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Significance The origin of diamonds in ureilites is still a debated issue among the scientific community, with significant implications for the sizes of early Solar System bodies. We investigated three diamond-bearing ureilites by a multimethodological approach using scanning electron microscopy, micro X-ray diffraction, transmission electron microscopy, and micro-Raman spectroscopy, with the aim of determining the origin of the diamonds. Our results show that formation of both microdiamonds and nanodiamonds in ureilites can be explained by impact shock events on a small planetesimal and does not require long growth times at high static pressures within a Mercury- or Mars-sized body., The origin of diamonds in ureilite meteorites is a timely topic in planetary geology as recent studies have proposed their formation at static pressures >20 GPa in a large planetary body, like diamonds formed deep within Earth’s mantle. We investigated fragments of three diamond-bearing ureilites (two from the Almahata Sitta polymict ureilite and one from the NWA 7983 main group ureilite). In NWA 7983 we found an intimate association of large monocrystalline diamonds (up to at least 100 µm), nanodiamonds, nanographite, and nanometric grains of metallic iron, cohenite, troilite, and likely schreibersite. The diamonds show a striking texture pseudomorphing inferred original graphite laths. The silicates in NWA 7983 record a high degree of shock metamorphism. The coexistence of large monocrystalline diamonds and nanodiamonds in a highly shocked ureilite can be explained by catalyzed transformation from graphite during an impact shock event characterized by peak pressures possibly as low as 15 GPa for relatively long duration (on the order of 4 to 5 s). The formation of “large” (as opposed to nano) diamond crystals could have been enhanced by the catalytic effect of metallic Fe-Ni-C liquid coexisting with graphite during this shock event. We found no evidence that formation of micrometer(s)-sized diamonds or associated Fe-S-P phases in ureilites require high static pressures and long growth times, which makes it unlikely that any of the diamonds in ureilites formed in bodies as large as Mars or Mercury.

The IAU Working Group on Meteor Shower Nomenclature was established in 2006 to regulate the nomenclature of meteor showers reported in the scientific literature. One year later the International Astronomical Union Meteor Data Center shower database was implemented (IAU MDC). The database does not contain all information about the meteor showers. Its purpose is to give each new meteoroid stream, published in the scientific literature, a unique name and codes. During the “Meteoroids 2019” conference held in Bratislava, the IAU Working Group on Meteor Shower Nomenclature established new rules for the introduction and removal of meteor showers from the MDC. In this paper, we present a concise description of the meteor shower database, its origin, and struc- ture and, in particular, the current requirements for the introduction of new data, and unknown as well as known meteor showers.

This work was supported by the Ministry of Science and Higher Education of the Russian Federation, project № FEUZ-2020-0060 and by Act 211 of the Government of the Russian Federation, agreement № 02.A03.21.0006.

The thermal history of carbon phases, including graphite and diamond, in the ureilite meteorites has implications for the formation, igneous evolution, and impact disruption of their parent body early in the history of the Solar System. Geothermometry data were obtained by micro-Raman spectroscopy on graphite in Almahata Sitta (AhS) ureilites AhS 72, AhS 209b and AhS A135A from the University of Khartoum collection. In these samples, graphite shows G-band peak centers between 1578 and 1585 cm−1 and the full width at half maximum values correspond to a crystallization temperature of 1266 °C for graphite for AhS 209b, 1242 °C for AhS 72, and 1332 °C for AhS A135A. Recent work on AhS 72 and AhS 209b has shown graphite associated with nanodiamonds and argued that this assemblage formed due to an impact-event. Our samples show disordered graphite with a crystalline domain size ranging between about 70 and 140 nm. The nanometric grain-size of the recrystallized graphite indicates that it records a shock event and thus argues that the temperatures we obtained are related to such an event, rather than the primary igneous processing of the ureilite parent body.

Almahata Sitta (AhS), an anomalous polymict ureilite, is the first meteorite observed to originate from a spectrally classified asteroid (2008 TC3). However, correlating properties of the meteorite with those of the asteroid is not straightforward because the AhS stones are diverse types. Of those studied prior to this work, 70–80% are ureilites (achondrites) and 20–30% are various types of chondrites. Asteroid 2008 TC3 was a heterogeneous breccia that disintegrated in the atmosphere, with its clasts landing on Earth as individual stones and most of its mass lost. We describe AhS 91A and AhS 671, which are the first AhS stones to show contacts between ureilitic and chondritic materials and provide direct information about the structure and composition of asteroid 2008 TC3. AhS 91A and AhS 671 are friable breccias, consisting of a C1 lithology that encloses rounded to angular clasts (

EgeUn###, The Sariçiçek howardite meteorite shower consisting of 343 documented stones occurred on September 2, 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Sariçiçek experienced a complex cosmic-ray exposure history, exposed during ~12–14 Ma in a regolith near the surface of a parent asteroid, and that an ~1 m sized meteoroid was launched by an impact 22 ± 2 Ma ago to Earth (as did one-third of all HED meteorites). SIMS dating of zircon and baddeleyite yielded 4550.4 ± 2.5 Ma and 4553 ± 8.8 Ma crystallization ages for the basaltic magma clasts. The apatite U-Pb age of 4525 ± 17 Ma, K-Ar age of ~3.9 Ga, and the U,Th-He ages of 1.8 ± 0.7 and 2.6 ± 0.3 Ga are interpreted to represent thermal metamorphic and impact-related resetting ages, respectively. Petrographic; geochemical; and O-, Cr-, and Ti-isotopic studies confirm that Sariçiçek belongs to the normal clan of HED meteorites. Petrographic observations and analysis of organic material indicate a small portion of carbonaceous chondrite material in the Sariçiçek regolith and organic contamination of the meteorite after a few days on soil. Video observations of the fall show an atmospheric entry at 17.3 ± 0.8 km s -1 from NW; fragmentations at 37, 33, 31, and 27 km altitude; and provide a pre-atmospheric orbit that is the first dynamical link between the normal HED meteorite clan and the inner Main Belt. Spectral data indicate the similarity of Sariçiçek with the Vesta asteroid family (V-class) spectra, a group of asteroids stretching to delivery resonances, which includes (4) Vesta. Dynamical modeling of meteoroid delivery to Earth shows that the complete disruption of a ~1 km sized Vesta family asteroid or a ~10 km sized impact crater on Vesta is required to provide sufficient meteoroids ?4 m in size to account for the influx of meteorites from this HED clan. The 16.7 km diameter Antionia impact crater on Vesta was formed on terrain of the same age as given by the 4 He retention age of Sariçiçek. Lunar scaling for crater production to crater counts of its ejecta blanket show it was formed ~22 Ma ago. © The Meteoritical Society, 2019., 58261, 40339 nccr – on the move NNX14AM62G MFAG/113F035 Simons Foundation: 302497 NNX14-AR92G, NNX16AD34G Academy of Finland: 299543 Government Council on Grants, Russian Federation: ? 02., A03.21.0006 Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung: PZ00P2_154874 Ministry of Education and Science of the Russian Federation: 3.1959.2017/4.6 National Natural Science Foundation of China: 41403055, Acknowledgments—We thank N. Ergu€n and family in the village of Sari©ci©cek for donating the meteorites studied here and collecting meteorite fall coordinates. We thank E. Atalan and S. Ozdemir€ at Bingo€l University, and E. Necip Yardım and M. C© i©cek at Mu©s Alparslan University, for facilitating our research at the campuses, and S. Pamuk at the Bingo€l police headquarters. We thank A. and T. Ozdum€ an, police officers in Bingo€l, for assisting with the field study. For technical assistance, we further acknowledge support from M. Fehr, Y.-J. Lai, and L. Hoffland (NASA Ames Research Center); David Mittlefehldt (NASA JSC); K. Wimmer (Ries Crater Museum); J. Sanchez (Planetary Science Institute); A. Neesemann (Free University Berlin); S. Atanasova-Vladimirova and I. Piroeva (Institute of Physical Chemistry, BAS); and B. Georgieva and V. Strijkova (Institute of Optical Materials and Technologies, BAS). This work was supported by Istanbul University (Project No. 40339 and 58261), the Scientific and Technological Research Council of Turkey (MFAG/113F035), the Swiss National Science foundation (PZ00P2_154874 and NCCR PlanetS), the Ministry of Science and Higher Education of the Russian Federation (Project # 3.1959.2017/4.6), Act 211 of the Government of the Russian Federation, contract ? 02.A03.21.0006, the National Natural Science Foundation of China (41403055), the Simons Foundation (302497), the Academy of Finland (299543), the NASA Cosmochemistry Program (NNX14AM62G), the NASA Emerging Worlds Program (NNX16AD34G), and the NASA NEOO program (NNX14-AR92G).

It has been proposed that all L chondrites resulted from an ongoing collisional cascade of fragments that originated from the formation of the ~500Ma old asteroid family Gefion, located near the 5:2 mean-motion resonance with Jupiter in the middle Main Belt. If so, L chondrite pre-atmospheric orbits should be distributed as expected for that source region. Here, we present contradictory results from the orbit and collisional history of the October 24, 2015, L6 ordinary chondrite fall at Creston, CA (here reclassified to L5/6). Creston's short 1.30±0.02 AU semimajor axis orbit would imply a long dynamical evolution if it originated from the middle Main Belt. Indeed, Creston has a high cosmic ray exposure age of 40–50Ma. However, Creston's small meteoroid size and low 4.23±0.07° inclination indicate a short dynamical lifetime against collisions. This suggests, instead, that Creston originated most likely in the inner asteroid belt and was delivered via the ν 6 resonance. The U-Pb systematics of Creston apatite reveals a Pb-Pb age of 4,497.1±3.7Ma, and an upper intercept U-Pb age of 4,496.7±5.8Ma (2σ), circa 70Ma after formation of CAI, as found for other L chondrites. The K-Ar (age ~4.3Ga) and U,Th-He (age ~1Ga) chronometers were not reset at ~500Ma, while the lower intercept U-Pb age is poorly defined as 770±320Ma. So far, the three known L chondrites that impacted on orbits with semimajor axes a 3Ga) K-Ar ages. This argues for a source of some of our L chondrites in the inner Main Belt. Not all L chondrites originate in a continuous population of Gefion family debris stretching across the 3:1 mean-motion resonance.

The asteroid impact near the Russian city of Chelyabinsk on 15 February 2013 was the largest airburst on Earth since the 1908 Tunguska event, causing a natural disaster in an area with a population exceeding one million. Because it occurred in an era with modern consumer electronics, field sensors, and laboratory techniques, unprecedented measurements were made of the impact event and the meteoroid that caused it. Here, we document the account of what happened, as understood now, using comprehensive data obtained from astronomy, planetary science, geophysics, meteorology, meteoritics, and cosmochemistry and from social science surveys. A good understanding of the Chelyabinsk incident provides an opportunity to calibrate the event, with implications for the study of near-Earth objects and developing hazard mitigation strategies for planetary protection

International audience; On July 19 2011 UT, the (90) Antiope double system occulted a 6.7-mag star (LQ Aquarii) with a path predicted to pass over much of northern California. The shape and separation of the components were predicted based on Descamps et al. (2009) model, plus additional Keck AO observations (Merline, Neyman, Tamblyn, Owen) collected on July 13 and 15, 2011 UT. Through a large collaboration in cooperation with the IOTA we organized a campaign of bservations involving 42 observers and 92 stations spread along the path of the occultation in northern California, Nevada, and Idaho to sample both components. The stellar occultation was successfully recorded by 41 stations with a maximum duration of ~33 s. A preliminary analysis of the data that are being processed and analyzed shows that an improved shape model of both components could be derived based on this campaign. We will present the final analysis of this campaign, which allow us to derive a more accurate period and separation for the binary system and also an improved density. We will discuss the origin of (90) Antiope based on the detection of a large concavity, possibly interpreted as a large impact crater on one of the components, already suggested by Descamps et al (2009). This research is partially supported by the NSF grant AAG-0807468, NASA grant NNX11AD62G and CNRS. We thank the many other members of IOTA who took part in this campaign.

Selected area electron diffraction is used to monitor structural changes of vapor-deposited water ice in vacuum during warm-up from 15 to 188 K. A progression of three amorphous forms of water ice is found with well-defined transitions. The formation of a high-density amorphous form (Iah) at 15 K is confirmed, and the transition to the more familiar low-density form (Ial) occurs gradually over the range 38 to 68 K. At 131 K, the ice transforms into a third amorphous form (Iar), which precedes the crystallization of cubic ice (Ic) and coexists metastably with Ic from 148 K until at least 188 K. These structural transformations of amorphous water ice can be used to explain hitherto anomalous properties of astrophysical ices. The structural transition from Iah to Ial is responsible for the diffusion and recombination of radicals in ultraviolet-photolyzed interstellar ices at low temperatures. The occurrence and persistence of Iar explains anomalous gas retention and gas release from water-rich ices at temperatures above 150 K.

The Stardust mission returned cometary, interplanetary and (probably) interstellar dust in 2006 to Earth that have been analysed in Earth laboratories worldwide. Results of this mission have changed our view and knowledge on the early solar nebula. The Rosetta mission is on its way to land on comet 67P/Churyumov-Gerasimenko and will investigate for the first time in great detail the comet nucleus and its environment starting in 2014. Additional astronomy and planetary space missions will further contribute to our understanding of dust generation, evolution and destruction in interstellar and interplanetary space and provide constraints on solar system formation and processes that led to the origin of life on Earth. One of these missions, SARIM-PLUS, will provide a unique perspective by measuring interplanetary and interstellar dust with high accuracy and sensitivity in our inner solar system between 1 and 2 AU. SARIM-PLUS employs latest in-situ techniques for a full characterisation of individual micrometeoroids (flux, mass, charge, trajectory, composition) and collects and returns these samples to Earth for a detailed analysis. The opportunity to visit again the target comet of the Rosetta mission 67P/Churyumov-Gerasimeenternko, and to investigate its dusty environment six years after Rosetta with complementary methods is unique and strongly enhances and supports the scientific exploration of this target and the entire Rosetta mission. Launch opportunities are in 2020 with a backup window starting early 2026. The comet encounter occurs in September 2021 and the reentry takes place in early 2024. An encounter speed of 6 km/s ensures comparable results to the Stardust mission.