¹Robert J. MACKE,²Cyril OPEIL,¹Guy J. CONSOLMAGNO
Meteoritics & Planetary Society (in Press) Link to Article [https://doi.org/10.1111/maps.13385]
Vatican Observatory, V-00120 Vatican City-State2Department of Physics, Boston College, Chestnut Hill, Massachusetts 02215, USA
Published by arrangement with John Wiley & Sons

Low-temperature specific heat capacities of meteorites provide valuable data forunderstanding the composition and evolution of meteorites and modeling the thermalbehavior of their source asteroids. By liquid nitrogen immersion, we measured average low-temperature heat capacities for 60 ordinary chondrite falls from the Vatican collection. Wefurther characterized the temperature dependence of ordinary chondrite by directmeasurement of Cp(T) over the range 5–320 K for five OC falls, coupled by composition-based models for 94 ordinary chondrites. We find that the heat capacity as a function oftemperature for typical ordinary chondrites can be closely approximated by a third-orderpolynomial in temperature. Furthermore, those polynomial coefficients can be estimatedfrom the single-value average heat capacity measurement. These measurements haveimportant implications for the orbital and spin evolution of S- and Q-type asteroids via thevarious Yarkovsky effects and the thermal evolution of meteorite parent bodies.

^1,3Andreas T. Hertwig,²Makoto Kimura,¹Céline Defouilloy,¹Noriko T. Kita
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13379]
¹WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA 2
²National Institute of Polar Research, Meteorite Research Center, Midoricho 10-3, Tachikawa Tokyo 190-8518, Japan 3
³Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles,
Los Angeles, California 90095, USA
Published by arrangement with John Wiley & Sons

We performed in situ oxygen three-isotope measurements of chondrule olivine,pyroxenes, and plagioclase from the newly described CVRedchondrite NWA 8613.Additionally, oxygen isotope ratios of plagioclase in chondrules from the Kaba CV3OxBchondrite were determined to enable comparisons of isotope ratios and degree of alterationof chondrules in both CV lithologies. NWA 8613 was affected by only mild thermalmetamorphism. The majority of oxygen isotope ratios of olivine and pyroxenes plot along aslope-1 line in the oxygen three-isotope diagram, except for a type II and a remolten barredolivine chondrule. When isotopic relict olivine is excluded, olivine, and low- and high-Capyroxenes are indistinguishable regardingD17O values. Conversely, plagioclase in chondrulesfrom NWA 8613 and Kaba plot along mass-dependent fractionation lines. Oxygen isotopicdisequilibrium between phenocrysts and plagioclase was caused probably by exchange ofplagioclase with16O-poor fluids on the CV parent body. Based on an existing oxygenisotope mass balance model, possible dust enrichment and ice enhancement factors wereestimated. Type I chondrules from NWA 8613 possibly formed at moderately high dustenrichment factors (509to 1509CI dust relative to solar abundances); estimates for waterice in the chondrule precursors range from 0.29to 0.69the nominal amount of ice in dustof CI composition. Findings agree with results from an earlier study on oxygen isotopes inchondrules of the Kaba CV chondrite, providing further evidence for a relatively dry andonly moderately high dust-enriched disk in the CV chondrule-forming region.

^1,2,3S. N. Valencia,¹B. L. Jolliff,¹R. L. Korotev
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13370]
¹Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, Missouri 63130, USA
²Current address: Department of Astronomy, University of Maryland, College Park, Maryland 20742, USA
¹NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
Published by arrangement with John Wiley & Sons

The Northwest Africa (NWA) 773 clan of lunar meteorite stones are coarse‐grained breccias that provide an opportunity to examine a lunar igneous system that includes inferred intrusive and extrusive lithologies, possibly related through a common liquid line of descent from a single source region. Such extensive sampling of a single very low‐Ti (VLT) magmatic system on the Moon is unprecedented among the lunar samples. This study focuses on the olivine gabbro (OG), anorthositic gabbro (AG), and ferroan gabbro (FG) lithologies variably contained in NWA 773, NWA 2727, NWA 3160, NWA 3170, NWA 7007, and NWA 10656. Mineral compositions in the three gabbros indicate the crystallization sequence OG → AG → FG. Petrologic modeling of these three lithologies, and an olivine phyric basalt that also occurs in the NWA 773 clan, however, suggests that the relationship among the lithologies is more complex. The OG and basalt can be modeled as originating from a VLT KREEP‐bearing parental melt similar to the Apollo 14 Green Glass b1 composition through mainly equilibrium crystallization. The AG and FG, however, do not fit this simple model and require either a more complex crystallization sequence involving fractional crystallization, magma chamber recharge, or perhaps heterogeneity in the source region.