I have determined the composition via INAA of a bulk pristine sample of the Tagish Lake carbonaceous chondrite fall, along with bulk samples of the CI chondrite Orgueil and of several CM chondrites. Tagish Lake has a mean of refractory lithophile element/Cr ratios like those of CM chondrites, and distinctly higher than the CI chondrite mean. Tagish Lake exhibits abundances of the moderately volatile lithophile elements Na and K that are slightly higher than those of mean CM chondrites. Refractory through moderately volatile siderophile element abundances in Tagish Lake are like those of CM chondrites. Tagish Lake is distinct from CM chondrites in abundances of the most volatile element. Mean CI-normalized Se/Co, Zn/Co and Cs/Co for Tagish Lake are 0.68 +/- 0.01, 0.71 +/- 0.07 and 0.76 +/- 0.02, while for all available CM chondrite determinations, these ratios lie between 0.31-0.61, 0.32-0.58 and 0.39-0.74, respectively. Considering petrography, and oxygen isotopic and elemental compositions, Tagish Lake is an ungrouped member of the carbonaceous chondrite clan. The overall abundance pattern is similar to those of CM chondrites, indicating that Tagish Lake and CMs experienced very similar nebular fractionations. Bells is a CM chondrite with unusual petrologic characteristics. Bells has a mean CI-normalized refractory lithophile element/Cr ratio of 0.96, lower than for any other CM chondrite, but shows CI-normalized moderately volatile lithophile element/Cr ratios within the ranges of other CM chondrites, except for Na which is low. Iridium, Co, Ni and Fe abundances are like those of CM chondrites, but the moderately volatile siderophile elements, Au, As and Sb, have abundances below the ranges for CM chondrites. Abundances of the moderately volatile elements Se and Zn of Bells are within the CM ranges. Bells is best classified as an anomalous CM chondrite.

In this paper we describe the recovery, handling and preliminary mineralogical investigation of the Tagish Lake meteorite. Tagish Lake is a type 2 carbonaceous chondrite which bears similarities to CI1 and CM chondrite groups, but is distinct from both. Abundant phyllosilicates as well as chondrules (however sparse) and common olivine grains in the matrix preclude any other classification. The bulk density of Tagish Lake (1.67 g/cc), which is far lower than CI or CM chondrites (2.2-2.3 and 2.6-2.9 g/cc, respectively), or any other meteorite for that matter. We have identified two lithologies: a dominant carbonate-poor lithology and a less-abundant carbonate-rich lithology. The meteorite is a breccia at all scales. We have noted similarities between Tagish Lake and some clasts within the enigmatic meteorite Kaidun; possibly there are genetic relationships here worth exploring. In the paper we describe a clast of CM1 material within Tagish Lake which is very similar to a major lithology in Kaidun.

We have studied the carbon and nitrogen stable isotope geochemistry of a small pristine sample of the Tagish Lake carbonaceous chondrite by high resolution stepped combustion mass spectrometry, and compared the results with data from the Orgueil (CI1), EET 83334 (CM1) and Murchison (CM2) chondrites. The small chip of Tagish Lake analysed herein had a higher carbon abundance (5.81 wt%) than any other chondrite, and a nitrogen content (~1220 ppm) between that of CI1 and CM2 chondrites. Owing to the heterogeneous nature of the meteorite, the measured carbon abundance might be artificially high: the carbon inventory and whole rock carbon isotopic composition (delta-13C is approximately equal to +24.4 ppm) of the chip was dominated by 13C-enriched carbon from the decomposition of carbonates (between 1.29 and 2.69 wt%; delta-13C is approximately equal to +67 ppm and delta-18O is approximately equal to +35 ppm, in the proportions ~4:1 dolomite to calcite). In addition to carbonates, Tagish Lake contains organic carbon (~2.6 wt%; delta-13C is approximately equal to -9 ppm; 1033 ppm N, delta-15N is approximately equal to +77 ppm), a level intermediate between CI and CM chondrites. Around 2% of the organic material is thermally labile and solvent soluble. A further ~18% of the organic species are liberated by acid hydrolysis. Tagish Lake also contains a complement of presolar grains. It has a higher nanodiamond abundance (~3650-4330 ppm) than other carbonaceous chondrites, along with ~8 ppm silicon carbide. Whilst carbon and nitrogen isotope geochemistry is not diagnostic, the data are consistent with classification of Tagish Lake as a CI2 chondrite.

We present instrumental observations of the Tagish Lake fireball and interpret the observed characteristics in the context of two different models of ablation. From these models we estimate the pre‐atmospheric mass of the Tagish Lake meteoroid to be ~56 tonnes and its porosity to be between 37 and 58%, with the lowest part of this range most probable. These models further suggest that some 1300 kg of gram‐sized or larger Tagish Lake material survived ablation to reach the Earth's surface, representing an ablation loss of 97% for the fireball. Satellite recordings of the Tagish Lake fireball indicate that 1.1 x 10^12 J of optical energy were emitted by the fireball during the last 4 s of its flight. The fraction of the total kinetic energy converted to light in the satellite pass band is found to be 16%. Infrasonic observations of the airwave associated with the fireball establish a total energy for the event of 1.66 +/- 0.70 kT TNT equivalent energy. The fraction of this total energy converted to acoustic signal energy is found to be between 0.10 and 0.23%. Examination of the seismic recordings of the airwave from Tagish Lake have established that the acoustic energy near the sub‐terminal point is converted to seismic body waves in the upper‐most portion of the Earth's crust. The acoustic energy to seismic energy coupling efficiency is found to be near 10^(-6) for the Tagish Lake fireball. The resulting energy estimate is near 1.7 kT, corresponding to a meteoroid 4 m in diameter. The seismic record indicates extensive, nearly continuous fragmentation of the body over the height intervals from 50 to 32 km. Seismic and infrasound energy estimates are in close agreement with the pre‐atmospheric mass of 56 tonnes established from the modeling. The observed flight characteristics of the Tagish Lake fireball indicate that the bulk compressive strength of the pre‐atmospheric Tagish Lake meteoroid was near 0.25 MPa, while the material compressive strength (most appropriate to the recovered meteorites) was closer to 0.7 MPa. These are much lower than values found for fireballs of ordinary chondritic composition. The behavior of the Tagish Lake fireball suggests that it represents the lowest end of the strength spectrum of carbonaceous chondrites or the high end of cometary meteoroids. The bulk density and porosity results for the Tagish Lake meteoroid suggest that the low bulk densities measured for some small primitive bodies in the solar system may reflect physical structure dominated by microporosity rather than macroporosity and rubble‐pile assemblages.

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.