The Creston, California, Meteorite Fall and the Origin of L Chondrites
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Meteoritics & Planetary Science 1–22 (2019) doi: 10.1111/maps.13235 The Creston, California, meteorite fall and the origin of L chondrites Peter JENNISKENS 1,2*, Jason UTAS 3, Qing-Zhu YIN 4, Robert D. MATSON5, Marc FRIES 6, J. Andreas HOWELL 7, Dwayne FREE 7, Jim ALBERS1, Hadrien DEVILLEPOIX 8, Phil BLAND 8, Aaron MILLER9, Robert VERISH10, Laurence A. J. GARVIE 11, Michael E. ZOLENSKY 6, Karen ZIEGLER 12, Matthew E. SANBORN 4, Kenneth L. VEROSUB4, Douglas J. ROWLAND 13, Daniel R. OSTROWSKI 2,14, Kathryn BRYSON 2,14, Matthias LAUBENSTEIN 15, Qin ZHOU 16, Qiu-Li LI 17, Xian-Hua LI 17, Yu LIU 17, Guo-Qiang TANG 17, Kees WELTEN 18, Marc W. CAFFEE19, Matthias M. M. MEIER 20, Amy A. PLANT 20, Colin MADEN 20, Henner BUSEMANN 20, Mikael GRANVIK 21,22 (The Creston Meteorite Consortium) 1SETI Institute, Carl Sagan Center, Mountain View, California 94043, USA 2NASA Ames Research Center, Moffett Field, California 94035, USA 3Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, California 90095, USA 4Department of Earth and Planetary Sciences, University of California at Davis, Davis, California 95616, USA 5Leidos, Seal Beach, California 90740, USA 6Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, Texas 77058, USA 7Spalding Allsky Camera Network, SkySentinel, LLC (SSL), Melbourne, Florida 32940, USA 8Faculty of Science & Engineering, Curtin University, Bentley, Perth, Western Australia 6102, Australia 9Ancient Earth Trading Co., Atascadero, California 93423, USA 10Meteorite Recovery Lab, Escondido, California 92046, USA 11Center for Meteorite Studies, School of Earth & Space Exploration, Arizona State University, Tempe, Arizona 85287, USA 12Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico 87131, USA 13Center for Molecular and Genomic Imaging, Department of Biomedical Engineering, UC Davis, Davis, California 95616, USA 14Bay Area Environmental Research Institute, 625 2nd St., Suite 209, Petaluma, California 94952,USA 15Ist. Naz. di Fiscia Nucleare, Lab. Naz. del Gran Sasso, I-67100 Assergi (AQ), Italy 16National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China 17State Key Laboratory of Lithospheric Evolution, Inst. Geol. and Geophys., Chinese Acad. Sci., Beijing 100029, China 18Space Sciences Laboratory, University of California, Berkeley, California 94720, USA 19PRIME Laboratory, Purdue University, West Lafayette, Indiana 47907, USA 20Institute of Geochemistry and Petrology, ETH Zurich,€ CH-8092, Zurich,€ Switzerland 21University of Helsinki, Department of Physics, FI-00014, Helsinki, Finland 22Lulea University of Technology, Division of Space Technology, S-98128 Kiruna, Sweden *Corresponding author. E-mail: [email protected] (Received 11 April 2018; revision accepted 19 November 2018) Abstract–It hasbeenproposedthatallLchondritesresultedfromanongoingcollisionalcascadeof fragments that originated from the formation of the ~500 Ma 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 chondritefallatCreston,CA(herereclassifiedtoL5/6).Creston’sshort1.30 Æ 0.02AUsemimajor 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 40–50 Ma. However, Creston’s small [Correction added on 7th March 2019, after first online publication: affiliation 5 was changed from “Leidos, Seal Beach, San Diego, California, 90704, USA” to “Leidos, Seal Beach, California 90740, USA”] 1 © The Meteoritical Society, 2019. 2 P. Jenniskens et al. meteoroid size and low 4.23 Æ 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 m6 resonance. The U-Pb systematics of Creston apatite reveals a Pb-Pb age of 4,497.1 Æ 3.7 Ma, and an upper intercept U-Pb age of 4,496.7 Æ 5.8 Ma (2r), circa 70 Ma after formation of CAI, as found for other L chondrites. The K-Ar (age ~4.3 Ga) and U,Th-He (age ~1 Ga) chronometers were not reset at ~500 Ma, while the lower intercept U-Pb age is poorly defined as 770 Æ 320 Ma. So far, the three known L chondrites that impacted on orbits with semimajoraxesa<2.0AUallhavehigh(>3 Ga)K-Arages.ThisarguesforasourceofsomeofourL chondrites in the inner Main Belt. Not all L chondrites originate in a continuous population of Gefionfamilydebrisstretchingacrossthe3:1mean-motionresonance. INTRODUCTION Vernazza et al. 2014). Also, the current asteroid population is mostly composed of reassembled matter from large-scale There is an ongoing effort to identify the source of L disruptions of an earlier generation of planetesimals chondrites in the asteroid belt. The delivery resonance (Bottke et al. 2005). If so, the L chondrite parent body may and inclination of the source region can be identified in a have broken into several daughter asteroids during an statistical sense from meteorite falls for which an initial disruption of the L chondrite parent body long ago, atmospheric impact trajectory and pre-atmospheric orbit each of which could later have created an asteroid family in are calculated (Jenniskens 2014). So far, five L5 and L6 a different part of the Main Belt. chondrites have yielded pre-impact orbits: Innisfree, More than one recent collision created the Jesenice, Park Forest, Villalbeto de la Pena,~ and Novato. meteoroids that now impact Earth. L5 and L6 About two-thirds of L chondrites have a common chondrites have a broad distribution of cosmic ray 470 Æ 6 Ma Ar-Ar and U-Pb resetting age, especially exposure ages (CRE). The CRE age identifies the those that show shock blackening (Anders 1964; Haack moment in time when a collision caused the meteoroid et al. 1996; Alexeev 1998; Scott 2002; Korochantseva to no longer be shielded from cosmic rays by a few et al. 2007; Weirich et al. 2012; Yin et al. 2014; Li and meters of overlaying burden. The broad distribution Hsu 2016; Wu and Hsu 2017). In addition, L chondrite implies that multiple disruptive collision or cratering falls were much more common 470 Ma ago, where they events produced this meteorite type (Marti and Graf are found in the fossil record of terrestrial strata dated 1992; Eugster et al. 2006; Wasson 2012). Note that L3 to 467.3 Æ 1.6 Ma (Schmitz et al. 2001, 2016). and L4 chondrites appear to have different CRE age It has been proposed that the Gefion asteroid family, distributions than L5 or L6 chondrites, and are not located near the 5:2 mean-motion resonance, was formed considered here. At this moment, there are no observed at that time and this is the source of these shocked L L3 or L4 falls with measured pre-atmospheric orbits. chondrites (Nesvorny et al. 2009). While delivery was Here, we report on the October 24, 2015 fall of the rapid, initially, via the 5:2 mean-motion resonance, the ordinary chondrite Creston near Paso Robles, California. meteorites would now be delivered to Earth more Two hundred and eighteen eyewitnesses reported the efficiently via the 3:1 mean-motion resonance. Gefion is fireball (American Meteor Society event number 2635- the only known family with large members of L (as 2015). Fourteen witnesses close to the path heard opposed to H and LL) chondrite composition (Vernazza sonic booms shortly after the fireball. Seismic stations et al. 2014) and some asteroids found in the 3:1 mean- timed tremors when the shock wave coupled to the motion resonance, e.g., (355) Gabriella, (14470) Utra, ground. Based on the visual and seismic sightings, six and (1722) Goffin, have L chondrite-like spectra (Fieber- Doppler radar returns from the United States National Beyer and Gaffey 2015). In more recent years, however, Oceanic and Atmospheric Administration (NOAA) next the reflection spectra of some Gefion family members generation weather radar network (NEXRAD) were were found to resemble that of H chondrites and basaltic identified that were likely from falling meteorites (Fries achondrites (McGraw et al. 2017) and the age of et al. 2016). Based on the radar-defined search area, the the Gefion family may be older than required, first stone was located on October 27, now named CR01 1103 Æ 386 Ma according to Spoto et al. (2015), who and classified as an L6 ordinary chondrite (Bouvier et al. did not include the initial velocity at ejection, however. 2017). The stone had shattered when it hit a metal fence There could be more than one source region of L post. Five other meteorites were found in the following chondrites in the main asteroid belt. It has been argued month, with a total weight of 852.3 g (Table 1). that large groups of compositionally similar asteroids are a Two of the meteorites (CR05 and CR06) were made natural outcome of planetesimal formation (Youdin 2011; available for nondestructive analysis (Fig. 1), while The Creston, California, meteorite fall 3 Table 1. Creston meteorite masses and find locations. CR# Date of find Mass (g) Latitude (N) Longitude (W) Altitude (m) Finder 01b October 27, 2015 ~396a 35.57508 120.49847 397 Robert & Ann Marie Ward 02b October 28, 2015 69.2 ~35.568 ~120.481 ~499 Terry Scott 03 October 31, 2015 102.2 ~35.568 ~120.481 ~499 Terry Scott 04 November 16, 2015 108 ~35.568 ~120.481 ~499 Michael Farmer 05b November 19, 2015 72.681 ~35.565 ~120.467 ~477 (local finder/via Sonny Clary) 06b November 21, 2015 95.549 35.56547 120.46747 477 Aaron Miller aBroken on impact. bMeteorites studied here. Fig. 1. Top) Optical photographs of Creston meteorites #5 (left) and #6. Notice how each meteorite has one side that is more reddish colored, the irregular surface in the case of C05 and the fresher flatter surface in the case of C06, respectively.