Flux of small interplanetary dust particles at Dome C (Antarctica):A fresh look with helium isotopes

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 5,200 tons/year [4].However, dust accretion rates, volatile contents and histories of atmospheric heating are still debated [5].In particular, the flux of ET particles smaller than 50 microns remains highly uncertain and strongly differs from that expected from numerical simulation by CABMOD-ZoDy [1].Moreover, these IDPs bring to Earth 3 He ET that is subsequently mixed in sediments and can provide a good proxy for geochemical reconstructions (e.g., sedimentation rates and detection of anomalous ET spike).Traditional particle counting techniques to determine ET material fluxes remain challenging and affected by large uncertainties [4].Here, we measured the helium-3 and helium-4 concentrations in cosmic dust concentrated in ultra-clean snow from the Concordia station located at Dome C (Antarctica) [2].After several steps of snow filtration down to 0.47 μm using a dedicated pressurized system, filters concentrating cosmic dust particles were observed under a microscope and the volume and mass of particles were estimated.The filters containing the recovered particles were then heated using an induction furnace and analyzed for their helium isotopic abundances using a Thermo Scientific SFT mass spectrometer.From these data, we attempt to better estimate the 3 He ET annual flux and the mass of dust particles accreted to Earth.After compiling the available literature data, we observe that high helium and neon concentrations are correlated with the surface-to-volume ratios of particles, confirming that the implantation of solar wind ions in space [3] is likely the main source of light noble gases in IDPs and MMs.