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

Abstract

[1] Flux of micrometeorites is estimated by using cosmic spherule counts from a seafloor area of 2.50 m 2 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.

Ablation and Chemical Alteration of Cosmic Dust Particles During Entry Into the Earth’s Atmosphere

“…3-31;Lodders & Fegley 1998). The major elemental composition of micrometeorites conforms to a CI composition, as suggested by various studies (e.g., Brownlee et al 1997;Taylor et al 2000;Prasad et al 2013). The majority of the dust producers in the asteroid belt are bodies that have low tensile strength and that can fragment into smaller particles during collisions; CI chondrite fits this category very well.…”

“…Although efforts have been made to learn the exact contributions from each of these sources, such efforts are nevertheless hampered by large levels of uncertainties (e.g., Plane 2012). Micrometeorites are the largest contributors of extra-terrestrial material; this material is recovered from the Earthʼs surface using different collection techniques that target the stratosphere, Antarctica, and deep-sea sediments (Love & Brownlee 1993;Taylor et al 1998;Peucker-Ehrenbrink & Ravizza 2000;Plane 2012;Prasad et al 2013). The micrometeorites found on the Earthʼs surface have distinct chemical compositions that show similarities and differences with respect to the precursors they originate from; however, in general, a large number of micrometeorites are related to carbonaceous chondrites (e.g., Kurat et al 1994;Brownlee et al 1997;Taylor et al 2000Taylor et al , 2012Yada et al 2005;Rudraswami et al 2011Rudraswami et al , 2012Rudraswami et al , 2014Rudraswami et al , 2015aRudraswami et al , 2015bRudraswami et al , 2016a.…”

“…Numerical calculations will also be a useful parameter for providing estimates of the flux, which has so far been assessed with multiple values (Taylor et al 1998;Yada et al 2004;Plane 2012;Prasad et al 2013). We use the Chemical ABlation MODel (CABMOD; Vondrak et al 2008) to derive the ablation rate profiles of the most abundant elements as a function of the altitude for each meteoroid with a given mass, velocity, and entry angle after it enters the atmosphere.…”

Relict Olivines in Micrometeorites: Precursors and Interactions in the Earth’s Atmosphere

“…The Antarctica micrometeorites (AMM) were collected from the South Pole Water Well (SPWW), which has a diameter of ∼24 m at a depth of ∼100 m below the snow surface, with a total water volume of ∼5000 m 3 (Taylor et al 1998(Taylor et al , 2000. The cosmic spherules from deep sea sediments (CS-DSS) were collected at water depths of ∼5200 m using an Okean grab sampler with a seafloor penetration depth of ∼15 cm (Rudraswami et al 2012(Rudraswami et al , 2014(Rudraswami et al , 2015aPrasad et al 2013). The AMM and CS-DSS have been dated at ∼900 years BP and 0-50,000 years BP, respectively (Taylor et al 1998(Taylor et al , 2007Prasad et al 2013).…”

“…The forsteritic olivine of micrometeorites collected from Antarctica and deep sea sediments has been studied previously to discern the nature of the precursor and its behavior during atmospheric entry (Taylor et al 1998(Taylor et al , 2000Prasad et al 2013Prasad et al , 2015. However, in the present study, we will use the Chemical Ablation Model (CABMOD, Vondrak et al 2008) to understand the ablation of major and minor elements and the thermal history that a meteoroid of specified mass, velocity and entry angle undergoes during flight through the atmosphere before landing on the Earth's surface as a micrometeorite.…”