¹Martin R. LEE,¹Cameron FLOYD,¹Pierre-Etienne MARTIN,²Xuchao ² A. FRANCHI,¹Laura JENKINS,¹Sammy GRIFFIN
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13978]
¹School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK2School of Physical
²Sciences, Open University, Milton Keynes MK7 6AA, UK*Corresponding author.Martin R. Lee, School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK
Published by arrangement with John Wiley & Sons

LaPaz Icefield (LAP) 02239 is a mildly aqueously altered CM2 carbonaceouschondrite that hosts a xenolith from a primitive chondritic parent body. The xenolithcontains chondrules and calcium- and aluminum-rich inclusions (CAIs) in a very fine-grained matrix. The chondrules are comparable in mineralogy and oxygen isotopiccomposition with those in the CMs, and its CAIs are also mineralogically similar to the CMpopulation apart for being unusually small and abundant. The presence of serpentinedemonstrates that the xenolith has been aqueously altered, and its phyllosilicate-rich matrixhas a comparable oxygen isotopic composition to the matrices of CM meteorites. Thexenolith’s chondrules lack fine-grained rims, whereas the xenolith itself has a fine-grainedrim that is petrographically and chemically comparable with the rims on coarse grainedobjects in LAP 02239 and other CM meteorites. These properties show that the xenolith’sparent body was formed from similar materials to the CM parent body(ies). Following itslithification by aqueous alteration, a piece of the xenolith’s parent body was impact-ejected,acquired a fine-grained rim while free-floating in the protoplanetary disc, then was accretedalong with rimmed chondrules and other materials to make the LAP 02239 parent body.Subsequent aqueous processing of the LAP 02239 parent body altered the fine-grained rimson the xenolith, chondrules, and CAIs. The xenolith shows that the timespan of geologicalevolution of carbonaceous chondrite parent bodies was sufficiently long for some of them tohave been aqueously altered before others had formed.INTRODUCTIONThe Mighei-like (CM) carbonaceous chondrite (CC)meteorites have close spectroscopic affinities to C-complexasteroids (Burbine,2016) and so likely sample one or moreof them. The parent body(ies) of the CMs were formed bythe accretion of relatively coarse-grained objects (i.e.,chondrules and calcium- and aluminum-rich inclusions[CAIs]) together with fine-grained material that formsthe enclosing matrix (Barber,1981; McSween Jr. &Richardson,1977). The chondrules and other coarse-grainedobjects typically have fine-grained rims that they acquiredwhile free-floating in the protoplanetary disc (Hanna &Ketcham,2018; Metzler et al.,1992). The constituents of thecoarse-grained objects, fine-grained rims and matrix(anhydrous silicates, metal, sulfides, oxides, and amorphousmaterials) were partially to completely altered by parentbody aqueous activity at~4563 Ma (Bunch & Chang,1980;Fujiya et al.,2012; McSween Jr.,1979a,1979b). Theresultant secondary minerals are volumetrically dominatedby phyllosilicates that are intergrown with carbonates,oxides, and sulfides (Barber,1981; Bunch & Chang,1980;Fuchs et al.,1973;Howardetal.,2009,2011,2015;Leeet al.,2014; Tomeoka & Buseck,1985;Trigo-Rodrıguezet al.,2019; Zolensky et al.,1993).TheCMsareclassifiedby petrologic type/subtype using various properties thatMeteoritics & Planetary Science1–16 (2023)doi: 10.1111/maps.139781Ó2023 The Authors.Meteoritics & Planetary Sciencepublished by Wiley Periodicals LLC on behalf of The Meteoritical Society.This is an open access article under the terms of theCreative Commons AttributionLicense, which permits use,distribution and reproduction in any medium, provided the original work is properly cited.

¹K.Righter et al.(>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13973]
¹NASA Johnson Space Center, Houston, Texas, USA
Published by arrangement with John Wiley & Sons

NASA’s OSIRIS-REx spacecraft collected samples from carbonaceous near-Earth asteroid (101955) Bennu on October 20, 2020, and will deliver them to the Earth on September 24, 2023. The samples will be processed at the NASA Johnson Space Center (JSC), where most of the sample collection will be subsequently curated in a new cleanroom suite. The spacecraft collected loose regolith two ways: in a bulk sample chamber capable of holding up to 2 kg, and on industrial Velcro “contact pads” intended to collect small particles at the surface. Included in the JSC collection will be the bulk sample, the contact pads, contamination-monitoring witness plates, and supporting hardware. Planning for the curation of the samples and hardware started at the earliest phase of proposal development and continued in parallel with project development and execution. Because a major mission goal is characterization of organic compounds in the Bennu samples, extra effort was spent in the design stage to ensure a clean curation environment. Here, we describe the preparations to receive the sample, including the design, construction, outfitting, and monitoring of the cleanrooms at JSC; the planned recovery of the sample-containing capsule when it lands on Earth; and the approach to characterizing and cataloging the samples. These curation efforts will result in the distribution of pristine Bennu samples from JSC to the OSIRIS-REx science team, international partners, and the global scientific community for years to come.