¹Megan Broussardet al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.701381]
¹Department of Earth, Environmental, and Planetary Sciences and the McDonnell Center for the Space Sciences,Washington University in St. Louis, St. Louis, Missouri, USA
Published by arrangement with John Wiley & Sons

CI chondrites are a compositionally primitive group of meteorites that haveundergone extensive aqueous alteration, providing insights into the evolution of primitiveplanetesimals. Oued Chebeika 002 is the most pristine CI chondrite to date. In this work,we report its mineralogy, bulk chemistry, oxygen and potassium isotope ratios, andcosmogenic radionuclides 10 Be, 26 Al, and 36 Cl. The 10 Be cosmic ray exposure ages of OuedChebeika 002 samples are 2.6 0.5 and 2.9 0.7 Myr. The d41 K of two samples is0.114 0.019 and 0.247 0.044 &. We find that the mineralogy, oxygen isotopes,potassium isotopes, and bulk chemistry of Oued Chebeika 002 overlap with those ofsamples returned from the asteroids Ryugu and Bennu. We therefore propose that CI chondrites and the asteroids Bennu and Ryugu may have originated from a common parentbody, for which we propose the name “Naunet,” after an Egyptian goddess of primordialwater. Naunet formed in the outer solar system and underwent aqueous alteration. In themain belt, Naunet broke up, producing rubble-pile asteroids, including Bennu, Ryugu, andthe secondary CI chondrite parent body/bodies, fragments of which survived passage to theEarth’s surface, becoming CI chondrites.

¹Tetsuya Yokoyama et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.701411]
¹Department of Earth & Planetary Sciences, Institute of Science Tokyo, Meguro, Japan
Published by arrangement with John Wiley & Sons

Sample return missions play a significant role in planetary science by providing
pristine extraterrestrial materials. JAXA’s Hayabusa2 and NASA’s OSIRIS-REx missions
have returned samples from the C-type asteroids Ryugu and Bennu, respectively. The
chemical and mineralogical compositions of these samples closely resemble those of CI
chondrites, the traditional reference material for solar system abundances. Based on the
findings of the Hayabusa2 mission, JAXA launched the Ryugu Reference Project (RRP) to
maximize the scientific value of the returned samples and formed the RRP Measurement
Definition Team (RRP-MDT) to elucidate the RRP’s scientific goal and objectives. The
RRP-MDT defined the goal of RRP to reassess the elemental abundances and isotopic
compositions of the solar system through comprehensive analyses of the returned asteroid
samples and CI chondrites. To this end, the team recommended preparing homogeneously
powdered Ryugu reference materials (RRM) using approximately 750 and 400mg of
samples from Chambers A and C, respectively, to address observed compositional
heterogeneities. The team proposed to measure the elemental abundances and isotopic
compositions of the RRM by analytical techniques involving seven specific measurement
groups. Through comprehensive analytical methodologies, interlaboratory calibration, and
statistical evaluation, the RRP aims to refine our understanding of solar system formation
and evolution