Lunch talk on Mar. 30, 2026

Carbon depletion problem of the rocky bodies in the inner Solar System

Speaker: Tamami Okamoto (TDLI)

Venue: SWIFAR Building 2111

Time: 12:45 PM, Monday, Mar. 30, 2026

Abstract: 

The formation history of the Solar System remains unclear. However, the chemical composition of planets and small bodies may provide clues, as it reflects the motion of solids within the protoplanetary disk. In this talk, I focus on the carbon depletion problem of Earth and other rocky bodies, presenting simulation results that aim to replicate their observed carbon abundance by tracking the motion of solids and the chemical reactions they experienced in the disk. Earth and other inner Solar System rocky bodies are significantly depleted in carbon compared to comets and interstellar medium (ISM) dust. Observations show that over half of the carbonaceous solids in the ISM and comets are refractory enough to survive near the Earth’s orbits. To explain this carbon depletion, refractory carbons must be destroyed. To investigate the conditions required for such severe depletion, we track the motion of carbonaceous solids in the disk and calculate their mass loss due to photo-degradation from solar far-ultraviolet radiation and thermal decomposition. Our findings indicate that a significant drop in carbon abundance occurs inside the snow line when: i) silicate particles are much less sticky than icy particles, causing a rapid decline in the flux of icy pebbles while silicates remain inside the snow line, and ii) the disk’s upper layer is more turbulent, lifting more silicate particles into UV-exposed regions. I will also discuss the model’s caveats and compare our results with observational data.