On the size and velocity distribution of cosmic dust particles entering the atmosphere

Abstract

The size and velocity distribution of cosmic dust particles entering the Earth's atmosphere is uncertain. Here we show that the relative concentrations of metal atoms in the upper mesosphere, and the surface accretion rate of cosmic spherules, provide sensitive probes of this distribution. Three cosmic dust models are selected as case studies: two are astronomical models, the first constrained by infrared observations of the Zodiacal Dust Cloud and the second by radar observations of meteor head echoes; the third model is based on measurements made with a spaceborne dust detector. For each model, a Monte Carlo sampling method combined with a chemical ablation model is used to predict the ablation rates of Na, K, Fe, Mg, and Ca above 60 km and cosmic spherule production rate. It appears that a significant fraction of the cosmic dust consists of small (<5 µg) and slow (<15 km s −1 ) particles.

Novel Experimental Simulations of the Atmospheric Injection of Meteoric Metals

“…On the other hand, partially molten MMs show multiple beads. The expected atmospheric entry scenario for the Fe-bearing metal-sulfide phase in IDPs should be intermediate between curves labelled "200" and "1", because only a fraction of incoming IDPs form cosmic spherules (Carrillo-Sánchez, et al 2015). A Fe metallic-sulfide phase will be implemented in the follow-up development of CABMOD and will be reported elsewhere.…”

“…The mass and velocity distribution of IDPs derived from High Performance Large Aperture (HPLA) radar observations at Arecibo (Janches, et al 2006) are very different from those inferred from orbital impact detection by the Long Duration Exposure Facility (LDEF) (Love & Brownlee 1993) and Infrared Astronomical Satellite (IRAS) observations of the Zodiacal Cloud (Nesvorný et al 2010), which leads to disparate fluxes of gas-phase meteoric metals and MMs (Carrillo-Sánchez, et al 2015;Plane 2012). This difference has been interpreted as a result of the bias of radars towards fast/large meteoroids (Janches et al 2014;Janches et al 2015).…”

“…This difference has been interpreted as a result of the bias of radars towards fast/large meteoroids (Janches et al 2014;Janches et al 2015). The best match of metal layer density ratios and the fluxes of MMs and spherules is obtained when CABMOD is combined with an astronomical dust model constrained by Zodiacal Cloud observations, although some discrepancies between model and observations persist (Carrillo-Sánchez, et al 2015).…”

“…This model has therefore been at the core of recent efforts to quantify the input of IDPs into the terrestrial atmosphere by reconciling observations ranging from MM samples collected at the surface to astronomical observations of the Zodiacal infrared emission (Carrillo-Sánchez, et al 2015;Plane 2012). CABMOD has been used previously in combination with mass and velocity distribution of IDPs derived from different observations in order to explain atmospheric metal relative abundances and the flux of micrometeorites and spherules collected in the polar icecaps (Carrillo-Sánchez, et al 2015).…”

Comparison of global datasets of sodium densities in the mesosphere and lower thermosphere from GOMOS, SCIAMACHY and OSIRIS measurements and WACCM model simulations from 2008 to 2012

“…This highly varying input, however, does not significantly increase the densities of the metal layers (see, e.g., Correira et al, 2010). The meteoroids that enter the Earth's atmosphere have geocentric speeds between 11.5 and 72.5 km s −1 and a mass distribution between 10 −13 and 10 −4 kg, with current estimations from Nesvorný et al (2010), Love and Brownlee (1993) and Fentzke and Janches (2008) showing a maximum on the order of magnitude of 10 −9 to 10 −7 kg (see Carillo-Sánchez et al (2015) for a comparison and detailed discussion on this issue). The ablation process (see, e.g., McNeil et al, 1998;Vondrak et al (2008)) takes place at altitudes between 80 and 125 km, resulting in the deposition of metallic atoms such as sodium (Na), magnesium (Mg), iron (Fe), potassium (K), calcium (Ca), nickel (Ni) and others in the MLT.…”