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 will permit an exhaustive assessment of the origin of volatile-rich molecules in primitive solar system materials.

We are investigating 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 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.

- We have determine 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 these distribution in the disk at the time and place of the chondrite parent formation. This work have been published in Earth and Planetary Science Letters in May 2021.

- Enstatite chondrites are considered as good analogues to the Earth's building blocks. One of the first work of the project has been to determine the water concentration and isotopic composition of a series of enstatite chondrites. The coupling of two analytical techniques, the conventional mass spectrometry and the secondary ion mass spectrometry (SIMS), allowed them to precisely measure the low water contents of enstatite chondrites without being biased by terrestrial contamination. The results demonstrate that the enstatite chondrites contain enough water to deliver at the minimum 3 times the total amount of water of the Earth’s oceans. The hydrogen isotopic composition of enstatite chondrites was found to be similar to the one of the water stored in the terrestrial mantle. We also show that a large amount of the atmospheric nitrogen (the most abundant component of the Earth’s atmosphere) could also come from the enstatite chondrites. These major results have been reported in a paper published in Science in August 2020.

Further analyses are on-going to precise: (1) the nature of the H-bearing phases in enstatite chondrites, (2) the isotopic composition of H in the different H-bearing phases, and (3) the abundance and composition of other volatile elements such as C, N or halogens that could have a common origin with hydrogen. The goal of this work is to better understand the formation environnements of chondrules and the volatile element distribution in the protoplanetary disk at the time of 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.