Date/heure
Date(s) - 28 mars 2024
16 h 00 min - 17 h 00 min
Catégories
Flux of interplanetary dust particles and micrometeorites at Dome C (Antarctica): a fresh look with helium isotopes, by G. Fénisse (CRPG).
Cosmic dust including interplanetary dust particles (IDPs) and micrometeorites (MMs) range in size from ≥ 1 µm to ≅ 1 mm and represent the dominant source of extraterrestrial (ET) material entering Earth’s atmosphere, with few thousand tons/year on Earth. However, dust accretion rates, volatile contents and atmospheric heating processes are still underconstrained. In particular, the flux of ET particles smaller than 50 microns remains uncertain and strongly differs from that expected from numerical simulation (CABMOD-ZoDy, Carrillo-Sánchez et al., 2020). Moreover, these IDPs bring to Earth 3HeET that is subsequently mixed in sediments and represent a good sedimentological proxy, to determine sedimentation rates and anomalous spikes of ET contributions. Measurements of MMs flux were traditionally done by particles counting, but this method is challenging, time consuming and non applicable for the smallest (IDPs) particles.
In this study, we measure the helium-3 and helium-4 concentrations in cosmic dust concentrated in ultra-clean melted snow from the CONCORDIA station located at Dome C (Antarctica). We then use an exhaustive literature data compilation of He and Ne isotopic concentrations in cosmic dust particles to establish a robust 4He content-cosmic dust size relationship. From these data, we estimate an 3HeET annual flux of 1.04 ± 0.01 pico cc STP/cm²/ka and derive the ET and Terrestrial helium relative contributions for each granulometric fraction. Both information appear consistent with previous studies. Using measured 4He abundances of IDPs/MMs from the CONCORDIA station and 4He-mass linear regression of our previous database, the total dust mass input is 8.1 ± 0.3 thousand tons/year, an intermediate value between direct counting method and CABMOD-ZoDy simulations.