2024-01-04 カリフォルニア工科大学(Caltech)
◆これまでの理論では水の存在は疑わしく、後に追加されたとされていたが、この研究により初期の太陽系形成において水が重要な役割を果たした可能性が浮かび上がった。
＜関連情報＞
- https://www.caltech.edu/about/news/meteorite-analysis-shows-earths-building-blocks-contained-water
- https://www.nature.com/articles/s41550-023-02172-w
太陽系内最初期の惑星系準惑星の水の降着が雪の境界線を超える Accretion of the earliest inner Solar System planetesimals beyond the water snowline
Damanveer S. Grewal,Nicole X. Nie,Bidong Zhang,Andre Izidoro & Paul D. Asimow
Nature Astronomy Published:09 January 2024
DOI:https://doi.org/10.1038/s41550-023-02172-w
Abstract
How and where the first generation of inner Solar System planetesimals formed remains poorly understood. Potential formation regions are the silicate condensation line and water snowline of the solar protoplanetary disk. Whether the chemical compositions of these planetesimals align with accretion at the silicate condensation line (water-free and reduced) or water snowline (water-bearing and oxidized) is, however, unknown. Here we use the Fe/Ni and Fe/Co ratios of magmatic iron meteorites to quantify the oxidation states of the earliest planetesimals associated with non-carbonaceous (NC) and carbonaceous (CC) reservoirs, representing the inner and outer Solar System, respectively. Our results show that the earliest NC planetesimals contained substantial amounts of oxidized Fe in their mantles (3–19 wt% FeO). In turn, we argue that this required the accretion of water-bearing materials into these NC planetesimals. The presence of substantial quantities of moderately and highly volatile elements in their parent cores is also inconsistent with their accretion at the silicate condensation line and favours, instead, their formation at or beyond the water snowline. Similar oxidation states in the early formed parent bodies of NC iron meteorites and those of NC achondrites and chondrites with diverse accretion ages suggest that the formation of oxidized planetesimals from water-bearing materials was widespread in the early history of the inner Solar System.
