Suchergebnisse

###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). --

Haumea—one of the four known trans-Neptunian dwarf planets—is a very elongated and rapidly rotating body1, 2, 3. In contrast to other dwarf planets4, 5, 6, its size, shape, albedo and density are not well constrained. The Centaur Chariklo was the first body other than a giant planet known to have a ring system7, and the Centaur Chiron was later found to possess something similar to Chariklo's rings8, 9. Here we report observations from multiple Earth-based observatories of Haumea passing in front of a distant star (a multi-chord stellar occultation). Secondary events observed around the main body of Haumea are consistent with the presence of a ring with an opacity of 0.5, width of 70 kilometres and radius of about 2,287 kilometres. The ring is coplanar with both Haumea's equator and the orbit of its satellite Hi'iaka. The radius of the ring places it close to the 3:1 mean-motion resonance with Haumea's spin period—that is, Haumea rotates three times on its axis in the time that a ring particle completes one revolution. The occultation by the main body provides an instantaneous elliptical projected shape with axes of about 1,704 kilometres and 1,138 kilometres. Combined with rotational light curves, the occultation constrains the three-dimensional orientation of Haumea and its triaxial shape, which is inconsistent with a homogeneous body in hydrostatic equilibrium. Haumea's largest axis is at least 2,322 kilometres, larger than previously thought, implying an upper limit for its density of 1,885 kilograms per cubic metre and a geometric albedo of 0.51, both smaller than previous estimates1, 10, 11. In addition, this estimate of the density of Haumea is closer to that of Pluto than are previous estimates, in line with expectations. No global nitrogen- or methane-dominated atmosphere was detected. ; J.L.O. acknowledges funding from Spanish and Andalusian grants MINECO AYA-2014-56637-C2-1-P and J. A. 2012-FQM1776 as well as FEDER funds. Part of the research leading to these results received funding from the European Union's Horizon 2020 Research and Innovation Programme, under grant agreement no. 687378. B.S. acknowledges support from the French grants 'Beyond Neptune' ANR-08-BLAN-0177 and 'Beyond Neptune II' ANR-11-IS56-0002. Part of the research leading to these results has received funding from the European Research Council under the European Community's H2020 (2014-2020/ERC grant agreement no. 669416 'Lucky Star'). A.P. and R.S. have been supported by the grant LP2012-31 of the Hungarian Academy of Sciences. All of the Hungarian contributors acknowledge the partial support from K-125015 grant of the National Research, Development and Innovation Office (NKFIH). G.B.-R., F.B.-R., F.L.R., R.V.-M., J.I.B.C., M.A., A.R.G.-J. and B.E.M. acknowledge support from CAPES, CNPq and FAPERJ. J.C.G. acknowledges funding from AYA2015-63939-C2-2-P and from the Generalitat Valenciana PROMETEOII/2014/057. K.H. and P.P. were supported by the project RVO:67985815. The Astronomical Observatory of the Autonomous Region of the Aosta Valley acknowledges a Shoemaker NEO Grant 2013 from The Planetary Society. We acknowledge funds from a 2016 'Research and Education' grant from Fondazione CRT. We also acknowledge the Slovakian project ITMS no. 26220120029.