Meteoric CaO and carbon smoke particles collected in the upper stratosphere from an unanticipated source (original) (raw)
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Meteoric smoke production in the atmosphere
Geophysical Research Letters, 2000
Nanometer-sized smoke particles produced during ablation of incoming micrometeorites influence the ion chemistry in the 80-120km region and are believed to play an important role in the nucleation of mesospheric ice particles. We present a new model of cosmic dust ablation and smoke production in the Earth's atmosphere using realistic size and velocity distributions of the incoming dust particles. We show that, while the seasonal changes in our atmosphere can be safely neglected, the shape of micro-meteoroids strongly affects their ablation.
Meteoritic dust from the atmospheric disintegration of a large meteoroid
Nature, 2005
Much of the mass of most meteoroids entering the Earth's atmosphere is consumed in the process of ablation. Larger meteoroids (> 10 cm), which in some cases reach the ground as meteorites, typically have survival fractions near 1-25 per cent of their initial mass. The fate of the remaining ablated material is unclear, but theory suggests that much of it should recondense through coagulation as nanometre-sized particles. No direct measurements of such meteoric 'smoke' have hitherto been made. Here we report the disintegration of one of the largest meteoroids to have entered the Earth's atmosphere during the past decade, and show that the dominant contribution to the mass of the residual atmospheric aerosol was in the form of micrometre-sized particles. This result is contrary to the usual view that most of the material in large meteoroids is efficiently converted to particles of much smaller size through ablation. Assuming that our observations are of a typical event, we suggest that large meteoroids provide the dominant source of micrometre-sized meteoritic dust at the Earth's surface over long timescales.
The MAGIC meteoric smoke particle sampler
Journal of Atmospheric and Solar-Terrestrial Physics, 2014
Between a few tons to several hundred tons of meteoric material enters the 39 Earth s atmosphere each day, and most of this material is ablated and vaporized 40 in the 70 to 120 km altitude region. The subsequent chemical conversion, re-41 condensation and coagulation of this evaporated material are thought to form 42 nanometre sized meteoric smoke particles (MSPs). These smoke particles are 43 then subject to further coagulation, sedimentation and global transport by the 44 mesospheric circulation. MSPs have been proposed as a key player in the 45 formation and evolution of ice particle layers around the mesopause region, i.e. 46 noctilucent clouds (NLC) and polar mesosphere summer echoes (PMSE). MSPs 47 have also been implicated in mesospheric heterogeneous chemistry to influence 48 the mesospheric odd oxygen/odd hydrogen (Ox/HOx) chemistry, to play an 49 important role in the mesospheric charge balance, and to be a significant 50 component of stratospheric aerosol and enhance the depletion of O3. 51 Despite their apparent importance, little is known about the properties of MSPs 52 and none of the hypotheses can be verified without direct evidence of the 53 existence, altitude and size distribution, shape and elemental composition. The 54 aim of the MAGIC project (Mesospheric Aerosol Genesis, Interaction and 55 Composition) was to develop an instrument and analysis techniques to sample 56 for the first time MSPs in the mesosphere and return them to the ground for 57 detailed analysis in the laboratory. MAGIC meteoric smoke particle samplers 58 have been flown on several sounding rocket payloads between 2005 and 2011. 59 Several of these flights concerned non-summer mesosphere conditions when 60 pure MSP populations can be expected. Other flights concerned high latitude 61 summer conditions when MSPs are expected to be contained in ice particles in 62 the upper mesosphere. In this paper we present the MAGIC project and describe 63 the MAGIC MSP sampler, the measurement procedure and laboratory analysis. 64 We also present the attempts to retrieve MSPs from these flights, the challenges 65 inherent to the sampling of nanometre sized particles and the subsequent 66 analysis of the sampled material, and thoughts for the future. Despite substantial 67 experimental efforts, the MAGIC project has so far failed to provide conclusive 68 results. While particles with elemental composition similar to what is to be 69 expected from MSPs have been found, the analysis has been compromised by 70 challenges with different types of contamination and uncertainties in the sticking 71 efficiency of the particles on the sampling surfaces. 72 73 amount of this incoming material is a subject of controversy (Plane, 2012) with 76 estimates ranging from a few tons to several hundred tons per day (Hughes, 77
Distribution of meteoric smoke – sensitivity to microphysical properties and atmospheric conditions
Atmospheric Chemistry and Physics, 2006
Meteoroids entering the Earth's atmosphere experience strong deceleration and ablate, whereupon the resulting material is believed to re-condense to nanometre-size "smoke particles". These particles are thought to be of great importance for many middle atmosphere phenomena, such as noctilucent clouds, polar mesospheric summer echoes, metal layers, and heterogeneous chemistry. The properties and distribution of meteoric smoke depend on poorly known or highly variable factors such as the amount, composition and velocity of incoming meteoric material, the efficiency of coagulation, and the state and circulation of the atmosphere. This work uses a one-dimensional microphysical model to investigate the sensitivities of meteoric smoke properties to these poorly known or highly variable factors. The resulting uncertainty or variability of meteoric smoke quantities such as number density, mass density, and size distribution are determined. It is found that the two most important factors are the efficiency of the coagulation and background vertical wind. The seasonal variation of the vertical wind in the mesosphere implies strong global and temporal variations in the meteoric smoke distribution. This contrasts the simplistic picture of a homogeneous global meteoric smoke layer, which is currently assumed in many studies of middle atmospheric phenomena. In particular, our results suggest a very low number of nanometre-sized smoke particles at the summer mesopause where they are thought to serve as condensation nuclei for noctilucent clouds.
Carbon Star Dust from Meteorites
Symposium - International Astronomical Union, 2000
Inside carbonaceous chondrite meteorites are tiny dust particles which, when heated, release noble gases with an isotopic composition different from what is found anywhere else in the solar system. For this reason it is believed that these grains are (inter)stellar dust which survived the collapse of the interstellar cloud that became the solar system. We will describe here why we believe that the most abundant of these grains, micro-diamonds, were formed in the atmospheres of carbon stars, and explain how this theory can be tested observationally.
Journal of Geophysical Research: Atmospheres, 2017
The accumulation rate of meteoric smoke particles (MSPs) in ice cores-determined from the trace elements Ir and Pt, and superparamagnetic Fe particles-is significantly higher than expected from the measured vertical fluxes of Na and Fe atoms in the upper mesosphere and the surface deposition of cosmic spherules. The Whole Atmosphere Community Climate Model with the Community Aerosol and Radiation Model for Atmospheres has been used to simulate MSP production, transport, and deposition, using a global MSP input of 7.9 t d À1 based on these other measurements. The modeled MSP deposition rates are smaller than the measurements by factors of~32 in Greenland and~12 in Antarctica, even after reanalysis of the Ir/Pt ice core data with inclusion of a volcanic source. Variations of the model deposition scheme and use of the United Kingdom Chemistry and Aerosols model do not improve the agreement. Direct removal of MSP-nucleated polar stratospheric cloud particles to the surface gives much better agreement, but would result in an unfeasibly high rate of nitrate deposition. The unablated fraction of cosmic dust (~35 t d À1) would provide sufficient Ir and Pt to account for the Antarctic measurements, but the relatively small flux of these large (>3 μm) particles would lead to greater variability in the ice core measurements than is observed, although this would be partly offset if significant fragmentation of cosmic dust particles occurred during atmospheric entry. Future directions to resolve these discrepancies between models and measurements are also discussed. Plain Language Summary About 40 t of space dust enters the atmosphere every day. Around 20% of the dust vaporizes during entry because the particles enter at speeds of over 40,000 kph. The resulting metal vapors (principally Fe, Mg, and Si) then oxidize and condense into tiny particles known as meteoric smoke, around 1 nm in radius. This study examines where the meteoric smoke is deposited at the Earth's surface. The smoke has been detected in polar ice cores, with a much higher deposition rate than expected from measurements in the upper atmosphere. A global circulation model was therefore used to analyze how the smoke is transported from around 80 km altitude and deposited in Greenland and Antarctica, mainly by snow. The model cannot satisfactorily account for either the absolute rate of deposition or the ratio of the deposition rates in the polar regions. A variety of explanations to account for this discrepancy are then explored, including a volcanic artifact in the ice cores, fragmentation of meteoroids, and a temporal change in the cosmic dust input.
The chemistry of carbon dust formation
… of the 191st …, 1999
We shall review the various types of , chemistry involved in the formation of carbonaceous material present in carbon-rich AGB stars, mainly amorphous carbon, silicon carbide and other metal carbides discovered in pre-solar stardust extracted from meteorites. The chemistry is discussed in the context of laboratory experiments and their application to circumstellar AGB winds. Emphasis is put on polycyclic aromatic hydrocarbons (PAHs), titanium carbide clusters and silicon carbide grains. Attempt to explain the condensation sequences derived from the study of pre-solar grains of meteoretical origin is made on the basis of physio-chemical models which describe the periodically shocked gas close to the photosphere of AGB stars.
Global and temporal distribution of meteoric smoke: A two-dimensional simulation study
Journal of Geophysical Research, 2008
1] Meteoric material entering Earth's atmosphere ablates in the mesosphere and is then expected to recondense into tiny so-called ''smoke particles.'' These particles are thought to be of great importance for middle atmosphere phenomena like noctilucent clouds, polar mesospheric summer echoes, metal layers, and heterogeneous chemistry. Commonly used one-dimensional (1-D) meteoric smoke profiles refer to average global conditions and yield of the order of a thousand nanometer sized particles per cubic centimeter at the mesopause, independent of latitude and time of year. Using the first two-dimensional model of both coagulation and transport of meteoric material we here show that such profiles are too simplistic, and that the distribution of smoke particles indeed is dependent on both latitude and season. The reason is that the atmospheric circulation, which cannot be properly handled by 1-D models, efficiently transports the particles to the winter hemisphere and down into the polar vortex. Using the assumptions commonly used in 1-D studies results in number densities of nanometer sized particles of around 4000 cm À3 at the winter pole, while very few particles remain at the Arctic summer mesopause. If smoke particles are the only nucleation kernel for ice in the mesosphere this would imply that there could only be of the order of 100 or less ice particles cm À3 at the Arctic summer mesopause. This is much less than the ice number densities expected for the formation of ice phenomena (noctilucent clouds and polar mesospheric summer echoes) that commonly occur in this region. However, we find that especially the uncertainty of the amount of material that is deposited in Earth's atmosphere imposes a large error bar on this number, which may allow for number densities up to 1000 cm À3 near the polar summer mesopause. This efficient transport of meteoric material to the winter hemisphere and down into the polar vortex results in higher concentrations of meteoric material in the Arctic winter stratosphere than previously thought. This is of potential importance for the formation of the so-called stratospheric condensation nuclei layer and for stratospheric nucleation processes.