Meteorites and the physico-chemical conditions in the early solar nebula

Chondritic meteorites constitute the most ancient rock record available in the laboratory to study the formation of the solar system and its planets. Detailed investigations of their mineralogy, petrography, chemistry and isotopic composition and comparison with other primitive solar system samples such as cometary dust particles have allowed through the years to decipher the conditions of formation of their individual components thought to have once been free-floating pieces of dust and rocks in the early solar nebula. When put in the context of astrophysical models of young stellar objects, chondritic meteorites and cometary dust bring essential insights on the astrophysical conditions prevailing in the very first stages of the solar system. Several exemples are shown in this chapter, which include (1) high temperature processes and the formation of chondrules and refractory inclusions, (2) oxygen isotopes and their bearing on photochemistry and large scale geochemical reservoirs in the nebula, (3) organosynthesis and cold cloud chemistry recorded by organic matter and hydrogen isotopes, (4) irradiation of solids by flares from the young Sun and finally (5) large scale transport and mixing of material evidenced in chondritic interplanetary dust particles and samples returned from comet Wild2 by the Stardust mission.Comment: to appear in the proceedings of the Les Houches Winter School "Physics and Astrophysics of Planetary Systems", (EDP Sciences: EAS Publications Series

Evolution of oxygen isotopic composition in the inner solar nebula

Changes in the chemical and isotopic composition of the solar nebula with time are reflected in the properties of different constituents that are preserved in chondritic meteorites. CR carbonaceous chondrites are among the most primitive of all chondrite types and must have preserved solar nebula records largely unchanged. We have analyzed the oxygen and magnesium isotopes in a range of the CR constituents of different formation temperatures and ages, including refractory inclusions and chondrules of various types. The results provide new constraints on the time variation of the oxygen isotopic composition of the inner (<5 AU) solar nebula - the region where refractory inclusions and chondrules most likely formed. A chronology based on the decay of short-lived 26Al (t1/2 ~ 0.73 Ma) indicates that the inner solar nebula gas was 16O-rich when refractory inclusions formed, but less than 0.8 Ma later, gas in the inner solar nebula became 16O-poor and this state persisted at least until CR chondrules formed ~1-2 Myr later. We suggest that the inner solar nebula became 16O-poor because meter-size icy bodies, which were enriched in 17,18O due to isotopic self-shielding during the ultraviolet photo dissociation of CO in the protosolar molecular cloud or protoplanetary disk, agglomerated outside the snowline, drifted rapidly towards the Sun, and evaporated at the snowline. This led to significant enrichment in 16O-depleted water, which then spread through the inner solar system. Astronomical studies of the spatial and/or temporal variations of water abundance in protoplanetary disks may clarify these processes.Comment: 27 pages, 5 figure

Organics Captured from Comet Wild 2 by the Stardust Spacecraft

Organics found in Comet Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some are similar, but not identical, to those in interplanetary dust particles (IDPs) and carbonaceous meteorites. A new class of aromatic-poor organic material is also present. The organics are rich in O and N compared to meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than meteorites and IDPs. D and 15N suggest that some organics have an interstellar/protostellar heritage. While the variable extent of modification of these materials by impact capture is not yet fully constrained, a remarkably diverse suite of organic compounds is present and identifiable within the returned samples

A refractory inclusion returned by Stardust from comet 81P/Wild 2

Among the samples returned from comet 81P/Wild 2 by the Stardust spacecraft is a suite of particles from one impact track (Track 25) that are Ca-, Al-rich and FeO-free. We studied three particles from this track that range in size from 5.3 × 3.2 μm to

EURO-CARES - A European Sample Curation Facility for Sample Return Missions

EURO-CARES (European Curation of Astromaterials Returned from the Exploration of Space) was a three-year multinational project (2015–2017) funded by the European Commission's Horizon 2020 research programme. The objective of EURO-CARES was to create a roadmap for the implementation of a European Extra-terrestrial Sample Curation Facility (ESCF). This facility was intended to be suitable for the curation of samples from return missions from the Moon, asteroids, Mars, and other bodies of the Solar System. The EURO-CARES project covered five technical areas, led by scientists and engineers from institutions across Europe. 1. Planetary Protection: Planetary protection requirements and implementation approaches were assessed by experts and guided by international policy. Existing sterilization methods and techniques were reviewed. It was found that measures already employed for high containment biosafety facilities are suitable for a restricted sample return mission. However, the development of certain technologies, such as a ‘double walled’ isolator, remote manipulation, integration of scientific analytical instruments, etc., is also required. 2. Facilities and Infrastructure: Aspects from building design to storage of the samples were examined in the project. Requirements for the facility included that it contained a receiving laboratory, a cleaning and opening laboratory, a bio-assessment laboratory, a curation laboratory, and sample storage. Different design solutions were prepared in collaboration with architects. 3. Instruments and Methods: The methodology of characterisation of returned samples and the instrument base required at the ESCF were determined. The analyses provide an appropriate level of characterisation while ensuring minimal contamination and minimal alteration of the sample. When the samples are returned to Earth, several stages of studies would be conducted. 4. Analogue Samples: Analogue proxy samples were considered critical for testing sample handling, preparation techniques, storage conditions, planetary protection measures, as well as to validate new analytical methods. A list of useful analogue samples has been assembled. 5. Sample Transport: The Earth re-entry capsule from a sample return mission is targeted at a specific landing ellipse on Earth and must then be transported safely to the ESCF in an appropriate transport container. Lessons learned from past sample return missions show that preparations for recovery included: training of the recovery team for every possible scenario, possible temporary facilities nearby the landing site, environmental measurements and collection of samples at the landing site, added to this if necessary, would be planetary protection measures. In conclusion, long-term curation of extra-terrestrial samples requires that the samples are kept clean to minimize the risk of Earth contaminants, at the same time as contained, in case of a restricted sample return. This work describes a roadmap for a combined high containment and ultraclean European sample curation facility and the development of the necessary novel scientific and engineering methods and techniques

The Oxygen Isotopic Composition of Samples Returned from Asteroid Ryugu with Implications for the Nature of the Parent Planetesimal

We present oxygen isotopic analyses of fragments of the near-Earth C-b-type asteroid Ryugu returned by the Hayabusa2 spacecraft that reinforce the close correspondence between Ryugu and CI chondrites. Small differences between Ryugu samples and CI chondrites in Delta'O-17 can be explained at least in part by contamination of the latter by terrestrial water. The discovery that a randomly sampled C-complex asteroid is composed of CI-chondrite-like rock, combined with thermal models for formation prior to significant decay of the short-lived radioisotope Al-26, suggests that if lithified at the time of alteration, the parent body was small (50 km in radius), it was likely composed of high-permeability, poorly lithified sediment rather than consolidated rock.ISSN:2632-333

A roadmap for a European extraterrestrial sample curation facility - the EURO CARES project

Sample return missions are among the most exciting space missions, providing both scientifically unique information and an unparalleled mechanism for the inspiring the public. Returned samples allow us to make critical ground truth measurements that can calibrate remote sensing measurements from spacecraft. Some scientific studies can only be done in laboratories rather than remotely or with landed spacecraft. Currently Europe does not have a facility suitable for the curation of returned extra-terrestrial samples. This not only hinders European Space Agency (ESA) missions, but also renders European institutions and Principal Investigators unable to fully participate as equal participants in missions implemented by other countries. The EURO CARES project was the first European attempt to review and evaluate the current state-of-the-art in curatorial practice for sample return missions, and determine the different and necessary steps in order to create a fully functional European Extra-terrestrial Sample Curation Facility to match the ESA requirements.SCOPUS: ch.binfo:eu-repo/semantics/publishe

Carbonate record of temporal change in oxygen fugacity and gaseous species in asteroid Ryugu

The Hayabusa2 spacecraft explored asteroid Ryugu and brought its surface materials to Earth. Ryugu samples resemble Ivuna-type (CI) chondrites-the most chemically primitive meteorites-and contain secondary phyllosilicates and carbonates, which are indicative of aqueous alteration. Understanding the conditions (such as temperature, redox state and fluid composition) during aqueous alteration is crucial to elucidating how Ryugu evolved to its present state, but little is known about the temporal changes in these conditions. Here we show that calcium carbonate (calcite) grains in Ryugu and Ivuna samples have variable O-18/O-16 and C-13/C-12 ratios that are, respectively, 24-46 & PTSTHOUSND; and 65-108 & PTSTHOUSND; greater than terrestrial standard values, whereas those of calcium-magnesium carbonate (dolomite) grains are much more homogeneous, ranging within 31-36 & PTSTHOUSND; for oxygen and 67-75 & PTSTHOUSND; for carbon. We infer that the calcite precipitated first over a wide range of temperatures and oxygen partial pressures, and that the proportion of gaseous CO2/CO/CH4 molecules changed temporally. By contrast, the dolomite formed later in a more oxygen-rich and thus CO2-dominated environment when the system was approaching equilibrium. The characteristic isotopic compositions of secondary carbonates in Ryugu and Ivuna are not observed for other hydrous meteorites, suggesting a unique evolutionary pathway for their parent asteroid(s). The asteroid Ryugu experienced aqueous alteration under changing temperature and redox conditions, according to an isotopic analysis of secondary calcite and dolomite grains in samples from Ryugu obtained by the Hayabusa2 spacecraft

Isotopic Compositions of Comentary Matter Returned by Stardust

Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single17O-enriched circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is16O-enriched, like refractory inclusions in meteorites, suggesting that Wild 2 contains material formed at high temperature in the inner solar system and transported to the Kuiper belt before comet accretion

Isotopic compositions of cometary matter returned by Stardust

Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single O-17-enriched circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is O-16-enriched, like refractory inclusions in meteorites, suggesting that Wild 2 contains material formed at high temperature in the inner solar system and transported to the Kuiper belt before comet accretion