The accumulation rate of meteorite falls at the Earth's surface: The view from Roosevelt County,New Mexico

Abstract— The discovery of 154 meteorite fragments within an 11 km² area of wind-excavated basins in Roosevelt County, New Mexico, permits a new calculation of the accumulation rate of meteorite falls at the Earth's surface. Thermoluminescence dating of the coversand unit comprising the prime recovery surface suggests the maximum terrestrial age of the meteorites to be about 16.0 ka. The 68 meteorite fragments subjected to petrological analyses represent a minimum of 49 individual falls. Collection bias has largely excluded carbonaceous chondrites and achondrites, requiring the accumulation rate derived from the recovered samples to be increased by a factor of 1.25. Terrestrial weathering destroying ordinary chondrites can be modelled as a first-order decay process with an estimated half-life of 3.5 ± 1.9 ka on the semiarid American High Plains. Having accounted for the age of the recovery surface, area of field searches, pairing of finds, collection bias and weathering half-life, we calculate an accumulation rate of 9.4 × 10² falls/a per 10⁶ km² for falls > 10 g total mass. This figure exceeds the best-constrained previous estimate by more than an order of magnitude. One possible reason for this disparity may be the extraordinary length of the fall record preserved in the surficial geology of Roosevelt County. The high accumulation rate determined for the past 16 ka may point to the existence of periods when the meteorite fall rate was significantly greater than at present.     

The non‐trivial problem of meteorite pairing

Abstract— Pairing is the procedure of identifying fragments of a single meteorite fall (that were separated during atmospheric passage or during terrestrial history) by establishing the similarity of two or more meteorite fragments. We argue that pairing is governed by two principles, that only a single mismatch of properties is required to refute a proposed pairing, and that virtually all pairings bear some degree of uncertainty. Using data distributions for modern falls, we take a probability approach to estimate degrees of certainty associated with proposed pairings, emphasizing the importance of unusual features. For new pairing criteria or new analytical additions to old criteria, the degree of variation within individual meteorites must be delineated and the degree of variation within meteorite classes must be quantified. Criteria for pairing can be divided into (1) parent body history indicators, (2) meteoroid space history indicators, and (3) terrestrial history indicators. Included in these categories are 11 specific criteria, including petrographic textures, mineralogy and mineral composition, terrestrial age estimates, cosmic‐ray exposure ages, and natural thermoluminescence (TL) levels. Not all criteria are applicable to all meteorite types. About 2275 pairings suggested in the literature have been subjected to this analysis. Many literature pairings, especially those involving common meteorite types, bear large uncertainties due to lack of data.     

On the problem of the Tunguska meteorite material

The approximate composition of the Tunguska meteorite remnants obtained by averaging the results of several measurements is presented. It is pointed out that the matter of the cosmic-body remnants was enriched with alkaline and alkaline-earth elements. The composition of the meteorite matter was extremely heterogeneous. The upper limit of the density of the Tunguska cosmic body has been estimated at 2.8 g/cm³. It is suggested that, due to interaction with the Earth’s atmosphere, the cosmic body disintegrated into fragments from 10^?7 to 10^?3 m in size, with the majority of the matter being ejected to the upper atmospheric layers. Calculations of the rate and the time of the sedimentation of particles in the atmosphere have shown that the change in atmosphere transparency is controlled by particles larger than 10^?5 m in radius.     

The ideal resonance problem a comparison of two formal solutions I

Garfinkel's solution of the Ideal Resonance problem derived from a Bohlin-von Zeipel procedure, and Jupp's solution, using Poincaré's action and angle variables and an application of Lie series expansions, are compared. Two specific Hamiltonians are chosen for the comparison and both solutions are compared with the numerical solutions obtained from direct integrations of the equations of motion. It is found that in deep resonance the second-mentioned solution is generally more accurate, while in the classical limit the first solution gives excellent agreement with the numerical integrations.This article represents a summary of a much more extensive programme of research, the complete results of which will be published in a future article.     

The ideal resonance problem a comparison of two formal solutions III

This is the last article in a series of the same title. The two formal solutions of the Ideal Resonance Problem, developed respectively by Garfinkel and Jupp, were compared and contrasted in the earlier papers. It was stated there that the principal shortcoming of Jupp's analytical solution was the occurrence of a singularity at the separatrix. The purpose of this contribution is to demonstrate how this singularity may readily be removed. Accordingly, modified solutions are presented for the libration and circulation regions.     

The meteorite of Ensisheim: 1492 to 1992

Abstract— On November 7, 1492, a 127-kg stony meteorite fell at Ensisheim in Alsace after a fireball explosion that was heard for a distance of 150 km over the upper Rhineland. Today, a 56-kg specimen of the stone, an LL6 chondrite with large patches of fusion crust, remains on display in the Hotel de Ville at Ensisheim. This was the earliest witnessed meteorite fall in the West from which pieces are preserved. Initially, the stone's survival depended on the presence of a magistrate at Ensisheim who forbade the removal of pieces, which had begun apace as soon as a crowd gathered and pulled the stone out of a 1-m hole in a wheat field. He ordered the stone brought into the city to await the arrival of King Maximilian, son of the Holy Roman Emperor Friedrich III, who was approaching with his army. In nearby Basel, broadsheets were printed within weeks bearing the story in Latin and German verses by the eminent poet, Sebastian Brant, who turned the sheets into propaganda tracts by claiming the stone as a portent of victory and admonishing Maximilian to make war on the French without delay. Maximilian declared the stone to be a sign of divine favor and ordered it to be preserved in the Ensisheim parish church. The stone grew in fame when Maximilian won his impending battle with the French, but strange new elements entered the story as it was repeated over the years in books and chronicles. Through centuries of battle and political changes, the stone remained in the church until 1793 when French revolutionaries transferred it to a new National Museum in Colmar. There, many pieces were taken for chemical analyses during the birth of the meteoritics at the turn of the 19th century. In 1803 the stone was returned to the Ensisheim church where it outlasted the structure itself which collapsed in 1854. This paper traces the history of the stone itself and people's responses to it through the 500 years since the fall at Ensisheim.     

Comments on the BDT-FRW perfect fluid solutions

It is shown that the BDT-FRW perfect fluid solutions given some years ago by Chauvet and Obregón (1979) are identical to the solutions first given by Jordan (1955) and later by Brill (1962).     

The Mazapil meteorite: From paradigm to periphery

Abstract— The remarkable fact about the Mazapil meteorite is that it fell on the same night, in 1885, that the Andromedid meteor shower underwent a spectacular outburst. The simultaneity of these two events has driven speculation ever since. From ?1886 to ?1950 the circumstances of the Mazapil fall were taken, by a number of researchers, as the paradigm that demonstrated the fact that comets were actually swarms of meteoritic boulders. Beginning ?1950, however, most researchers began to adopted the stance that the timing of the Mazapil fall was nothing more than pure coincidence. The reason behind this change in interpretation stemmed from, amongst other factors, the fact that none of the prominent annual meteor showers could be clearly shown to deliver meteorites. Also, with the introduction of the icy‐conglomerate model for cometary nuclei, by F. Whipple in the early 1950s, it became increasingly clear that only exceptional circumstances would allow for the presence of large meteoritic bodies in cometary streams. Further, by the mid 1960s it had been shown that meteorites could, in fact, be delivered to the Earth from the main belt asteroid region via gravitational resonances. With the removal of the dynamical “barrier” against the delivery of meteorites from the asteroid region, the idea that the Mazapil meteorite could have been part of the Andromedid stream fell into complete disfavor. This being said, we nonetheless present the results of a study concerning the possible properties of the parent object to the Mazapil meteorite based upon the assumption that it was a member of the Andromedid stream. This study is presented to illustrate the point that while cometary showers do not yield meteorites on the ground, this does not, in fact, substantiate the argument that no meteoritic bodies reside in cometary streams. Indeed, we find no good reason to suppose that an object with the characteristics of the Mazapil meteorite could not have been delivered from the Andromedid stream. However, we argue that upon the basis of the actual reported observations and upon the scientific maxim of minimized hypothesis and least assumption it must be concluded that the timing of the fall of the Mazapil meteorite and the occurrence of the Andromedid outburst were purely coincidental.     

The ideal resonance problem,a comparison of two formal solutions,II

This paper is a sequel to an earlier article of the same title. The two formal analytical solutions of the Ideal Resonance Problem developed respectively by Garfinkel and Jupp are here compared, atsecond-order in the appropriate small parameter, with numerical integrations; the second-order circulation solution for Jupp's theory being presented for the first time. It transpires that throughout most of the deep resonance regime the second-mentioned solution provides greater accuracy. In addition, it is demonstrated that the first solution is not appropriate when general initial values of the variables are prescribed.     

Existence of quasi-periodic solutions to the three-body problem

A rigorous proof is given for the existence of quasi-periodic solutions with only two degrees of freedom to a planar three-body problem. The solution corresponds physically to the small bodies moving on different, nearly elliptical orbits about a large mass located at a focus. The perihelia of the two orbits are locked in such a way that the difference of the two perihelia has mean value zero.     

The multiple meteorite fall of Neuschwanstein: Circumstances of the event and meteorite search campaigns

Abstract— A large meteorite fall in southern Germany on April 6, 2002 was captured by camera stations of the European Fireball Network (EN) which routinely monitors the night sky over central Europe. From analysis of the images, a prediction on the geographic location of the meteorite strewn field could be made. Following systematic ground searches in difficult high‐mountain terrain, three fragments of a rare EL6 enstatite chondrite were recovered during search campaigns in the summers of 2002 and 2003. “Neuschwanstein” is the fourth meteorite fall in history that has been photographed by fireball networks and the fragments of which have been found subsequently. It is the first time since the beginning of the EN operation in the early sixties that the photographic observations have made a meteorite recovery possible.     

Comments on the application of power series solutions to problems in celestial mechanics

The author relates his experiences in utilizing the power series method to generate trajectories for orbital and sub-orbital vehicles and for then-body problem.     

Comments on the comment on the Guzman-Bianchi type-VII h solutions

In this paper, we again discuss the new Brans-Dicke-Bianchi type-VII _h perfect fluid solutions, first given by us (Guzman, 1989). It is shown that the objections presented by Lorenz-Petzold (1989) are misleading. The dust case =0 is discussed.     

Comments on the BDT-FRW solutions with a cosmological constant

Some critical comments are made on the power-law solutions recently given by Pimentel (1985) on the basis of the Brans-Dicke field equations for Friedmann-Robertson-Walker space-times.     

The nature of the Tunguska meteorite

Abstract— Arguments in favor of the cometary origin of the Tunguska meteorite are adduced along with reasons against the asteroidal hypothesis. A critical analysis is given for the hypotheses by Sekanina (1983) and Chyba et al. (1993). On the basis of the azimuth and inclination of the trajectory of the Tunguska body with plausible values of the geocentric velocity, the semimajor axis of the orbit and its inclination to the ecliptic plane are calculated for this body. It is noted that the theory of the disintegration of large bodies in the atmosphere put forward by Chyba et al. (1993) is crude. Applying more accurate theories (Grigoryan, 1979; Hills and Goda, 1993) as well as taking into account the realistic shape of the body yield for the cometary body lower disruption heights than obtained by Chyba et al. Numerical simulations carried out by Svettsov et al. agree well with the cometary hypothesis and the analytical calculations based on Grigoryan's theory. The asteroidal hypothesis is shown not to be tenable: the complete lack of stony fragments in the region of the catastrophe, cosmochemical data (in particular, the results of an isotope analysis), and some other information contradict this hypothesis. It is shown that stony fragments that would have originated in the explosive disruption of the Tunguska body would not be vaporized by the radiation of the vapor cloud nor as a result of their fall to the Earth's surface.     

The orbit of the Dhajala meteorite

Observations of the trail caused by the meteorite which fell around Dhajala, Gujarat (India), on 28 January 1976 have been used to compute the probable orbit of the meteoroid in space. The cosmic ray effects in the meteorite fragments indicate high mass ablation (?90%), suggesting a high velocity (?20 km/sec) of entry into the Earth's atmosphere. The atmospheric trajectory is reasonably well documented and its deviation from the projected ground fallout can be understood in terms of the ambient wind pattern. The apparent radiant of the trail was at a point in the sky with right ascension 165°, declination +60°. Considering the errors in estimating the radiant, we get a range of orbits with a = 2.3 ± 0.8 AU, e = 0.6 ± 0.1, and i = 28 ± 4° with the constraints of a ? 1.5 AU and V_∞ < 25 km/sec (which causes nearly complete evaporation of the meteoroid). Taking V_∞ = 21.5 lm/sec as indicated by the measured mass ablation of the meteorite, the orbital elements are deduced to be $\text{a = 1.8}\text{AU}\text{, e = 0.59, i = 27°.6, ω = 109°.1, Ω = 307°.8,}\text{and}\text{q = 0.74}$.     

The fall of the St-Robert meteorite

Abstract The St-Robert (Québec, Canada) meteorite shower occurred on 1994 June 15 at 0h02m UT accompanied by detonations audible for >200 km from the fireball endpoint. The fireball was recorded by visual observers in Vermont, New York State, New Hampshire, Québec and Ontario as well as by optical and infrared sensors in Earth-orbit. Penetration to an altitude of 36 km occurred ～60 km to the northeast of Montreal, where the bolide experienced several episodes of fragmentation. A total of 20 fragments of this H5 chondrite, comprising a total mass of 25.4 kg, were recovered in an ellipse measuring 8 × 3.5 km. One fragment of the shower partially penetrated the aluminum roof of a shed. Interpretation of the visual and satellite data suggests that the fireball traveled from south-southwest to north-northeast, with a slope from the horizontal of 55°–61°. A statistical evaluation of the likely heliocentric orbits for the body prior to collision with the Earth, coupled with theoretical modeling of the entry, suggests an entry velocity in the range of 12.7–13.3 km/s; the meteoroid had moved in a low-inclination orbit, with orbital perihelion located extremely close to the Earth's orbit. From satellite optical data, it is found that the photometric mass consumed during the largest detonation is ～1200 kg. Estimation of the amplitude of the acoustic signal detected by the most distant observer yields a source energy near 0.5 kt TNT equivalent energy, which corresponds to a mass of order 10 metric tonnes. This measure is uncertain to approximately one order of magnitude. Theoretical modeling of the entry of the object suggests a mass near 1600 kg. Cosmogenic radionuclide activities constrain the lower initial mass to be ～700 kg with an upper limit near 4000 kg. Seismic data possibly associated with the fireball suggest extremely poor coupling between the airwave and the ground. The total mass estimated to have reached the ground is ～100 kg (in material comprising >55 g fragments), while the preatmospheric mass is found to be most probably in the range of 1200–2000 kg.     

An improbable concentration of basaltic meteorite falls (HED and mesosiderite) in the mid-20th century

Abstract The fall rate of HED basaltic meteorites (howardites, eucrites, diogenites) has not been constant in the 20th century, while the fall rate of chondrites has been constant within error. Thirteen of the 26 dated HED falls (day of fall known, 1900 through 1989) fell in 1924 through 1939. A fall cluster (not a meteorite stream) like this will occur in less than one in 100 random distributions of fall days. The proportions of HED types in the whole cluster are statistically identical to those of the whole historical record of HED falls, as is the distribution of cosmic ray exposure ages. In a subset of the cluster, 1924 through 1933, eight of those nine HED falls from have exposure ages of 10–20 Ma; this grouping is statistically distinct from that of the historical record. The mesosiderite meteorites share many chemical and isotopic properties with the HEDs but are not from the same parent body. However, the dates of the three mesosiderite falls of the 20th century (all in 1924 through 1939) are a likely sampling of the distribution of HED fall dates; less than one in 200 random distributions of three fall dates would have them all in a given IS year interval of the 20th century. If the concentration of HED and mesosiderite falls in 1924 through 1939 is not a result of chance (odds of less than 1 in 200), it must have had a cause or causes. The cause(s) are not dear but appear(s) to have operated: on parent bodies only of basaltic meteorites; on a number of such parent bodies (mesosiderite and at least one HED); distant from Earth; and so as to produce a duster of only 15 years duration. This duration is much shorter than the expected time scales or orbital evolution of asteroidal fragments.