^1,2Peter Jenniskens,³Hadrien A. R. Devillepoix
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14321]
¹SETI Institute, Mountain View, California, USA
²NASA Ames Research Center, Moffett Field, California, USA
³Space Science and Technology Centre and International Centre for Radio Astronomy Research, Curtin University, Perth, Western Australia, Australia
Published by arrangement with John Wiley & Sons

With the goal to determine the origin of our meteorites in the asteroid belt, video and photographic observations of meteors have now tracked 75 meteorite falls. Six years ago, there were just hints that different meteorite types arrived on different orbits, but now, the number of orbits (N) is high enough for distinct patterns to emerge. In general, 0.1–1-m sized meteoroids do not arrive on similar orbits as the larger ~1-km sized near-Earth asteroids (NEA) of corresponding taxonomic class. Unlike larger NEA, a group of H chondrite meteoroids arrived on low-inclined orbits from a source just beyond the 5:2 mean-motion resonance with Jupiter (N = 12), three of which have the 7 Ma cosmic ray exposure (CRE) age from a significant collision event among H chondrites. There is also a source of H chondrites low in the inner main belt with a ~35 Ma CRE age (N = 8). In contrast, larger H-like taxonomic S-class NEA arrive from high-inclined orbits out of the 3:1 resonance. Some H chondrites do so also, four of which have a 6 Ma CRE age and two have an 18 Ma CRE age. L chondrites arrive from a single source low in the inner main belt, mostly via the ν6 secular resonance (N = 21), not the 3:1 resonance as most L-like NEA do. LL chondrites arrive too from the inner main belt (N = 5), as do larger LL-like NEA. CM chondrites are delivered from a low i < 3° inclined source beyond the 3:1 resonance (N = 4). Source asteroid families for these meteorite types are proposed, many of which have the same CRE age as the asteroid family’s dynamical age. Also, two HED achondrites are now traced to specific impact craters on asteroid Vesta.

^1,2Dominik C. Hezel,³Knut Metzler,⁴Mara Hochstein
Meteoritics & Plantary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14336]
¹Institut für Geowissenschaften, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
²Department of Mineralogy, Natural History Museum, London, UK
³Institut für Planetologie, University of Münster, Münster, Germany
⁴Department of Geology and Mineralogy, University of Cologne, Köln, Germany
Published by arrangement with John Wiley & Sons

Chondrule size–frequency distributions provide important information to understand the origin of chondrules. Size–frequency distributions are often obtained as apparent 2-D size–frequency distributions in thin sections, as determining a 3-D size–frequency distribution is notoriously difficult. The relationship between a 2-D size–frequency distribution and its corresponding 3-D size–frequency distribution has been previously modeled; however, the results contradict measured results. Models so far predict a higher mean of the 2-D size–frequency distribution than the corresponding mean of the 3-D size–frequency distribution, while the measurements of real chondrule populations show the opposite. Here, we use a new model approach that agrees with these measurements and at the same time offers a solution, why models so far predicted the opposite. Our new model provides a tool with which the 3-D chondrule size–frequency distribution can be determined from the fit of a measured 2-D chondrule size–frequency distribution.