A Primitive solar Atmosphere around The young Earth?

Project Information

APATE

Grant agreement ID: 101096688

DOI

10.3030/101096688

EC signature date 2 May 2023

Start date 1 September 2023

End date 31 August 2028

Funded under

• European Research Council (ERC)

Total cost

€ 2 784 505,00

EU contribution

€ 2 784 505,00

Coordinated by

UNIVERSITE D'ORLEANS
France

Periodic Reporting for period 1 - APATE (A Primitive solar Atmosphere around The young Earth?)

Reporting period: 2023-09-01 to 2026-02-28

Summary of the context and overall objectives of the project

The existence of an atmosphere enriched in H and He around the Earth as it formed has often been proposed. One hypothesis suggests that it could have been captured from the gas present in the proto-planetary disk, before its evaporation. Subsequently, a secondary atmosphere would have been degassed or brought in by a late veneer of chondritic/cometary material. Although this model is regularly evoked using giant planets for comparison, there is no geological proof for its existence, except possibly for the neon in the Earth's mantle. While the model has a flaw (mainly relating to chronology, as the gas from the disk is lost in <6 My while the Earth formed over a period of more than 30My), the solar-type neon in the Earth's mantle is an argument for the existence of such a captured atmosphere, which partially dissolved into a magma ocean. A second scenario for a primordial H2/He-rich atmosphere is the degassing of a mantle that contained implanted solar wind. The APATE project aims to study the isotopic composition of neon in the Earth's mantle in order to determine if this composition is the same
as that of the nebula or the solar wind material. We will investigate the degassing processes of magmas experimentally and numerically in order to study the isotopic fractionation that occurs during bubble formation and to determine whether the measured neon isotopic composition can provide an accurate composition for the original mantle. The project aims to calculate the amount of neon that can be incorporated into a magma ocean by establishing the atmospheric pressure of the captured atmosphere and by studying the dynamics of the magma ocean. We will also explore the hypothesis involving solar wind irradiation. Using simulations of irradiation, we will identify those conditions under which this model is realistic and its implications for the Earth’s (isotopic/chemical) composition. The origin of light solar volatiles will then be explored by the APATE project.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

A significant milestone was the acquisition of the new mass spectrometer (Noblesse 5F5M), essential for advancing our research. While the project officially began on September 1, 2023, the instrument was delivered on June 13, 2024—a delay of nearly nine months. Following delivery, the initial weeks focused on rigorous testing and standard analyses as part of Work Package WP0 (Installation).
In July 2024, we conducted a two-week sampling mission in Iceland, collecting fresh glass samples for WP1 (“Neon in the Mantle”) and to support Romain Sauvalle’s PhD research. This enabled us to pioneer the Bubble-by-Bubble analysis technique, combining an ablation laser with the new spectrometer, alongside step-crushing experiments. The results, now in press at Earth and Planetary Science Letters (Sauvalle et al., 2025), mark a major methodological advancement.
Concurrently, we advanced WP2 (“Magmatic Processes”) through experimental studies on neon isotopic fractionation during magma degassing. Led by newly recruited research engineer Elena Nunez and in collaboration with Dr. Bruno Scaillet, our findings confirmed significant fractionation effects (Nunez et al., 2025). Additionally, the post-doc Jehiel Nteme, a molecular dynamics specialist, further validated these observations through computational modeling. These results were presented at the Goldschmidt Conference in Prague (Nteme et al. 2025).
For WP3 (“Capture of Atmosphere”), we investigated neon solubility in synthetic melts with variable MgO content, simulating conditions of the primordial magma ocean. Spearheaded by the post doc Carolina Cardoso-Dantes and supported by Dr. Scaillet, our experiments revealed that higher MgO content reduces neon solubility, challenging previous estimates of solar neon dissolution. These findings are now published in Cardoso et al. (2025).]

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The most significant advancements in the project involves the application of the bubble-by-bubble technique—specifically laser ablation on basaltic samples—to demonstrate that the mantle source of the Icelandic hotspot exhibits a neon isotopic composition remarkably close to that of implanted solar wind (Sauvalle et al., 2025). This method also revealed that neon isotopes undergo fractionation during vesicle formation, indicating that the isotopic ratios measured in natural samples may be fractionated in certain geological contexts, such as during rapid magma migration toward the surface (Núñez et al. 2025). Additionally, our work has shown that neon solubility in mafic magmas (those rich in MgO) is significantly lower than in basalt, challenging previous estimates and suggesting that the dissolution of neon from a dense solar atmosphere into a magma ocean is more complex than initially thought (Cardoso et al., 2025). Complementing these findings, molecular dynamics simulations of neon solubility and diffusion in basaltic magma further confirmed that the two neon isotopes fractionate during vesicle formation, with an isotopic fractionation factor α in (m₁/m2)ᵃ of approximately 0.3—substantially lower than the theoretically predicted value of 0.5 (the square root of the mass ratio) (Nteme et al., 2025). These results collectively enhance our understanding of neon behaviour in geological processes and its implications for planetary formation.]