The extraterrestrial dust accretion rate on Earth at Dome C, Antarctica: a fresh look with 3He

Abstract

Interplanetary dust particles (IDPs) and micrometeorites (MMs), from 1 µm to 5 mm, are the primary source of extraterrestrial (ET) material currently accreted on Earth. The flux of ET particles smaller than ∼50 µm is typically determined through optical counting, but it remains uncertain and may deviate from predictions made by numerical simulations. The volatile element content carried by this flux is still not well-constrained and is influenced by the potential effects of atmospheric heating.

We developed a clean, pressurized system to extract cosmic dust from ∼38 kg of clean snow collected near the Concordia station (Dome C, Antarctica). We measured helium isotope concentrations in various granulometric fractions (> 62 µm, 25–62 µm, 5–25 µm and < 5 µm). The inferred global ³He_ET annual flux is (1.25±0.03) × 10⁻¹² ccSTP·cm⁻²·ka⁻¹ (weighted mean±1SD), consistent with previous ³He_ET flux estimates from marine sediments and polar samples. Our data shows that the majority of the ³He_ET flux (70 %) is carried by particles in the 5–25 µm size range, with 20 % attributed to the 25–62 µm fraction. Using an empirical relationship between ³He_ET concentrations and cosmic particle mass, we convert these fluxes into a global ET mass flux for particle diameters < 100 µm of (3.5±0.5) kilotons·a⁻¹ (weighted mean±1SD). This result is about 3 times higher than collection estimates from (Rojas et al., 2021) and aligns with CABMOD-ZoDy modeling, after atmospheric entry (Carrillo-Sánchez et al., 2020). This ³He_ET method is suited for detecting particles smaller than 100 µm, while collection results are more relevant for larger fractions.