Marty B. (2020) Earth’s water may have been inherited from material similar to enstatite chondrite meteorites. Science, Vol. 369, Issue 6507, pp. 1110-1113. DOI: 10.1126/science.aba1948

Piani L., Marrocchi Y., Vacher L. G., Yurimoto H., Bizzarro M. (2020) Origin of hydrogen isotopic variations in chondritic water and organics. Earth and Planetary Science Letters, Vol. 567, 117008. DOI: doi.org/10.1016/j.epsl.2021.117008

Communications:

Goldschmidt conference 2021 (invited talk) - Piani L., Marrocchi Y., Rigaudier T., Vacher L. G., Thomassin D., Marty M. Earth’s water may have been inherited from material similar to enstatite chondrite meteorites.

Invited seminar:

June, 2021 - TRR-170/Planetology Colloquium, University of Münster (online)

April, 2021 - Institute of Geological Sciences, University of Bern (online)

March, 2021 - Société Française d'Exobiologie (online & vidéo)

February, 2021 - ZJU Earth Data Webinar, Zhejiang University, China (online & video)

November, 2020 - Cosmochat at ETH Zurich (online)

October, 2020 - IPGP Paris, CAGE-group seminar (online)

February, 2020 - CNRS Winter School, Les Houches - Piani L., Chondritic water and volatils (solarsystem2020.wordpress.com/)

Hydrogen is the most abundant element in the solar system; nonetheless its distribution in the planetary solids remains poorly known and its origin on Earth and the other rocky planets enigmatic. HYDRaTE proposes to shed light on the distribution of hydrogen in the protoplanetary disk 4.56 billion years ago by studying the hydrogen-bearing phases of primitive solar system materials including primitive meteorites (chondrites), micrometeorites and dust particles retrieved from hydrated bodies by space missions. Conjugating the complementary skills of a team led by L. Piani at Centre de Recherches Pétrologiques et Géochimiques (CRPG) in Nancy and composed of lab managers, engineers, students, and of three external researchers, HYDRaTE will use a multifaceted approach to (i) estimate the hydrogen concentration and isotopic composition (D/H ratio) of H-bearing phases in extraterrestrial samples, (ii) experimentally determine the conditions in which hydrogen is incorporated in primordial dusts and, (iii) quantify the contribution of chondritic material to the hydrogen-budget of the Earth and other rocky planets. The project will benefit from the presence at CRPG of state-of-the-art analytical instruments and experimental devices. Among them, the Secondary Ion Mass Spectrometers (SIMS) Cameca IMS1280-HR equipped with the new Hyperion oxygen sources will be at the heart of the project allowing the in-situ analysis of hydrous and nominally anhydrous minerals.
For the most hydrated samples, we will use a method based on in-situ measurements of the C/H and D/H ratios by SIMS to estimate the isotopic composition of water-bearing minerals. This method, recently developed by HYDRaTE's PI, allows for the first time the D/H ratios of hydrous chondritic minerals to be determined without hindrance from hydrogen in adjacent organic materials. Coupled with ion imaging for measuring the D/H composition of organic particles, this will permit an exhaustive assessment of the origin of volatile-rich molecules in primitive solar system materials.
We will investigate the distribution of hydrogen in the major high-temperature components of chondrites, the chondrules, via laboratory experiments and analytical measurements. We will build an experimental device to melt and crystallize chondrule analogues under conditions close to those estimated for the protoplanetary disk (low total pressure, low oxygen fugacity) and high partial pressures of H2 and/or H2O. Through these experiments, we will study the consequences of the presence of hydrogen-rich gases on chondrule formation and provide for the first time thermodynamical data on hydrogen partitioning and isotopic fractionation under conditions close to those estimated for the protoplanetary disk. These experimental results will be compared to the hydrogen compositions of natural samples. Indeed, a major achievement of HYDRaTE will be to quantify the hydrogen abundance and isotopic composition of chondrule silicates, with particular focus on enstatite chondrites, the best candidate for the Earth's building blocks, and to estimate the contribution of the different categories of chondrites to the H budget of Earth and the other terrestrial planets.