Explore the vast range of titles available.

Asteroidal and cometary fragments have been indicated as possible sources of the building blocks of life for the early Earth. Samples returned from the asteroid Ryugu are uncontaminated and contain organic matter. Such samples enable an investigation of the processes that formed and altered extraterrestrial organic matter. Here, the FTIR and Raman responses of insoluble organic matter (IOM) isolated from Ryugu particles and carbonaceous chondrites are reported. Several relationships were observed: (1) a strong positive correlation of CH2/CH3 plotted against aliphatics/C=C; (2) a strong negative correlation of CH2/CH3 plotted against δ15N and δ13C; and (3) strong negative correlations of FTIR band ratios plotted against Raman band parameters and D/G values. The data are not consistent with even moderate heating of the IOM, as indicated by CH2/CH3 ratios that are consistent with unheated carbonaceous chondrites. The C and N isotope data previously collected for each Ryugu particle preclude aqueous alteration based on our understanding of its effects on carbonaceous chondrite IOM. Mixing of several IOM endmembers was considered, but due to the similarities of the particle with the lowest CH2/CH3 ratio to the other particles in terms of its other spectroscopic parameters, this scenario was considered unlikely. Finally, the effects of irradiation were considered, and UV irradiation, in particular, was hypothesised to be the best explanation for the trends observed. Overall, the data highlight the importance of comprehensive data sets for revealing extraterrestrial processes, which could define the nature of organic matter reaching habitable environments, such as those of the Early Earth.

All life on Earth contains amino acids and carbonaceous chondrite meteorites have been suggested as their source at the origin of life on Earth. While many meteoritic amino acids are considered indigenous, deciphering the extent of terrestrial contamination remains an issue. The Ryugu asteroid fragments (JAXA Hayabusa2 mission), represent the most uncontaminated primitive extraterrestrial material available. Here, the concentrations of amino acids from two particles from different touchdown sites (TD1 and TD2) are reported. The concentrations show that N,N-dimethylglycine (DMG) is the most abundant amino acid in the TD1 particle, but below detection limit in the other. The TD1 particle mineral components indicate it experienced more aqueous alteration. Furthermore, the relationships between the amino acids and the geochemistry suggest that DMG formed on the Ryugu progenitor body during aqueous alteration. The findings highlight the importance of aqueous chemistry for defining the ultimate concentrations of amino acids in primitive extraterrestrial samples. Amino acid concentrations from 2 particles returned from different touchdown sites on the surface of Ryugu are reported. Differences in chemistry suggest different levels of aqueous alteration are recorded at the 2 sampled locations.

The pursuit of understanding the origins of life (OoL) on and off Earth and the search for extraterrestrial life (ET) are central aspects of astrobiology. Despite the considerable efforts in both areas, more novel and multifaceted approaches are needed to address these profound questions with greater detail and with certainty. The complexity of the chemical milieu within ancient geological environments presents a diverse landscape where biomolecules and non-biomolecules interact. This interaction could lead to life as we know it, dominated by biomolecules, or to alternative forms of life where non-biomolecules could play a pivotal role. Such alternative forms of life could be found beyond Earth, i.e., on exoplanets and the moons of Jupiter and Saturn. Challenging the notion that all life, including ET life, must use the same building blocks as life on Earth, the concept of contingency—when expanded beyond its macroevolution interpretation—suggests that non-biomolecules may have played essential roles at the OoL. Here, we review the possible role of contingency and non-biomolecules at the OoL and synthesize a conceptual model formally linking contingency with non-biomolecular OoL theories. This model emphasizes the significance of considering the role of non-biomolecules both at the OoL on Earth or beyond, as well as their potential as agnostic biosignatures indicative of ET Life.

The analysis of samples returned from the C-type asteroid Ryugu has drastically advanced our knowledge of the evolution of early solar system materials. However, no consensus has been obtained on the chronological data, which is important for understanding the evolution of the asteroid Ryugu. Here, the aqueous alteration age of Ryugu particles was determined by the Mn–Cr method using bulk samples, yielding an age of 4.13 + 0.62/−0.55 Myr after the formation of Ca–Al-rich inclusions (CAI). The age corresponds to 4563.17 + 0.60/−0.67 Myr ago. The higher 55Mn/52Cr, ε 54Cr, and initial ε 53Cr values of the Ryugu samples relative to any carbonaceous chondrite samples implies that its progenitor body formed from the least thermally processed precursors in the outermost region of the protoplanetary disk. Despite accreting at different distances from the Sun, the hydrous asteroids (Ryugu and the parent bodies of CI, CM, CR, and ungrouped C2 meteorites) underwent aqueous alteration during a period of limited duration (3.8 ± 1.8 Myr after CAI). These ages are identical to the crystallization age of the carbonaceous achondirtes NWA 6704/6693 within the error. The ε 54Cr and initial ε 53Cr values of Ryugu and NWA 6704/6693 are also identical, while they show distinct Δ'17O values. This suggests that the precursors that formed the progenitor bodies of Ryugu and NWA 6703/6693 were formed in close proximity and experienced a similar degree of thermal processing in the protosolar nebula. However, the progenitor body of Ryugu was formed by a higher ice/dust ratio, than NWA6703/6693, in the outer region of the protoplanetary disk.

Background Asbestos is a fibrous mineral that was widely used in the past. However, asbestos inhalation is associated with an aggressive type of cancer known as malignant mesothelioma (MM). After inhalation, an iron-rich coat forms around the asbestos fibres, together the coat and fibre are termed an “asbestos ferruginous body” (AFB). AFBs are the main features associated with asbestos-induced MM. Whilst several studies have investigated the external morphology of AFBs, none have characterised the internal morphology. Here, cross-sections of multiple AFBs from two smokers and two non-smokers are compared to investigate the effects of smoking on the onset and growth of AFBs. Morphological and chemical observations of AFBs were undertaken by transmission electron microscopy, energy dispersive x-ray spectroscopy and selected area diffraction. Results The AFBs of all patients were composed of concentric layers of 2-line or 6-line ferrihydrite, with small spherical features being observed on the outside of the AFBs and within the cross-sections. The spherical components are of a similar size to Fe-rich inclusions found within macrophages from mice injected with asbestos fibres in a previous study. As such, the spherical components composing the AFBs may result from the deposition of Fe-rich inclusions during frustrated phagocytosis. The AFBs were also variable in terms of their Fe, P and Ca abundances, with some layers recording higher Fe concentrations (dense layers), whilst others lower Fe concentrations (porous layers). Furthermore, smokers were found to have smaller and overall denser AFBs than non-smokers. Conclusions The AFBs of smokers and non-smokers show differences in their morphology, indicating they grew in lung environments that experienced disparate conditions. Both the asbestos fibres of smokers and non-smokers were likely subjected to frustrated phagocytosis and accreted mucopolysaccharides, resulting in Fe accumulation and AFB formation. However, smokers’ AFBs experienced a more uniform Fe-supply within the lung environment compared to non-smokers, likely due to Fe complexation from cigarette smoke, yielding denser, smaller and more Fe-rich AFBs. Moreover, the lack of any non-ferrihydrite Fe phases in the AFBs may indicate that the ferritin shell was intact, and that ROS may not be the main driver for the onset of MM.

The Hayabusa2 mission was tasked with returning samples from the C-complex asteroid Ryugu (1999 JU3), in order to shed light on the formation, evolution and composition of such asteroids. One of the main science objectives was to understand whether such bodies could have supplied the organic matter required for the origin of life on Earth. Here, a review of the studies concerning the organic matter within the Ryugu samples is presented. This review will inform the reader about the Hayabusa2 mission, the nature of the organic matter analyzed and the various interpretations concerning the analytical findings including those concerning the origin and evolution of organic matter from Ryugu. Finally, the review puts the findings and individual interpretations in the context of the current theories surrounding the formation and evolution of Ryugu. Overall, the summary provided here will help to inform those operating in a wide range of interdisciplinary fields, including planetary science, astrobiology, the origin of life and astronomy, about the most recent developments concerning the organic matter in the Ryugu return samples and their relevance to understanding our solar system and beyond. The review also outlines the issues that still remain to be solved and highlights potential areas for future work.

Enstatite chondrites have been regarded as major building blocks of the Earth and other differentiated inner planetary bodies due to the similarity of Δ17O (deviation of the δ 17O value from the terrestrial silicate fractionation line) and nucleosynthetic isotope anomalies. However, this hypothesis has been rebutted by the fact that the Earth and enstatite chondrites show distinct Si isotopic compositions. It has been debated whether the origin of this Si isotope difference is the result of nebular or planetary processes. Here we show that the δ 30Si (deviation of 30Si/28Si relative to NBS 28 standard) and the Δ17O values of chondrules in unequilibrated enstatite chondrites are between −0.20‰ and −0.54‰ and −0.36‰ and +0.26‰, respectively. Furthermore, the chondrules with higher Δ17O values tend to have lower δ 30Si. The data exhibit values consistent with most of the noncarbonaceous group differentiated planetary bodies. This consistency suggests that the Si and O isotopic compositions of enstatite chondrules record those of the major precursors that formed the differentiated planetary bodies in the inner solar system. Model calculations based on the results reveal that the Si and O isotope variations of the enstatite chondrite chondrules were generated by an interaction between the evaporation-driven SiO-rich gas and partially or fully melted forsterite-rich precursor chondrules. The Mg/Si of the evaporated dust-gas mixtures increased with increasing silicate/metal ratio in the evaporated dust, which may have increased the bulk Mg/Si and δ 30Si value of the inner planetary bodies.

The Hayabusa2 mission returned primitive samples from the C-type asteroid Ryugu to Earth. The C-type asteroids hold clues to the origin of Earth’s water and the building blocks of life. The rubble pile structure of C-type asteroids is a crucial physical feature relating to their origin and evolution. A rubble pile asteroid is hypothesized to be bound primarily by self-gravity with a significant void space among irregularly shaped materials after catastrophic impacts between larger asteroids. However, the geological observations from Hayabusa2 and the analyses of the returned sample from Ryugu revealed that the high microporosity was common to various >10 m- to mm-sized materials of Ryugu, which suggests that the asteroid Ryugu is not just a loosely bound agglomeration of massive rocky debris from shattered asteroids. For a better understanding of the origin and evolution of the rubble pile asteroid, the current most accepted hypothesis should be verified by observations and laboratory analyses and improved upon based on this information. Here, the previous models are examined using Hayabusa2’s geological observations of the asteroid and the analytical data from the samples returned from Ryugu’s surface and subsurface material. Incorporating the new findings, a hypothesis for the evolution of the rubble pile asteroid Ryugu from a cometary nucleus through sublimation and subsequent dynamic resurfacing is proposed. The proposed hypothesis is applicable to other rubble-pile asteroids and would provide perspectives for near-Earth objects in general.

The Japanese Hayabusa2 spacecraft returned samples from the asteroid Ryugu in December 2020, and several results on the properties of the particles have been published since. A detailed geochemical analysis determined that the total organic carbon abundance of the sample was on average 2.92 wt%. This value is much less than the 14.6–59.3 vol% estimated from remote-sensing data for Ryugu coupled with the albedos of irradiated meteorites and organic matter. Understanding the reasons for this discrepancy is paramount to accurately predict the composition of C-complex asteroids. Here we explore several factors that may affect the estimates of organic matter abundance made using remote-sensing data. Such factors include the distribution of organic matter, the porosity and roughness of the surfaces of asteroids, and inconsistencies between the observation geometries used by remote-sensing and laboratory investigations. We posit that discussing such factors may fuel further experimental investigations of the effects of irradiation on asteroid surfaces and, thus, improve predictions of their organic composition. The differences between the estimated and measured organic matter abundances of asteroid Ryugu may result from variations in the superficial organic matter distribution, porosity of the asteroid’s surface or the observation geometries used in such studies.

Meteoritic organic matter has been studied widely, especially the solvent soluble or free organic matter (FOM) fraction. However, the different components that make up the insoluble or macromolecular organic matter (MOM) fraction have drawn little attention, with most studies focussed on the overall nature of this organic polymer. The current study has employed a series of analytical techniques, gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared (FTIR) and Raman spectroscopy, in conjunction with chemical degradation and high pressure procedures, in order to probe the nature of the MOM and FOM fractions of the CM2 chondrites: Murchison and Mighei. GC-MS has revealed that the FOM fraction is easily contaminated by microbial activity, but that there are a considerable variety of pyranone related compounds and aromatic acids that are likely indigenous. FTIR spectroscopic mapping of the FOM and MOM fractions supports the strong relationship between meteoritic organic matter and phyllosilicates, consistent with the generation of portions of meteorite organic matter, including many FOM and some LOM compounds, via aqueous alteration. Ratios of CH2 to CH3 calculated for asymmetric stretching indicate that Murchison has shorter chain length and/or more highly branched aliphatic compounds than Mighei. Petrographic studies indicate a higher degree of aqueous alteration for Mighei than Murchison and this suggests that the CH2/CH3 ratios might be explained by some degradation of the aromatic rings during aqueous alteration, which could generate the longer aliphatic chains and increase the CH2/CH3 ratio of Mighei compared to Murchison. The inverse relationship between the ratio of phyllosilicates to anhydrous silicates and silicate Si-O stretching to carboxyl hydroxyl stretching indicate the Murchison parent body accreted with or synthesised a higher abundance of carboxyl rich organic matter than that of Mighei. The refractory organic matter (ROM) component of MOM, which is isolated after chemical degradation, demonstrates a statistical similarity between both meteorites in FTIR and Raman spectroscopy; an observation that suggests a common organic progenitor may have been accreted by all CM chondrites and possibly all carbonaceous chondrites. Pressure is an important, but often neglected parameter relating to the origin of meteoritic organic matter. Model compounds, representing the oxygen and aromatic containing functionalities of MOM, have revealed the importance of intermolecular hydrogen bonding under pressure. Hydrogen bonding has been observed to facilitate esterification and is a plausible process by which portions of MOM could be generated.