Micrometeorite flux on Earth during the last ~50,000 years

Abstract

AbstractFlux of micrometeorites is estimated by using cosmic spherule counts from a seafloor area of 2.50 m2 from the Indian Ocean. The spherules are recovered from sediment samples in close‐spaced locations from the Indian Ocean after sieving 293 kg of sediment. The terrestrial age of the spherules has a range of 0–~50,000 years. The spherules have a size range of 57–750 µm (average size 265 ± 92 µm). The diameter of the spherules increases from scoriaceous‐barred‐cryptocrystalline‐glassy types. The time‐averaged flux of the spherules is 160 t/yr, a sizeable mass (>60%) resides in the >300 µm fraction; the slope of distribution is similar to that of Deep‐Sea Spherules but significantly different from other collections which have lower average diameters. It is observed here, a significant population of cosmic dust resides in the larger sizes which can be recovered by sampling large areas in time and space. The spherule textures are similar to that of unbiased collections from the polar regions, indicating that the textural types of cosmic dust that have been raining on the Earth during the last 50 kyr have been constant regardless of size. Major element chemistry of a majority of the spherules show elemental ratios that are close to a CM or CI chondritic parent body; a single spherule (0.2% of the population) suggests an achondritic parent body. Unbiased collections spanning large areas temporally and spatially enlarge the inventory of the Earth‐crossing meteoroid complex and provide valuable inputs for models on cosmic dust accretion.