The mass of extraterrestrial material accreted by the Earth as submillimeter particles has not previously been measured with a single direct and precise technique that samples the particle sizes representing most of that mass. The flux of meteoroids in the mass range 10(-9) to 10(-4) grams has now been determined from an examination of hypervelocity impact craters on the space-facing end of the Long Duration Exposure Facility satellite. The meteoroid mass distribution peaks near 1.5 x 10(-5) grams (200 micrometers in diameter), and the small particle mass accretion rate is (40 +/- 20) x 106 kilograms per year, higher than previous estimates but in good agreement with total terrestrial mass accretion rates found by geochemical methods. This mass input is comparable with or greater than the average contribution from extraterrestrial bodies in the 1-centimeter to 10-kilometer size range.

https://science.sciencemag.org/content/sci/262/5133/550.full.pdf

A direct measurement of the terrestrial mass accretion rate of cosmic dust.

Meteoroids can be observed at collision with the Earth's atmosphere as meteors. Different methods of observing meteors are presented: besides the traditional counts of individual events, exact methods yield also data on the geometry of the atmospheric trajectory; on the dynamics and ablation of the body in the atmosphere; on radiation; on the spectral distribution of radiation; on ionization; on accompanying sounds; and also data on orbits. Theoretical models of meteoroid interaction with the atmosphere are given and applied to observational data. Attention is paid to radar observations; to spectroscopic observations; to experiments with artificial meteors and to different types of meteor sounds. The proposed composition and structure of meteoroids as well as their orbits link them to meteorites, asteroids and comets. Meteor streams can be observed as meteor showers and storms. The rate of influx of meteoroids of different sizes onto Earth is presented and potential hazards discussed.

Meteor Phenomena and Bodies

The asteroid impact near the Russian city of Chelyabinsk on 15 February 2013 was the largest airburst on Earth since the 1908 Tunguska event, causing a natural disaster in an area with a population exceeding one million. Because it occurred in an era with modern consumer electronics, field sensors, and laboratory techniques, unprecedented measurements were made of the impact event and the meteoroid that caused it. Here, we document the account of what happened, as understood now, using comprehensive data obtained from astronomy, planetary science, geophysics, meteorology, meteoritics, and cosmochemistry and from social science surveys. A good understanding of the Chelyabinsk incident provides an opportunity to calibrate the event, with implications for the study of near-Earth objects and developing hazard mitigation strategies for planetary protection.

/pdf/chelyabinsk-airburst-damage-assessment-meteorite-recovery-2cr5je8h68.pdf

Chelyabinsk airburst, damage assessment, meteorite recovery, and characterization

Real-time determination of meteor-related parameters utilizing modern digital technology

The zodiacal cloud is a thick circumsolar disk of small debris particles produced by asteroid collisions and comets. Their relative contribution and how particles of different sizes dynamically evolve to produce the observed phenomena of light scattering, thermal emission, and meteoroid impacts are unknown. Until now, zodiacal cloud models have been phenomenological in nature, composed of ad hoc components with properties not understood from basic physical processes. Here, we present a zodiacal cloud model based on the orbital properties and lifetimes of comets and asteroids, and on the dynamical evolution of dust after ejection. The model is quantitatively constrained by Infrared Astronomical Satellite (IRAS) observations of thermal emission, but also qualitatively consistent with other zodiacal cloud observations, with meteor observations, with spacecraft impact experiments, and with properties of recovered micrometeorites (MMs). We find that particles produced by Jupiterfamily comets (JFCs) are scattered by Jupiter before they are able to orbitally decouple from the planet and drift down to 1 AU. Therefore, the inclination distribution of JFC particles is broader than that of their source comets and leads to good fits to the broad latitudinal distribution of fluxes observed by IRAS. We find that 85%–95% of the observed mid-infrared emission is produced by particles from JFCs and 100 μm undergo a further collisional cascade with smaller fragments being progressively more affected by Poynting–Robertson (PR) drag. Upon reaching D 10 4 times brighter during the Late Heavy Bombardment (LHB) epoch ≈3.8 Gyr ago, when the outer planets scattered numerous comets into the inner solar system. The bright debris disks with a large 24 μm excess observed around mature stars may be an indication of massive cometary populations existing in those systems. We estimate that at least ∼10 22 , ∼2 × 10 21 , and ∼2 × 10 20 go f

/pdf/cometary-origin-of-the-zodiacal-cloud-and-carbonaceous-5c8cvhm6dd.pdf

Cometary origin of the zodiacal cloud and carbonaceous micrometeorites. implications for hot debris disks

We present the basic differential equations of meteor physics (the single body equations) We solve them numerically including two possible types of fragmentation: into large pieces and into a cluster of small fragments We have written a Fortran code that computes the motion, ablation and light intensity of a meteoroid at chosen heights, and allows for the ablation and shape density coefficients σ and K, as well as the luminous efficiency τ, to be variable with height/time We calibrated our fragmentation model (FM) by the best fit to observational values for the motion, ablation, radiation, fragmentation and the terminal masses (recovered meteorites) for the Lost City bolide The FM can also handle multiple and overlapping meteor flares We separately define both the apparent and intrinsic values of σ, K, and τ We present in this paper values of the intrinsic luminous efficiency as function of velocity, mass, and normalized air density Detailed results from the successful application of the FM to the Lost City, Innisfree, and Benesov bolides are also presented Results of applying the FM to 15 bolides with very precise observational data are presented in a survey mode (Table 7) Standard deviations of applying our FM to all these events correspond to the precision of the observed values Typical values of the intrinsic ablation coefficient are low, mostly in the range from 0004 to 0008 s2 km^(-2), and do not depend on the bolide type The apparent ablation coefficients reflect the process of fragmentation The bolide types indicate severity of the fragmentation process The large differences of the "dynamic" and "photometric" mass from numerous earlier studies are completely explained by our FM The fragmentation processes cannot be modeled simply by large values of the apparent ablation coefficient and of the apparent luminous efficiency Moreover, our new FM can also well explain the radiation and full dynamics of very fast meteoroids at heights from 200 km to 130 km

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1945-5100.2005.tb00363.x

Fragmentation model of meteoroid motion, mass loss, and radiation in the atmosphere

ON 9 October 1992, a bright fireball appeared over West Virginia, travelled some 700 km in a northeasterly direction, and culminated in at least one impact: a 12.4-kg ordinary chondrite was recovered in Peekskill, New York1. Fortuitously, the event was captured on several video recordings, which provide a detailed record of both the fragmentation of the object and related atmospheric effects. These are the first motion pictures of a fireball from which a meteorite has been recovered. We report here the preliminary analysis of 14 video recordings of the event, from which we determine the ground path and the original orbit of the object.

The orbit and atmospheric trajectory of the Peekskill meteorite from video records

The recent discovery of several asteroids in the 10- to 100- m size range by the Spacewatch Telescope has linked the flux data for large meteoroids with the range for asteroids. Cumulative number fluxes and incremental mass fluxes are given in Figs. 1 and 3 as functions of mass. The total influx of interplanetary bodies and dust to the Earth in a wide mass range from 10 −21 kg to 10 15 kg results in 1.7×10 8 kg per year for the entire Earth's surface.

Z. Ceplecha

Papers

Meteor Phenomena and Bodies

Fragmentation model of meteoroid motion, mass loss, and radiation in the atmosphere

The orbit and atmospheric trajectory of the Peekskill meteorite from video records

Influx of Interplanetary Bodies onto Earth

Influx of interplanetary bodies onto Earth