Emergence of Optical Activity and Surface Morphology Changes in Racemic Amino Acid Films Under Circularly Polarized Lyman-α Light Irradiation.

The homochirality of life remains one of the most enigmatic issues in the study of the origin of life. A proposed mechanism for symmetry breaking involves irradiation by circularly polarized light (CPL). To investigate the photoreaction of amino acids under CPL irradiation, a vacuum ultraviolet (VUV) CPL irradiation system was developed at the synchrotron light source UVSOR-III.

Variations of organic functional chemistry in carbonaceous matter from the asteroid 162173 Ryugu.

Primordial carbon delivered to the early earth by asteroids and meteorites provided a diverse source of extraterrestrial organics from pre-existing simple organic compounds, complex solar-irradiated macromolecules, and macromolecules from extended hydrothermal processing. Surface regolith collected by the Hayabusa2 spacecraft from the carbon-rich asteroid 162173 Ryugu present a unique opportunity to untangle the sources and processing history of carbonaceous matter. Here we show carbonaceous grains in Ryugu can be classified into three main populations defined by spectral shape: Highly aromatic (HA), Alkyl-Aromatic (AA), and IOM-like (IL).

Gamma-Ray-Induced Amino Acid Formation during Aqueous Alteration in Small Bodies: The Effects of Compositions of Starting Solutions.

Organic compounds, such as amino acids, are essential for the origin of life, and they may have been delivered to the prebiotic Earth from extra-terrestrial sources, such as carbonaceous chondrites. In the parent bodies of carbonaceous chondrites, the radioactive decays of short-lived radionuclides, such as Al, cause the melting of ice, and aqueous alteration occurs in the early stages of solar system formation. Many experimental studies have shown that complex organic matter, including amino acids and high-molecular-weight organic compounds, is produced by such hydrothermal processes.

Aqueous breakdown of aspartate and glutamate to n-ω-amino acids on the parent bodies of carbonaceous chondrites and asteroid Ryugu.

Amino acids in carbonaceous chondrites may have seeded the origin of life on Earth and possibly elsewhere. Recently, the return samples from a C-type asteroid Ryugu were found to contain amino acids with a similar distribution to Ivuna-type CI chondrites, suggesting the potential of amino acid abundances as molecular descriptors of parent body geochemistry. However, the chemical mechanisms responsible for the amino acid distributions remain to be elucidated particularly at low temperatures (<50°C).

Formation of Amino Acids and Carboxylic Acids in Weakly Reducing Planetary Atmospheres by Solar Energetic Particles from the Young Sun.

Life most likely started during the Hadean Eon; however, the environmental conditions which contributed to the complexity of its chemistry are poorly known. A better understanding of various environmental conditions, including global (heliospheric) and local (atmospheric, surface, and oceanic), along with the internal dynamic conditions of the early Earth, are required to understand the onset of abiogenesis. Herein, we examine the contributions of galactic cosmic rays (GCRs) and solar energetic particles (SEPs) associated with superflares from the young Sun to the formation of amino acids and carboxylic acids in weakly reduced gas mixtures representing the early Earth's atmosphere.

Macromolecular organic matter in samples of the asteroid (162173) Ryugu.

Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water).

Gamma-Ray-Induced Amino Acid Formation in Aqueous Small Bodies in the Early Solar System.

Carbonaceous chondrites contain life's essential building blocks, including amino acids, and their delivery of organic compounds would have played a key role in life's emergence on Earth. Aqueous alteration of carbonaceous chondrites is a widespread process induced by the heat produced by radioactive decay of nuclides like Al. Simple ubiquitous molecules like formaldehyde and ammonia could produce various organic compounds, including amino acids and complex organic macromolecules.

Comparison of stepwise and single-step pyrolysis GC/MS for natural complex macromolecular organic matter.

Pyrolysis gas chromatography-mass spectrometry is a useful technique for the analysis of complex organic matter. However, the pyrolysis temperatures must be carefully chosen to maximize the information obtained and, in parallel, minimize byproducts. One solution to accomplish this is the stepwise pyrolysis method, which has been employed to analyze complex mixtures of natural samples.

Space Exposure of Amino Acids and Their Precursors during the Tanpopo Mission.

Amino acids have been detected in extraterrestrial bodies such as carbonaceous chondrites (CCs), which suggests that extraterrestrial organics could be the source of the first life on Earth, and interplanetary dust particles (IDPs) or micrometeorites (MMs) are promising carriers of extraterrestrial organic carbon. Some amino acids found in CCs are amino acid precursors, but these have not been well characterized. The Tanpopo mission was conducted in Earth orbit from 2015 to 2019, and the stability of glycine (Gly), hydantoin (Hyd), isovaline (Ival), 5-ethyl-5-methylhydantoin (EMHyd), and complex organics formed by proton irradiation from CO, NH, and HO (CAW) in space were analyzed by high-performance liquid chromatography and/or gas chromatography/mass spectrometry.

Synthesis of Organic Matter in Aqueous Environments Simulating Small Bodies in the Solar System and the Effects of Minerals on Amino Acid Formation.

The extraterrestrial delivery of organics to primitive Earth has been supported by many laboratory and space experiments. Minerals played an important role in the evolution of meteoritic organic matter. In this study, we simulated aqueous alteration in small bodies by using a solution mixture of HCO and NH in the presence of water at 150 °C under different heating durations, which produced amino acids after acid hydrolysis.

An Another Protocol to Make Sulfur Embedded Ultrathin Sections of Extraterrestrial Small Samples.

Another protocol to make sulfur embedded ultrathin sections was developed for STXM-XANES, AFM-IR and TEM analyses of organic materials in small extraterrestrial samples. Polymerized liquid sulfur-instead of low-viscosity liquid sulfur-is the embedding media in this protocol. Due to high viscosity of the polymerized sulfur, the embedded samples stay near the surface of polymerized liquid sulfur, which facilitates trimming of glassy sulfur and ultramicrotomy of tiny embedded samples.

Alteration and Stability of Complex Macromolecular Amino Acid Precursors in Hydrothermal Environments.

The early Solar System comprised a broad area of abiotically created organic compounds, including interstellar organics which were integrated into planetesimals and parent bodies of meteorites, and eventually delivered to the early Earth. In this study, we simulated interstellar complex organic compounds synthesized by proton irradiation of a gas mixture of CO, NH, and HO, which are known to release amino acids after acid hydrolysis on the basis of Kobayashi et al. (1999) who reported that at the first stage of chemical evolution, the main compounds formed abiotically are complex organic compounds with high molecular weights.

A novel organic-rich meteoritic clast from the outer solar system.

The Zag meteorite which is a thermally-metamorphosed H ordinary chondrite contains a primitive xenolithic clast that was accreted to the parent asteroid after metamorphism. The cm-sized clast contains abundant large organic grains or aggregates up to 20 μm in phyllosilicate-rich matrix. Here we report organic and isotope analyses of a large (~10 μm) OM aggregate in the Zag clast.

Nucleic acid bases in Titan tholins and possible genetic systems in the Titan liquidosphere.

Titan is the largest moon of Saturn and possesses a dense atmosphere composed of nitrogen and methane. Various types of organic compounds (hydrocarbons, nitriles, etc.) have been found on Titan, which were generated by reactions taking place in its atmosphere.

Nanoscale infrared imaging analysis of carbonaceous chondrites to understand organic-mineral interactions during aqueous alteration.

Organic matter in carbonaceous chondrites is distributed in fine-grained matrix. To understand pre- and postaccretion history of organic matter and its association with surrounding minerals, microscopic techniques are mandatory. Infrared (IR) spectroscopy is a useful technique, but the spatial resolution of IR is limited to a few micrometers, due to the diffraction limit.

Geochemistry and the Origin of Life: From Extraterrestrial Processes, Chemical Evolution on Earth, Fossilized Life's Records, to Natures of the Extant Life.

In 2001, the first author (S.N.) led the publication of a book entitled "Geochemistry and the origin of life" in collaboration with Dr.

Organic matter in extraterrestrial water-bearing salt crystals.

Direct evidence of complex prebiotic chemistry from a water-rich world in the outer solar system is provided by the 4.5-billion-year-old halite crystals hosted in the Zag and Monahans (1998) meteorites. This study offers the first comprehensive organic analysis of the soluble and insoluble organic compounds found in the millimeter-sized halite crystals containing brine inclusions and sheds light on the nature and activity of aqueous fluids on a primitive parent body.

The search for and analysis of direct samples of early Solar System aqueous fluids.

We describe the current state of the search for direct, surviving samples of early, inner Solar System fluids-fluid inclusions in meteorites. Meteoritic aqueous fluid inclusions are not rare, but they are very tiny and their characterization is at the state of the art for most analytical techniques. Meteoritic fluid inclusions offer us a unique opportunity to study early Solar System brines in the laboratory.

One-pot synthesis of amino acid precursors with insoluble organic matter in planetesimals with aqueous activity.

The exogenous delivery of organic molecules could have played an important role in the emergence of life on the early Earth. Carbonaceous chondrites are known to contain indigenous amino acids as well as various organic compounds and complex macromolecular materials, such as the so-called insoluble organic matter (IOM), but the origins of the organic matter are still subject to debate. We report that the water-soluble amino acid precursors are synthesized from formaldehyde, glycolaldehyde, and ammonia with the presence of liquid water, simultaneously with macromolecular organic solids similar to the chondritic IOM.

Origin and evolution of prebiotic organic matter as inferred from the Tagish Lake meteorite.

The complex suite of organic materials in carbonaceous chondrite meteorites probably originally formed in the interstellar medium and/or the solar protoplanetary disk, but was subsequently modified in the meteorites' asteroidal parent bodies. The mechanisms of formation and modification are still very poorly understood. We carried out a systematic study of variations in the mineralogy, petrology, and soluble and insoluble organic matter in distinct fragments of the Tagish Lake meteorite.