Planetary science: Deciphering the nature of Earth’s building blocks
Nature
2017년1월26일

Insights into the composition of the meteoritic material added to the Earth during its formation are provided in two papers published in this week’s Nature. The Earth formed by the accretion of Moon-sized to Mars-sized bodies from various sources, but determining the isotopic composition of these meteoritic building blocks has remained challenging.
Nicolas Dauphas shows that the isotopic nature of the Earth’s building blocks over time can be deciphered using signatures in the mantle of elements with differing affinities for metal. Lithophile (‘stone-loving’) elements, such as oxygen and calcium, tend to remain in the rocky mantle, whereas siderophile (‘iron-loving’) elements tend to move into the underlying core. The analyses suggest that the meteorites accreted by the Earth have not changed much over time and always contained a large proportion of material of isotopic composition similar to that of enstatite meteorites. This finding could also help to explain the similar isotopic compositions of the Earth and Theia, the hypothetical giant Moon-forming impactor.
In a second paper, Mario Fischer-Godde and Thorsten Kleine report that the Earth seems to have obtained its volatiles, including water, throughout its growth, rather than late in the Earth’s history through the accretion of chondrites (a type of stony meteorite) or comets. Siderophile elements, such as gold, iron and ruthenium, that are now present in the Earth’s mantle are thought to result from the ‘late veneer’ of material that accumulated after the Moon-forming impact. This study finds that all chondrites have ruthenium isotope compositions that are more different from that of the Earth’s mantle the further from the Sun they formed. This suggests that the late veneer was not, in fact, the primary source of volatiles and water on the Earth, and instead had a composition similar to that of enstatite meteorites.
doi: 10.1038/nature20830
리서치 하이라이트
-
3월4일
Environment: Reservoirs account for more than half of water storage variabilityNature
-
3월2일
Evolution: Neanderthals may have heard just like usNature Ecology & Evolution
-
3월2일
Geoscience: Earth’s atmosphere may return to low-levels of oxygen in one billion yearsNature Geoscience
-
2월26일
Environment: Shifting from small to medium plastic bottles could reduce PET wasteScientific Reports
-
2월24일
Environment: European forests more vulnerable to multiple threats as climate warmsNature Communications
-
2월11일
Environment: Global CFC-11 emissions in declineNature