The Aguas Zarcas breccia - similarities to surface features of C-type asteroids Ryugu and Bennu
Imene Kerraouch1,2, Michael E. Zolensky2 Addi Bischoff1
1
Institut für Planetologie, University of Münster, Wilhelm-Klemm Str. 10, D-48149 Münster, Germany.
2Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston TX 77058, USA(ikerraou@uni-muenster.de)
Knowledge of the materials originally present in the protosolar nebula is one of the most significant constraints for models ofthe formation of our solar system. The physicochemical properties of these original materials can be determined through two
different and complementary approaches: (a) astronomical observations of nascent stellar systems and the dense clouds fromwhich they originated and (b) laboratory studies of available astromaterials such as meteorites, interplanetary dust particles,
comet coma grains, including returned mission samples (e.g., from Hayabusa -1 -2; OSIRIS-Rex). Laboratory study of these
extraterrestrial materials provides valuable information about the first solid materials of the early solar system and theirevolution. Here, we present petrographic and mineralogical characteristics of work on the polymict carbonaceous breccia
Aguas Zarcas [1].
On April 23, 2019, at 21:07 local time, a meteorite fall occurred in Aguas Zarcas, San Carlos County, Alajuela province, Costa
Rica. The rapid recovery of this brecciated carbonaceous chondrite after its fall provides an opportunity to investigate a freshly
fallen, relatively uncontaminated, and highly-brecciated meteorite to compare with samples returned by the Hayabusa2 andOSIRIS-REx spacecraft from C-complex asteroids.
This study includes the examination of several pre-rain fragments. X-ray computed tomography (XCT) results show numerous
different lithologies [1]. In this study, we describe the petrography and mineralogy of five different lithologies of the Aguas
Zarcas meteorite. We also present data on the bulk oxygen isotopes of some of these lithologies. We describe all fragments indetail and attempt a classification of each lithology in order to better understand tfhe origin and formation history of the Aguas
Zarcas parent body.
Our results show that some lithologies of Aguas Zarcas are similar to those in CM chondrites, but others are unique. The
different lithologies [1] also represent different degrees of hydration and heating, which are good analogues for the types ofmaterial returned from asteroids Bennu and Ryugu.
Spectroscopic observations of Ryugu and Bennus compared to laboratory measurements of meteorites suggest that theasteroids have some similarities to heated CM, heated CI, or CI chondrites [2-5]. Both asteroids are thought to be composed ofmaterials altered by aqueous alteration (e.g., [5]) and formed by reaccretion after destruction by impacts and brecciation (e.g.,[6-7]). Considering the different lithologies in Aguas Zarcas [2] and other CM chondrites [8-9], these types of carbonaceouschondrites can be considered good analogues for samples from Ryugu and Bennu. The presence of unique and rare lithologies
in Aguas Zarcas, different from typical CM chondrite lithologies, requires complex mixing of different materials in a highly
dynamic environment.
Fig.1: Left image: sample catcher chamber A
from Hayabusa2, captured by an optical
microscope, shows many particles larger than 1mm (Photo by JAXA Dec. 24, 2021). The rightimage:

XCT image of a sample of Aguas

Zarcas, showing a dark homogeneous C1-clast(marked by a circle) (Kerraouch et al., 2021;2022). Both materials exhibit a mixture ofdifferent lithologies resulting from impact
fragmentation, mixing, and reaccretion during
the evolution of their parent bodies.

References [1] Kerraouch et al., 2021. Meteoritics & Planet. Sci. 56, 277-310; [2] Kitazato et al., 2019. Science 364, 272–275;[3] Matsuoka et al., 2015. Icarus 254. 135–143; [4] Hanna et al., 2019. LPI abstract #2029; [5] Hamilton et al., 2019. NatureAstronomy. 3.332–340; [6] McCoy et al., 2019. Metsoc54 abstract #6428; [7] Michel et al., 2020. Nature 11, 2655; [8]Kerraouch et al., 2019. Chemie der Erde 79, 125518; [9] Lentfort et al., 2020. Meteoritics & Planetary Sci. 56, 127-147.