The micrometeorite flux at Dome C (Antarctica), monitoring the accretion of extraterrestrial dust on Earth

The annual flux of extraterrestrial material on Earth is largely dominated by sub-millimetre particles. The mass distribution and absolute value of this cosmic dust flux at the Earth's surface is however still uncertain due to the difficulty in monitoring both the collection efficiency and the exposure parameter (i.e. the area-time product in m(2).yr). In this paper, we present results from micrometeorite collections originating from the vicinity of the CONCORDIA Station located at Dome C (Antarctica), where we performed several independent melts of large volumes of ultra-clean snow. The regular precipitation rate and the exceptional cleanliness of the snow from central Antarctica allow a unique control on both the exposure parameter and the collection efficiency. A total of 1280 unmelted micrometeorites (uMMs) and 808 cosmic spherules (CSs) with diameters ranging from 30 to 350 mu m were identified. Within that size range, we measured mass fluxes of 3.0 g.m(-2).yr(-1) for uMMs and 5.6 mu g.m(-2).yr(-1) for CSs. Extrapolated to the global flux of particles in the 12-700 um diameter range, the mass flux of dust at Earth's surface is 5, 200 +/- (1500)(1200) tons.yr(-1) (1,600 +/- 500 and 3, 600 +/-(1000)(700) tons.yr(-1) of uMMs and CSs, respectively). We indicate the statistical uncertainties expected for collections with exposure parameters in the range of 0.1 up to 10(5)m(2).yr. In addition, we estimated the flux of altered and unaltered carbon carried by heated and un-heated particles at Earth's surface. The mass distributions of CSs and uMMs larger than 100 mu m are fairly well reproduced by the CABMOD-ZoDy model that includes melting and evaporation during atmospheric entry of the interplanetary dust flux. These numerical simulations suggest that most of the uMMs and CSs originate from Jupiter family comets and a minor part from the main asteroid belt. The total dust mass input before atmospheric entry is estimated at 15,000 tons.yr(-1). The existing discrepancy between the flux data and the model for uMMs below 100 mu m suggests that small fragile uMMs may evade present day collections, and/or that the amount of small interplanetary particles at 1 AU may be smaller than expected. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

The study reveals that the total dust mass input at Earth's surface is estimated to be 5,200 tons per year, mainly originating from Jupiter family comets and a minor part from the main asteroid belt.