[S-IT21] Understanding the first 150 million years of the solar system

[SIT21-06] Composition, origin, and evolution of the Earth and its energy budget

*William F McDonough¹ (1.WPI-AIMEC, Tohoku University, Sendai, Miyagi 980-8578, Japan)

キーワード：geoneutrino, protoplanetary disk, Earth's composition, Mars

The Sun's oxygen isotopic composition, which is the third most abundant element in the solar system, is distinct from that of Earth, Mars, and Moon. Oxygen is the most abundant element in these rocky bodies. The rocky planets grew rapidly (<10 million years) from large populations of planetesimals, most of which were differentiated (i.e., had a core and mantle) before being accreted. Planetary growth in the early stages protoplanetary disk evolution was rapid and was only partially recorded by the meteoritic record. Most chondrites in our collection formed after the first couple of millions of years of solar system evolution, in the middle to later stages of the protoplanetary disk evolution. The consequence of not having a definitive meteoritic record from early differentiated planetesimals, for example the silicates associated with the iron meteorites, imposes a bias on our models for the rocky planets.

Earth and Mars are enriched in refractory elements about 1.9 times that of CI chondrite. Earth is more volatile-depleted and less oxidized than Mars. The composition of the Earth, its current planform of mantle convection, and the amount of radiogenic power that drives its engine remain a controversial topic. Earth’s dynamics are driven by primordial and radiogenic heat sources. Measurement of the Earth's geoneutrino flux defines its radiogenic power and restricts its bulk composition. Using the latest data from the KamLAND and Borexino geoneutrino experiments affirms that the Earth has $\leq$20 TW of radiogenic power and sets the proportions of refractory lithophile elements at 2.5 to 2.7 times those in carbonaceous chondrites in CI.