Constraints for Use of Ultraviolet Spectropolarimetry to Detect Chiral Amino Acids from Comets

Life is pervasive on planet Earth, but whether life is ubiquitous in the Galaxy and sustainable over timescales comparable to stellar evolution is unknown. Evidence suggests that life first appeared on Earth more than 3.77 Gyr ago, during a period of heavy meteoric bombardment. Amino acids, the building blocks of proteins, have been demonstrated to exist in interstellar ice. As such, the contribution of space-generated amino acids to those existing on Earth should be considered. However, detection of space amino acids is challenging. In this study, we used analytical data from several meteorites and in situ measurements of the comet 67P/Churyumov-Gerasimenko collected by the Rosetta probe to evaluate the detectability of alanine by ultraviolet spectropolarimetry. Alanine is the second-most abundant amino acid after glycine and is optically active. This chirality produces a unique signature that enables reliable identification of this amino acid using the imprint of optical rotatory dispersion (ORD) and circular dichroism (CD) in the ultraviolet spectrum (130-230 nm). Here, we show that the ORD signature could be detected in comets by using ultraviolet spectropolarimetric observations conducted at middle size space observatories. These observations can also provide crucial information for the study of sources of enantiomeric imbalance on Earth.

Martian Magmatic Clay Minerals Forming Vesicles: Perfect Niches for Emerging Life?

Mars was habitable in its early history, but the consensus is that it is quite inhospitable today, in particular because its modern climate cannot support stable liquid water at the surface. Here, we report the presence of magmatic Fe/Mg clay minerals within the mesostasis of the martian meteorite NWA 5790, an unaltered 1.3 Ga nakhlite archetypal of the martian crust. These magmatic clay minerals exhibit a vesicular texture that forms a network of microcavities or pockets, which could serve as microreactors and allow molecular crowding, a necessary step for the emergence of life. Because their formation does not depend on climate, such niches for emerging life may have been generated on Mars at many periods throughout its history, regardless of the stability or availability of liquid water at the surface.

Petrology and mineralogy of the Viñales meteorite, the latest fall in Cuba

The new Cuban chondrite, Viñales, fell on February first, 2019 at Pinar del Rio, northwest of Cuba (22°37'10″N, 83°44'34″W). A total of about 50-100 kg of the meteorite were collected and the masses of individual samples are in a range 2-1100 g. Two polished thin sections were studied by optical microscope, Raman spectroscopy and electron microprobe analysis in this study. The meteorite mainly consists of olivine (Fa24.6), low-Ca pyroxene (Fs20.5), and troilite and Fe-Ni metal, with minor amounts of feldspar (Ab82.4-84.7). Three poorly metamorphosed porphyritic olivine-pyroxene and barred olivine chondrules are observed. The homogeneous chemical compositions and petrographic textures indicate that Viñales is a L6 chondrite. The Viñales has fresh black fusion crust with layered structure, indicating it experienced a high temperature of ∼1650°C during atmospheric entry. Black shock melt veins with width of 100-600 μm are pervasive in the Viñales and olivine, bronzite, and metal phases are dominate minerals of the shock melt vein. The shock features of major silicate minerals suggest a shock stage S3, partly S4, and the shock pressure could be >10 GPa.

Experimental Investigation of the Formation of Formaldehyde by Hadean and Noachian Impacts

Formaldehyde (FA) is an important precursor in the abiotic synthesis of major biomolecules including amino acids, sugars, and nucleobases. Thus, spontaneous formation of prebiotic FA must have been crucial for the chemical origin of life. The frequent impacts of meteorites and asteroids on Hadean Earth have been considered one of the abiotic synthetic processes of organic compounds. However, the impact-induced formation of FA from CO₂ as the major atmospheric constituent has not been confirmed yet. This study investigated the formation of FA in impact-induced reactions among meteoritic minerals, bicarbonate, gaseous nitrogen, and water to simulate the abiotic process experimentally. Products were analyzed with ultra-high-performance liquid chromatography/tandem mass spectrometry and powder X-ray diffraction techniques. The results show the formation of FA and oxidation of metallic iron to siderite in the impact shock experiments. This indicates that this important prebiotic molecule was also synthesized by impacts of iron-bearing meteorites/asteroids on the Hadean oceans. The impact events might have generated spatially and temporally FA-enriched localized environments. Moreover, the impact-induced synthesis of FA may have also occurred on Noachian Mars given the presence of liquid water and a CO₂-N₂-rich atmosphere on the planet.

Viroids and the Origin of Life

Viroids are non-coding circular RNA molecules with rod-like or branched structures. They are often ribozymes, characterized by catalytic RNA. They can perform many basic functions of life and may have played a role in evolution since the beginning of life on Earth. They can cleave, join, replicate, and undergo Darwinian evolution. Furthermore, ribozymes are the essential elements for protein synthesis of cellular organisms as parts of ribosomes. Thus, they must have preceded DNA and proteins during evolution. Here, we discuss the current evidence for viroids or viroid-like RNAs as a likely origin of life on Earth. As such, they may also be considered as models for life on other planets or moons in the solar system as well as on exoplanets.

'The moon quivered like a snake': A medieval chronicler, lunar explosions, and a puzzle for modern interpretation

Despite some scepticism, the suggestion by Hartung in 1976 that the report in the chronicle of Gervase of Canterbury corresponded to a meteorite impact with the moon in 1178, creating the Giordano Bruno crater, retains considerable support, particularly in popular scientific writing. Nevertheless, a series of studies of images of the crater from orbiting satellites, although confirming its young geological age, have indicated that it was not created within recorded human history. In this paper, we examine astronomical entries in Gervase's chronicle relating to eclipses and conclude that, despite there being descriptions of miracles elsewhere in the manuscript, he himself was a reliable reporter of astronomical events. On this basis an alternative suggestion can be put forward for the splitting of the horns and writhing of the body of the new moon, reported to Gervase: atmospheric turbulence. Although general atmospheric turbulence has been previously dismissed as too small an effect, it is possible to show that the description is consistent with viewing the new moon through a column of hot air from a fire, at a moderate distance and out of the line of sight of the observers. This interpretation of the medieval evidence as credible but unrelated to a lunar event is consistent with twenty-first century lunar studies.

Shock Processing of Amino Acids Leading to Complex Structures-Implications to the Origin of Life

The building blocks of life, amino acids, are believed to have been synthesized in the extreme conditions that prevail in space, starting from simple molecules containing hydrogen, carbon, oxygen and nitrogen. However, the fate and role of amino acids when they are subjected to similar processes largely remain unexplored. Here we report, for the first time, that shock processed amino acids tend to form complex agglomerate structures. Such structures are formed on timescales of about 2 ms due to impact induced shock heating and subsequent cooling. This discovery suggests that the building blocks of life could have self-assembled not just on Earth but on other planetary bodies as a result of impact events. Our study also provides further experimental evidence for the ‘threads’ observed in meteorites being due to assemblages of (bio)molecules arising from impact-induced shocks.

Growth on Carbohydrates from Carbonaceous Meteorites Alters the Immunogenicity of Environment-Derived Bacterial Pathogens

The last decade has witnessed a renewed interest in space exploration. Public and private institutions are investing considerable effort toward the direct exploration of the Moon and Mars, as well as more distant bodies in the solar system. Both automated and human-crewed spacecraft are being considered in these efforts. As inevitable fellow travelers on the bodies of astronauts, spaceships, or equipment, terrestrial microorganisms will undoubtedly come into contact with extraterrestrial environments, despite stringent decontamination. These microorganisms could eventually adapt and grow in their new habitats, where they might potentially recolonize and lead to the infection of the human space travelers. In this article, we demonstrate that clinically relevant bacterial species found in the environment are able to grow in minimal media with sugar compounds identified in extraterrestrial carbon sources. As a surrogate model, we used carbohydrates previously isolated from carbonaceous meteorites. The bacteria underwent an adaptation process that caused structural modifications in the cell envelope that sparked changes in pathogenic potential, both in vitro and in vivo. Understanding the adaptation of microorganisms exposed to extraterrestrial environments, with subsequent changes in their immunogenicity and virulence, requires a comprehensive analysis of such scenarios to ensure the safety of major space expeditions in the decades to come.

Cometary Glycolaldehyde as a Source of pre-RNA Molecules

Over 200 molecules have been detected in multiple extraterrestrial environments, including glycolaldehyde (C₂(H₂O)₂, GLA), a two-carbon sugar precursor that has been detected in regions of the interstellar medium. Its recent in situ detection on the nucleus of comet 67P/Churyumov-Gerasimenko and through remote observations in the comae of others provides tantalizing evidence that it is common on most (if not all) comets. Impact experiments conducted at the Experimental Impact Laboratory at NASA's Johnson Space Center have shown that samples of GLA and GLA mixed with montmorillonite clays can survive impact delivery in the pressure range of 4.5 to 25 GPa. Extrapolated to amounts of GLA observed on individual comets and assuming a monotonic impact rate in the first billion years of Solar System history, these experimental results show that up to 10²³ kg of cometary GLA could have survived impact delivery, with substantial amounts of threose, erythrose, glycolic acid, and ethylene glycol also produced or delivered. Importantly, independent of the profile of the impact flux in the early Solar System, comet delivery of GLA would have provided (and may continue to provide) a reservoir of starting material for the formose reaction (to form ribose) and the Strecker reaction (to form amino acids). Thus, comets may have been important delivery vehicles for starting molecules necessary for life as we know it.

Cometary Delivery of Hydrogen Cyanide to the Early Earth

Delivery of water and organics by asteroid and comet impacts may have influenced prebiotic chemistry on the early Earth. Some recent prebiotic chemistry experiments emphasize hydrogen cyanide (HCN) as a feedstock molecule for the formation of sugars, ribonucleotides, amino acids, and lipid precursors. Here, we assess how much HCN originally contained in a comet would survive impact, using parametric temperature and pressure profiles together with a time-dependent chemistry model. We find that HCN survival mainly depends on whether the impact is hot enough to thermally decompose H₂O into reactive radicals, and HCN is therefore rather insensitive to the details of the chemistry. In the most favorable impacts (low impact angle, low velocity, small radius), this temperature threshold is not reached, and intact delivery of HCN is possible. We estimate the global delivery of HCN during a period of Early and Late Heavy Bombardment of the early Earth, as well as local HCN concentrations achieved by individual impacts. In the latter case, comet impacts can provide prebiotically interesting HCN levels for thousands to millions of years, depending on properties of the impactor and of the local environment.

The Role of Meteorite Impacts in the Origin of Life

The conditions, timing, and setting for the origin of life on Earth and whether life exists elsewhere in our solar system and beyond represent some of the most fundamental scientific questions of our time. Although the bombardment of planets and satellites by asteroids and comets has long been viewed as a destructive process that would have presented a barrier to the emergence of life and frustrated or extinguished life, we provide a comprehensive synthesis of data and observations on the beneficial role of impacts in a wide range of prebiotic and biological processes. In the context of previously proposed environments for the origin of life on Earth, we discuss how meteorite impacts can generate both subaerial and submarine hydrothermal vents, abundant hydrothermal-sedimentary settings, and impact analogues for volcanic pumice rafts and splash pools. Impact events can also deliver and/or generate many of the necessary chemical ingredients for life and catalytic substrates such as clays as well. The role that impact cratering plays in fracturing planetary crusts and its effects on deep subsurface habitats for life are also discussed. In summary, we propose that meteorite impact events are a fundamental geobiological process in planetary evolution that played an important role in the origin of life on Earth. We conclude with the recommendation that impact craters should be considered prime sites in the search for evidence of past life on Mars. Furthermore, unlike other geological processes such as volcanism or plate tectonics, impact cratering is ubiquitous on planetary bodies throughout the Universe and is independent of size, composition, and distance from the host star. Impact events thus provide a mechanism with the potential to generate habitable planets, moons, and asteroids throughout the Solar System and beyond.

Explaining the Variations in Isotopic Ratios in Meteoritic Amino Acids

Measurements of the isotopic abundances in meteoritic amino acids have found enhancements of ²H/H, ¹⁵N/¹⁴N, and ¹³C/¹²C in the amino acids in the meteorites studied. We show that they are consistent with the processing of the constituents of the meteorites by electron antineutrinos that would be expected from a core-collapse supernova or neutron-star merger. Using theoretical electron antineutrino cross-sections, we are able to predict these isotopic ratio variations depending on the time-integrated antineutrino flux at the site where the amino acids were processed.

The Albedo of Ryugu: Evidence for a High Organic Abundance, as Inferred from the Hayabusa2 Touchdown Maneuver

The Hayabusa2 mission successfully collected samples from the asteroid Ryugu last year and will return these to Earth in December 2020. It is anticipated that the samples will enable the analysis of terrestrially uncontaminated organic matter and minerals. Such analyses are in turn expected to elucidate the evolution of organic matter through Solar System history, including the origination and processing of biogenically important molecules, which could have been utilized by the first organisms on Earth. In anticipation, studies have made predictions concerning the properties of Ryugu, including its composition. The spectral characteristics of Ryugu, such as albedo, have been employed to relate the asteroid to members of the carbonaceous chondrite group that have been identified on Earth. However, the recent Hayabusa2 touchdown highlights a disparity between the color of surfaces of displaced platy fragments, indicating a brightening trend for the surface exposed to space compared to that facing into the body. Here we present a mass balance calculation with reference to data from the literature, which indicates that Ryugu may contain a significantly higher abundance of organic matter (likely >50%) than the currently most accepted meteorite analogues. A high organic content may result in high levels of extractable organic matter for the second touchdown site, where the spacecraft sampled freshly exposed material. However, high abundances of insoluble aromatic/graphitic rich organic matter may be present in the first touchdown site, which sampled the surface of Ryugu that had been exposed to space. Moreover, we suggest that the potentially high organic abundance and the rubble-pile nature of Ryugu may originate from the capture of rocky debris by a comet nucleus and subsequent water-organic-mineral interactions and sublimation of water ice.

Thiophenes on Mars: Biotic or Abiotic Origin?

The question whether organic compounds occur on Mars remained unanswered for decades. However, the recent discovery of various classes of organic matter in martian sediments by the Curiosity rover seems to strongly suggest that indigenous organic compounds exist on Mars. One intriguing group of detected organic compounds were thiophenes, which typically occur on Earth in kerogen, coal, and crude oil as well as in stromatolites and microfossils. Here we provide a brief synopsis of conceivable pathways for the generation and degradation of thiophenes on Mars. We show that the origin of thiophene derivatives can either be biotic or abiotic, for example, through sulfur incorporation in organic matter during early diagenesis. The potential of thiophenes to represent martian biomarkers is discussed as well as a correlation between abundances of thiophenes and sulfate-bearing minerals. Finally, this study provides suggestions for future investigations on Mars and in Earth-based laboratories to answer the question whether the martian thiophenes are of biological origin.

Eukaryotic Colonization of Micrometer-Scale Cracks in Rocks: A "Microfluidics" Experiment Using Naturally Weathered Meteorites from the Nullarbor Plain, Australia

The advent of microfluidics has revolutionized the way we understand how microorganisms propagate through microporous spaces. Here, we apply this understanding to the study of how endolithic environmental microorganisms colonize the interiors of sterile rock. The substrates used for our study are stony meteorites from the Nullarbor Plain, Australia; a semiarid limestone karst that provides an ideal setting for preserving meteorites. Periodic flooding of the Nullarbor provides a mechanism by which microorganisms and exogenous nutrients may infiltrate meteorites. Our laboratory experiments show that environmental microorganisms reach depths greater than 400 μm by propagating through existing brecciation, passing through cracks no wider than the diameter of a resident cell (i.e., ∼5 μm). Our observations are consistent with the propagation of these eukaryotic cells via growth and cell division rather than motility. The morphology of the microorganisms changed as a result of propagation through micrometer-scale cracks, as has been observed previously for bacteria on microfluidic chips. It has been suggested that meteorites could have served as preferred habitats for microorganisms on ancient Mars. Based on our results, the depths reached by terrestrial microorganisms within meteorites would be sufficient to mitigate against the harmful effects of ionizing radiation, such as UV light, in Earth's deserts and potentially on Mars, if similar processes of microbial colonization had once been active there. Thus, meteorites landing in ancient lakes on Mars, that later dried out, could have been some of the last inhabited locations on the surface, serving as refugia before the planet's surface became inhospitable. Finally, our observations suggest that terrestrial microorganisms can colonize very fine cracks within meteorites (and potentially spaceships and rovers) on unexpectedly short timescales, with important implications for both recognition of extraterrestrial life in returned geological samples and planetary protection.

Critically testing olivine-hosted putative martian biosignatures in the Yamato 000593 meteorite-Geobiological implications

On rocky planets such as Earth and Mars the serpentinization of olivine in ultramafic crust produces hydrogen that can act as a potential energy source for life. Direct evidence of fluid-rock interaction on Mars comes from iddingsite alteration veins found in martian meteorites. In the Yamato 000593 meteorite, putative biosignatures have been reported from altered olivines in the form of microtextures and associated organic material that have been compared to tubular bioalteration textures found in terrestrial sub-seafloor volcanic rocks. Here, we use a suite of correlative, high-sensitivity, in situ chemical, and morphological analyses to characterize and re-evaluate these microalteration textures in Yamato 000593, a clinopyroxenite from the shallow subsurface of Mars. We show that the altered olivine crystals have angular and micro-brecciated margins and are also highly strained due to impact-induced fracturing. The shape of the olivine microalteration textures is in no way comparable to microtunnels of inferred biological origin found in terrestrial volcanic glasses and dunites, and rather we argue that the Yamato 000593 microtextures are abiotic in origin. Vein filling iddingsite extends into the olivine microalteration textures and contains amorphous organic carbon occurring as bands and sub-spherical concentrations <300 nm across. We propose that a martian impact event produced the micro-brecciated olivine crystal margins that reacted with subsurface hydrothermal fluids to form iddingsite containing organic carbon derived from abiotic sources. These new data have implications for how we might seek potential biosignatures in ultramafic rocks and impact craters on both Mars and Earth.

Enceladus: First Observed Primordial Soup Could Arbitrate Origin-of-Life Debate

A recent breakthrough publication has reported complex organic molecules in the plumes emanating from the subglacial water ocean of Saturn's moon Enceladus (Postberg et al., 2018, Nature 558:564-568). Based on detailed chemical scrutiny, the authors invoke primordial or endogenously synthesized carbon-rich monomers (<200 u) and polymers (up to 8000 u). This appears to represent the first reported extraterrestrial organics-rich water body, a conceivable milieu for early steps in life's origin ("prebiotic soup"). One may ask which origin-of-life scenario appears more consistent with the reported molecular configurations on Enceladus. The observed monomeric organics are carbon-rich unsaturated molecules, vastly different from present-day metabolites, amino acids, and nucleotide bases, but quite chemically akin to simple lipids. The organic polymers are proposed to resemble terrestrial insoluble kerogens and humic substances, as well as refractory organic macromolecules found in carbonaceous chondritic meteorites. The authors posit that such polymers, upon long-term hydrous interactions, might break down to micelle-forming amphiphiles. In support of this, published detailed analyses of the Murchison chondrite are dominated by an immense diversity of likely amphiphilic monomers. Our specific quantitative model for compositionally reproducing lipid micelles is amphiphile-based and benefits from a pronounced organic diversity. It thus contrasts with other origin models, which require the presence of very specific building blocks and are expected to be hindered by excess of irrelevant compounds. Thus, the Enceladus finds support the possibility of a pre-RNA Lipid World scenario for life's origin.

Phobos LIFE (Living Interplanetary Flight Experiment)

The Planetary Society's Phobos Living Interplanetary Flight Experiment (Phobos LIFE) flew in the sample return capsule of the Russian Federal Space Agency's Phobos Grunt mission and was to have been a test of one aspect of the hypothesis that life can move between nearby planets within ejected rocks. Although the Phobos Grunt mission failed, we present here the scientific and engineering design and motivation of the Phobos LIFE experiment to assist with the scientific and engineering design of similar future experiments. Phobos LIFE flew selected organisms in a simulated meteoroid. The 34-month voyage would have been the first such test to occur in the high-radiation environment outside the protection of Earth's magnetosphere for more than a few days. The patented Phobos LIFE "biomodule" is an 88 g cylinder consisting of a titanium outer shell, several types of redundant seals, and 31 individual Delrin sample containers. Phobos LIFE contained 10 different organisms, representing all three domains of life, and one soil sample. The organisms are all very well characterized, most with sequenced genomes. Most are extremophiles, and most have flown in low Earth orbit. Upon return from space, the health and characteristics of organisms were to have been compared with controls that remained on Earth and have not yet been opened.

Photolysis of Cometary Organic Dust Analogs on the EXPOSE-R2 Mission at the International Space Station

We describe the results obtained on a set of organic samples that have been part of the experiment "Photochemistry on the Space Station (PSS)" on the EXPOSE-R2 mission conducted on the EXPOSE-R facility situated outside the International Space Station (ISS). The organic samples were prepared in the Catania laboratory by 200 keV He⁺ irradiation of N₂:CH₄:CO icy mixtures deposited at 17 K, on vacuum UV (VUV) transparent MgF₂ windows. This organic material contains different chemical groups, including triple CN bonds, that are thought to be of interest for astrobiology. It is widely accepted that materials similar to that produced in the laboratory by ion irradiation of frozen ices could be present in some astrophysical environments such as comets. Once expelled from comets, these materials are exposed to solar radiation during their interplanetary journey. In the young Solar System, some of these processed materials could have reached early Earth and contributed to its chemical and prebiotic evolution. The samples were exposed for 16 months to the unshielded solar UV photons. It was found that, if an interplanetary dust particle (IDP) containing organic material (50% vol) is large enough (>20-30 μm), relevant chemical groups, such as those containing the CN triple bond, can survive for many years (>10⁴ years) in the interplanetary medium.

Multiwall and bamboo-like carbon nanotubes from the Allende chondrite: A probable source of asymmetry

This study presents multiwall and bamboo-like carbon nanotubes found in samples from the Allende carbonaceous chondrite using high-resolution transmission electron microscopy (HRTEM). A highly disordered lattice observed in this material suggests the presence of chiral domains in it. Our results also show amorphous and poorly-graphitized carbon, nanodiamonds, and onion-like fullerenes. The presence of multiwall and bamboo-like carbon nanotubes have important implications for hypotheses that explain how a probable source of asymmetry in carbonaceous chondrites might have contributed to the enantiomeric excess in soluble organics under extraterrestrial scenarios. This is the first study proving the existence of carbon nanotubes in carbonaceous chondrites.

Survival of Extremotolerant Bacteria from the Mukundpura Meteorite Impact Crater

Carbonaceous meteorites provide clues with regard to prebiotic chemistry and the origin of life. Geological Survey of India recorded a carbonaceous chondrite meteorite fall in Mukundpura, India, on June 6, 2017. We conducted a study to investigate the microbial community that survived the meteorite impact. 16S rRNA metagenomic sequencing indicates the presence of Actinobacteria, Proteobacteria, and Acidobacteria in meteorite impact soil. Comparative phylogenetic analysis revealed an intriguing abundance of class Bacilli in the impact soil. Bacillus thermocopriae IR-1, a moderately thermotolerant organism, was isolated from a rock, impacted by the Mukundpura meteorite. We investigated the resilience of B. thermocopriae IR-1 to environmental stresses and impact shock in a Reddy shock tube. Bacillus thermocopriae IR-1 survived (28.82% survival) the effect of shock waves at a peak shock pressure of 300 kPa, temperature 400 K, and Mach number of 1.47. This investigation presents the first report on the effect of impact shock on B. thermocopriae IR-1. The study is also the first report on studying the microbial diversity and isolation of bacteria from impact crater soil immediately after meteorite impact event.

Prebiotic Syntheses Under Shock in the Water - Formamide - Potassium Bicarbonate - Sodium Hydroxide System

Syntheses under shock in nitrogen bubbled samples of the water - formamide - bicarbonate - sodium hydroxide system at pH 8.63, 9.46 and 10.44 were performed in the stainless steel preservation capsules. The maximum temperature and pressure in the capsules reached 545 K and 12.5 GPa respectively. Using the LC-MS-MS analysis, the 21 synthesis products have been identified, including amines and polyamines, carboxamide, acetamide and urea derivatives, compounds containing aniline, pyrrolidine, pyrrole, imidazole, as well as alcohol groups. It was found that the Fischer-Tropsch-type syntheses with catalysis on the surface of the stainless steel of the conservation capsule associated with the adsorbed hydrogen cyanide reactions and transamidation processes play the main role in the shock syntheses. Formation reactions of all the above-mentioned compounds have been suggested. It was proposed that hydrogen cyanide, ammonia, isocyanic acid, aminonitrile, aminoacetonitrile, as well as adsorbed species H(a), CH(a), CH2(a), CHOH(a), NH2(a) and H2CNH(a) are especially important for the formation of the products. A reduction reaction of adsorbed bicarbonate with hydrogen to formaldehyde has been first postulated. In the studied system also classical reactions take place - Wöhler's synthesis of urea and Butlerov's synthesis of methenamine. It was suggest that material of meteorites may be an effective catalyst in the Fischer-Tropsch-type syntheses at falling of the iron-nickel meteorites in the water - formamide regions on the early Earth. It was concluded that life could have originated due to the impact of meteorites on alkaline water-formamide lakes located near volcanoes on the early Earth.

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. These reactions are considered to provide crucial evidence for chemical reactions which may have occurred in the atmosphere of primitive Earth. Cassini discovered several lakes of liquid methane and ethane on Titan's surface; in addition, the presence of ammonia water in its sub-surface was implied. In order to simulate the chemical reactions in Titan's atmosphere, gas mixtures of nitrogen and methane have been exposed to plasma discharges to synthesize complex organic matters. In this study, we focused on the formation of nucleic acid bases and related compounds recovered from synthesized Titan tholins. The five nucleic acid bases that terrestrial life uses (adenine, cytosine, thymine, guanine, and uracil) have already been reported to be present in synthesized Titan tholins. Purines and pyrimidines, including the five aforementioned nucleic acid bases, were extracted from synthesized Titan tholins and analyzed by HPLC and LC/MS. As a result, the pyrimidine bases of isocytosine and 2, 4-diaminopyrimidine were detected together with the terrestrial nucleic acid bases of adenine, uracil, and cytosine. The results obtained in conjunction with those from previous studies show that some nucleic acid bases and related pyrimidine bases are found in synthesized Titan tholins, suggesting that chemical evolutions toward xenogenetic systems could occur in Titan's environment.

Spatially-resolved mineral identification and depth profiling on chondrules from the primitive chondrite Elephant Moraine 14017 with confocal Raman spectroscopy

Confocal Raman spectroscopy is effective in unveiling structures of minerals without destruction from surface to certain depth. In this study, we introduce an application of confocal Raman spectroscopy on minerals in a primitive chondritic meteorite. The experimental lateral resolution on silicate minerals in this study is ~1.0 μm. Raman spectrum of mesostasis in a named "Tear Drop" chondrule, a spherule object from a primitive chondrite, of Elephant Moraine 14017 (EET 14017) shows a broad feature indicating amorphous phase, which is a common characteristic of primitive chondrule mesostasis. Weak intensities of 825 and 858 cm^-1 peaks were observed in the glassy mesostasis, probably originated from olivine below the surface. A plagioclase-rich chondrule (PRC-1) of EET 14017 was investigated with Raman spectroscopy, which contains two different occurrences of plagioclase: lath-shaped and interstitial grains. The strong intensity of 488 and 505 cm^-1 (plagioclase) and weak intensity of 461 cm^-1 band were observed on the lath-shaped plagioclase. The weak 461 cm^-1 peak from the plagioclase is probably from the subsurface quartz. Raman spectrum of interstital plagioclase in PRC-1 shows 488 and 505 cm^-1 bands and weak pyroxene bands. Depth profiling conducted on the interstitial plagioclase clearly shows that pyroxene exists below the surface. High-lateral resolution and well-resolved depth profiling with the confocal Raman spectroscopy allows us to identify tiny grains and investigate hidden phases underneath the surface without destruction of extraterrestrial materials.

THE BERT AND PEGGY DUPONT LECTURE: SCIENCE AND CULTURE FROM THE HUBBLE SPACE TELESCOPE

The Hubble Space Telescope has been in Earth orbit for almost 30 years, returning an amazing variety of scientific discoveries. It can be pointed via ground command to the entire panoply of astronomical objects, from nearby targets in our solar system to the most distant objects in the known universe. While these wonderful scientific results were expected by the project's founders, what have been more surprising are the cultural aspects of the program. Hubble has been embraced by the general public to an extent unprecedented for complex scientific facilities. Not only are its images widely known for their beauty, but the project itself has repeatedly entered the popular lexicon as an example of a technological pinnacle. We present examples of the numerous scientific successes, as well as popular culture memes related to Hubble. Finally, it is also important to ponder the broader question of why we conduct astronomical research.