The Effect of Bottle Fill Rate and Pour Technique on the Recovery of Volatile Organics

This field study was conducted to examine whether the method or the flow rate (fill rate) used to fill a sample vial affects recovery of volatile organics (VOCs). To our knowledge, there have not been any systematic studies that have examined this issue. For this field study, three fill rates (50 mL/min, 250 mL/min, and ~1 L/min) and three filling methods (top‐pour, side‐pour, and bottom‐fill) were used to fill sample vials. We found that the bottom‐fill method, with the tubing submerged in the sample as it fills, yielded the greatest recovery (i.e., highest concentrations) of VOCs. Little improvement was observed by pouring down the side of a vial vs. simply pouring straight down from the top. We also found that filling the vials at the fastest fill rate (~1 L/min) yielded higher recovery than the slowest fill rate (50 mL/min) using all three filling methods. These results are counter to prevailing guidance and conventional wisdom that slower filling is preferable to faster filling and that pouring down the side of a sample vial is the best practice for VOC sampling. However, because we were unable to randomize the order the samples were collected with respect to fill rate, we recommend a follow‐on study be conducted that will allow us to confirm our findings and better determine which fill rates minimize losses of VOCs     

Analysis of systematic error in “bead method” measurements of meteorite bulk volume and density

The Archimedean glass bead method for determining meteorite bulk density has become widely applied. We used well characterized, zero-porosity quartz and topaz samples to determine the systematic error in the glass bead method to support bulk density measurements of meteorites for our ongoing meteorite survey. Systematic error varies according to bead size, container size and settling method, but in all cases is less than 3%, and generally less than 2%. While measurements using larger containers (above 150 cm³) exhibit no discernible systematic error but much reduced precision, higher precision measurements with smaller containers do exhibit systematic error. For a 77 cm³ container using 40-80 μm diameter beads, the systematic error is effectively eliminated within measurement uncertainties when a “secured shake” settling method is employed in which the container is held securely to the shake platform during a 5 s period of vigorous shaking. For larger 700-800 μm diameter beads using the same method, bulk volumes are uniformly overestimated by 2%. Other settling methods exhibit sample-volume-dependent biases. For all methods, reliability of measurement is severely reduced for samples below ∼5 cm³ (10-15 g for typical meteorites), providing a lower-limit selection criterion for measurement of meteoritical samples.     

Incompletely compacted equilibrated ordinary chondrites

Abstract— We document the size distributions and locations of voids present within five highly porous equilibrated ordinary chondrites using high‐resolution synchrotron X‐ray microtomography (μCT) and helium pycnometry. We found total porosities ranging from ～10 to 20% within these chondrites, and with μCT we show that up to 64% of the void space is located within intergranular voids within the rock. Given the low (S1‐S2) shock stages of the samples and the large voids between mineral grains, we conclude that these samples experienced unusually low amounts of compaction and shock loading throughout their entire post accretionary history. With Fe metal and FeS metal abundances and grain size distributions, we show that these chondrites formed naturally with greater than average porosities prior to parent body metamorphism. These materials were not “fluffed” on their parent body by impact‐related regolith gardening or events caused by seismic vibrations. Samples of all three chemical types of ordinary chondrites (LL, L, H) are represented in this study and we conclude that incomplete compaction is common within the asteroid belt.     

H/L chondrite LaPaz Icefield 031047 - A feather of Icarus?

Antarctic meteorite LAP 031047 is an ordinary chondrite composed of loosely consolidated chondritic fragments. Its petrography, oxygen isotopic composition and geochemical inventory are ambiguous and indicate an intermediate character between H and L chondrites. Petrographic indicators suggest LAP 031047 suffered a shock metamorphic overprint below ∼10 GPa, which did not destroy its unusually high porosity of ∼27 vol%. Metallographic textures in LAP 031047 indicate heating above ∼700 °C and subsequent cooling, which caused massive transformation of taenite to kamacite. The depletion of thermally labile trace elements, the crystallization of chondritic glass to microcrystalline plagioclase of unusual composition, and the occurrence of coarsely crystallized chondrule fragments is further evidence for post-metamorphic heating to ∼700-750 °C. However, this heating event had a transient character because olivine and low-Ca pyroxene did not equilibrate. Nearly complete degassing up to very high temperatures is indicated by the thorough resetting of LAP 031047’s Ar-Ar reservoir ∼100 ± 55 Ma ago. A noble gas cosmic-ray exposure age indicates it was reduced to a meter-size fragment at <0.5 Ma. In light of the fact that shock heating cannot account for the thermal history of LAP 031047 in its entirety, we test the hypothesis that this meteorite belonged to the near-surface of an Aten or Apollo asteroid that underwent heating during orbital passages close to the Sun.     

Density,magnetic susceptibility,and the characterization of ordinary chondrite falls and showers

Abstract— Bulk and grain densities of 132 ordinary chondrites from the Vatican Observatory collection were measured and compared with their magnetic susceptibility (for the most part using previously measured values; ten new susceptibility measures were taken for this study). Grain density and magnetic susceptibility combined provide a reliable method of classifying unweathered ordinary chondrites. Unlike traditional chemical tests, this method is fast, nondestructive, and characterizes the whole rock, making it especially appropriate for surveying large collections. The system is less viable for finds; extensive weathering of metallic iron in an H chondrite can cause it to plot among L chondrites, while heavily weathered L chondrites plot among the LL group. This system has revealed outlier stones that may be misclassified meteorites or mislabeled samples; in every case where the magnetic susceptibility of a meteorite does not fit its putative classification, the grain density is also found to be in disagreement in a manner consistent with either severe weathering or misidentification. An analysis of stones from five showers shows that, excluding outliers, these samples tend to cluster tightly within their appropriate groups in a plot of grain versus magnetic susceptibility.     

The morphology and surface processes of Comet 19/P Borrelly

The flyby of the nucleus of the Comet 19P/Borrelly by the Deep Space 1 spacecraft produced the best views to date of the surface of these interesting objects. It transformed Borrelly from an astronomical object shrouded in coma of gas and dust into a geological object with complex surface processes and a rich history of erosion and landform evolution. Based on analysis of the highest resolution images, stereo images, photometry, and albedo we have mapped four major morphological units and four terrain features. The morphological units are named dark spots, mottled terrain, mesas, and smooth terrain. The features are named ridges, troughs, pits, and hills. In strong contrast to asteroids, unambiguous impact craters were not observed on Borrelly's surface. Because of the relatively short period of this comet, surface erosion by volatile sublimation is, in geologic terms, a very active process. The formation and the morphologies of units and features appear to be driven by differential rates of sublimation erosion. Erosional rates across the comet are probably controlled by solar energy input and the location of the subsolar point during perihelion. Differences in energy input may produce different varieties of sublimation erosional landforms. The terrains on Borrelly suggest that solar energy input could map directly into erosional processes and landforms.     

Sm---Nd isotopic systematics of a gabbro-eclogite transition

Sm---Nd isotopic systems have been studied in: (1) a sequence of coronitic olivine gabbros showing different degrees of transition to eclogite; (2) coronitic leuco-gabbro norite; and (3) country-rock eclogite, all from the Nordøyane-Brattvåg area, western Norway. Isochrons defined by combinations of whole-rock samples and relict igneous phases give ages of 1198 ± 56 and 1289 ± 48 Ma (olivine gabbro) and 926 ± 70 Ma (leuco-gabbro norite) and have been interpreted in terms of two different episodes of igneous intrusion.

In gabbro with advanced corona formation, relict augite tends to retain its original Nd isotopic composition, while plagioclase may show selective disturbance related to recrystallization and partial replacement by garnet. In completely eclogitized samples, there is a correlation between the degree of isotopic equilibrium and microstructural equilibrium. Whole-rock eclogites occurring within gabbro are characterized by pseudomorphs after igneous phases, and preserve original igneous Nd isotopic composition. Results for eclogite minerals suggest Caledonian ages, but these phases have not achieved complete isotopic equilibrium. In contrast, Nd isotopic systems in texturally equilibrated and strongly deformed eclogite within adjacent gneisses have been disturbed on a whole-rock scale. Minerals from an external eclogite define a Sm---Nd isochron with an age of 400 ± 16 Ma which is interpreted to date synkinematic eclogite equilibration at high-P and -T conditions.