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Laser-induced fluorescence spectroscopy is a useful laboratory and in situ technique for planetary exploration, with applications in biosignature detection and the search for life on Mars. However,...

Meteor physics can provide new clues about the size, structure, and density of cometary disintegration products, establishing a bridge between different research fields. From meteor magnitude data we have estimated the mass distribution of meteoroids from different cometary streams by using the relation between the luminosity and the mass obtained by Verniani. These mass distributions are in the range observed for dust particles released from comets 1P/Halley and 81P/Wild 2 as measured from spacecraft. From the derived mass distributions, we have integrated the incoming mass for the most significant meteor showers. By comparing the mass of the collected interplanetary dust particles (IDPs) with that derived for cometary meteoroids a gap of several orders of magnitude is encountered. The largest examples of fluffy particles are clusters of IDPs no larger than 100 μm in size (or 5 × 10–7 g in mass) while the largest cometary meteoroids are centimeter-sized objects. Such gaps can be explained by the fragmentation in the atmosphere of the original cometary particles. As an application of the mass distribution computations we describe the significance of the disruption of fragile comets in close approaches to Earth as a more efficient (and probably more frequent) way to deliver volatiles than direct impacts. We finally apply our model to quantify the flux of meteoroids from different meteoroid streams, and to describe the main physical processes contributing to the progressive decay of cometary meteoroids in the interplanetary medium., JMTR acknowledges financial support by the research project(PGC2018 097374-B-I00, funded by FEDER/Ministerio de Ciencia e Innovación – Agencia Estatal de Investigación. JB acknowledges the continuing support by the Deutsche Forschungsgemeinschaft and the Deutsches Zentrum für Luft- und Raumfahrt.

The martian meteorite ALH 84001 formed before ∼4.0 Ga, so it could have preserved information about habitability on early Mars and habitability since then. ALH 84001 is particularly important as it contains carbonate (and other) minerals that were deposited by liquid water, raising the chance that they may have formed in a habitable environment. Despite vigorous efforts from the scientific community, there is no accepted evidence that ALH 84001 contains traces or markers of ancient martian life-all the purported signs have been shown to be incorrect or ambiguous. However, the meteorite provides evidence for three distinct episodes of potentially habitable environments on early Mars. First is evidence that the meteorite's precursors interacted with clay-rich material, formed approximately at 4.2 Ga. Second is that igneous olivine crystals in ALH 84001 were partially dissolved and removed, presumably by liquid water. Third is, of course, the deposition of the carbonate globules, which occurred at ∼15-25°C and involved near-neutral to alkaline waters. The environments of olivine dissolution and carbonate deposition are not known precisely; hydrothermal and soil environments are current possibilities. By analogies with similar alteration minerals and sequences in the nakhlite martian meteorites and volcanic rocks from Spitzbergen (Norway), a hydrothermal environment is favored. As with the nakhlite alterations, those in ALH 84001 likely formed in a hydrothermal system related to a meteoroid impact event. Following deposition of the carbonates (at 3.95 Ga), ALH 84001 preserves no evidence of habitable environments, that is, interaction with water. The meteorite contains several materials (formed by impact shock at ∼3.9 Ga) that should have reacted readily with water to form hydrous silicates, but there is no evidence any formed.

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.

When an object enters the atmosphere it may be detected as a meteor. A bright meteor, called a fireball, may be a sign of a meteorite fall. Instrumentally observed meteorite falls provide unique opportunities to recover and analyse unweathered planetary samples supplemented with the knowledge on the Solar system orbit they had. To recover a meteorite from a fireball event, it is essential that recovery teams can be directed to a well-defined search area. Until recently, simulations showing the realistic mapping of a strewn field were difficult, in particular due to the large number of unknowns not directly retrieved from the fireball observations. These unknowns include the number of fragments and their aerodynamic properties, for which the masses of the fragments need to be assumed in a traditional approach. Here, we describe a new Monte Carlo model, which has already successfully assisted in several meteorite recoveries. The model is the first of its kind as it provides an adequate representation of the processes occurring during the luminous trajectory coupled together with the dark flight. In particular, the model comprises a novel approach to fragmentation modelling that leads to a realistic fragment mass distribution on the ground. We present strewn field simulations for the well-documented Košice and Neuschwanstein meteorite falls, which demonstrate good matches to the observations. We foresee that our model can be used to revise the flux of extra-terrestrial matter onto the Earth, as it provides a possibility of estimating the terminal mass of meteorite fragments reaching the ground. © The Author(s) 2021. This work was supported, in part, by the Academy of Finland project no. 325806 (PlanetS). We acknowledge Hadrien Devillepoix and Morgan Hollis for their supportive and valuable comments that encouraged us to improve this paper by adding the section on the strewn field of the Neuschwanstein meteorite fall. We thank Eleanor Sansom for helping us to proof read this paper and for stimulating discussion. We thank Juraj Tóth for providing additional coordinates of the documented Kosˇice meteorite fragments in addition to those published in Tóth et al. (2015). We thank Dieter Heinlein and Jürgen Oberst for discussing the circumstances of the known Neuschwanstein meteorite finds and difficulties of the ground search. We thank Panu Lahtinen (Finnish Meteorological Institute) and Peter Völger (Swedish Institute of Space Physics) for their help with obtaining the actual atmospheric data for the studied fireball events and valuable discussions. We thank all members of the Finnish Fireball Network and acknowledge Ursa Astronomical Association for the support with the Network coordination. We acknowledge fruitful collaboration with the colleagues at the Ural Federal University in organizing the field trips and prompt meteorite recoveries based on provided strewn field maps. The research at the Ural Federal University was supported by the Russian Foundation for Basic Research, project nos. 18-08-00074 and 19-05-00028.

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 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.

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.

Despite the generally hostile nature of the environments involved, chemistry does occur in space. Molecules are seen in environments that span a wide range of physical and chemical conditions and that clearly were created by a multitude of chemical processes, many of which differ substantially from those associated with traditional equilibrium chemistry. The wide range of environmental conditions and processes involved with chemistry in space yields complex populations of materials, and because the elements H, C, O, and N are among the most abundant in the universe, many of these are organic in nature, including some of direct astrobiological interest. Much of this chemistry occurs in "dense" interstellar clouds and protostellar disks surrounding forming stars because these environments have higher relative densities and more benign radiation fields than in stellar ejectae or the diffuse interstellar medium. Because these are the environments in which new planetary systems form, some of the chemical species made in these environments are expected to be delivered to the surfaces of planets where they can potentially play key roles in the origin of life. Because these chemical processes are universal and should occur in these environments wherever they are found, this implies that some of the starting materials for life are likely to be widely distributed throughout the universe.

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.

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

An interdisciplinary review of the chemical literature that points to a unifying scenario for the origin of life, referred to as the Primordial Multifunctional organic Entity (PriME) scenario, is provided herein. In the PriME scenario it is suggested that the Insoluble Organic Matter (IOM) in carbonaceous chondrites, as well as interplanetary dust particles from meteorites and comets may have played an important role in the three most critical processes involved in the origin of life, namely 1) metabolism, via a) the provision and accumulation of molecules that are the building blocks of life, b) catalysis (e.g., by templation), and c) protection of developing life molecules against radiation by excited state deactivation; 2) compartmentalization, via adsorption of compounds on the exposed organic surfaces in fractured meteorites, and 3) replication, via deaggregation, desorption and related physical phenomena. This scenario is based on the hitherto overlooked structural and physicochemical similarities between the IOM and the dark, insoluble, multifunctional melanin polymers found in bacteria and fungi and associated with the ability of these microorganisms to survive extreme conditions, including ionizing radiation. The underlying conceptual link between these two materials is strengthened by the fact that primary precursors of bacterial and fungal melanins (collectively referred to herein as allomelanins) are hydroxylated aromatic compounds like homogentisic acid and 1,8-dihydroxynaphthalene, and that similar hydroxylated aromatic compounds, including hydroxynaphthalenes, figure prominently among possible components of the organic materials on dust grains and ices in the interstellar matter, and may be involved in the formation of IOM in meteorites. Inspired by this rationale, a vis-& agrave;-vis review of the properties of IOM from various chondrites and non-nitrogenous allomelanin pigments from bacteria and fungi is provided herein. The unrecognized similarities between these materials may pave the way for a novel scenario at the origin of life, in which IOM-related complex organic polymers delivered to the early Earth are proposed to serve as PriME and were preserved and transformed in those primitive forms of life that shared the ability to synthesize melanin polymers playing an important role in the critical processes underlying the establishment of terrestrial eukaryotes.

Climate strikes, marsquakes and gaming AIs are among the year’s top stories. Climate strikes, marsquakes and gaming AIs are among the year’s top stories.

Exploration of microbial-meteorite redox interactions highlights the possibility of bioprocessing of extraterrestrial metal resources and reveals specific microbial fingerprints left on extraterrestrial material. In the present study, we provide our observations on a microbial-meteorite nanoscale interface of the metal respiring thermoacidophile Metallosphaera sedula. M. sedula colonizes the stony meteorite Northwest Africa 1172 (NWA 1172; an H5 ordinary chondrite) and releases free soluble metals, with Ni ions as the most solubilized. We show the redox route of Ni ions, originating from the metallic Ni° of the meteorite grains and leading to released soluble Ni2+. Nanoscale resolution ultrastructural studies of meteorite grown M. sedula coupled to electron energy loss spectroscopy (EELS) points to the redox processing of Fe-bearing meteorite material. Our investigations validate the ability of M. sedula to perform the biotransformation of meteorite minerals, unravel microbial fingerprints left on meteorite material, and provide the next step towards an understanding of meteorite biogeochemistry. Our findings will serve in defining mineralogical and morphological criteria for the identification of metal-containing microfossils.

International audience; 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.

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.

Besides delivering plausible prebiotic feedstock molecules and high-energy initiators, extraterrestrial impacts could also affect the process of abiogenesis by altering the early Earth's geological environment in which primitive life was conceived. We show that iron-rich smectites formed by reprocessing of basalts due to the residual post-impact heat could catalyze the synthesis and accumulation of important prebiotic building blocks such as nucleobases, amino acids and urea.

Context.The JAXA asteroid sample return mission Hayabusa2 acquired a huge quantity of data from the asteroid (162173) Ryugu during its 1.5 years in asteroid proximity orbit. On December 5, 2020 (Japan time), Hayabusa brought back to Earth a 5.4 g sample from Ryugu’s surface.Aims.We analyzed the near-infrared spectra of Ryugu, in particular the band at 2.72 μm, with the aim to investigate the hydrogen content of the H2O and OH−groups in hydrated phyllosilicates on Ryugu’s surface.Aims.We applied two different methods, normalized optical path length (NOPL) and effective single-particle absorption thickness (ESPAT), to the 3 μm region absorption band, and we compared the obtained spectral parameters with those obtained from carbonaceous chondrite meteorites whose H content was determined in the laboratory.Methods.We derived an exponential correlation between the selected meteorite H content and its respective ESPAT and NOPL parameters. The average value of the H content obtained on Ryugu’s surface with its relative variations, combining the results obtained with the two methods, is 0.52−0.21+0.16wt.%. These methods can be applied to other asteroids that exhibit a 3 μm region absorption band to estimate the mean average of H content.Results.The results of the ESPAT and NOPL methods used on the Ryugu spectral data present small variations across Ryugu’s surface and do not show any evident relation with the surface geomorphological structures. Our estimation of the global average H content of Ryugu is in agreement with those of several aqueously altered carbonaceous chondrites measured in the laboratory and is most similar to the H content of heated CM. The study of phyllosilicate H2O and OH−group hydrogen content on Ryugu and the derived method may be applied to other observed primitive asteroids. The obtained results will allow Solar System evolution models to be constrained and will allow the formation and evolution of the Solar System to be better understood.

In Earth's deep continental subsurface, where groundwaters are often isolated for >106 to 109 years, energy released by radionuclides within rock produces oxidants and reductants that drive metabolisms of non-photosynthetic microorganisms. Similar processes could support past and present life in the martian subsurface. Sulfate-reducing microorganisms are common in Earth's deep subsurface, often using hydrogen derived directly from radiolysis of pore water and sulfate derived from oxidation of rock-matrix-hosted sulfides by radiolytically derived oxidants. Radiolysis thus produces redox energy to support a deep biosphere in groundwaters isolated from surface substrate input for millions to billions of years on Earth. Here, we demonstrate that radiolysis by itself could produce sufficient redox energy to sustain a habitable environment in the subsurface of present-day Mars, one in which Earth-like microorganisms could survive wherever groundwater exists. We show that the source localities for many martian meteorites are capable of producing sufficient redox nutrients to sustain up to millions of sulfate-reducing microbial cells per kilogram rock via radiolysis alone, comparable to cell densities observed in many regions of Earth's deep subsurface. Additionally, we calculate variability in supportable sulfate-reducing cell densities between the martian meteorite source regions. Our results demonstrate that martian subsurface groundwaters, where present, would largely be habitable for sulfate-reducing bacteria from a redox energy perspective via radiolysis alone. We present evidence for crustal regions that could support especially high cell densities, including zones with high sulfide concentrations, which could be targeted by future subsurface exploration missions.

International audience; 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.

Many factors affect the health and physiology of human skin, with some of them arising from outer space. This contribution explores four celestial influences on the skin: (1) the sun's ultraviolet light, which has both beneficial and deleterious dermatologic effects, (2) meteorite injuries, (3) possible lunar effects on the body's health, and (4) cosmic radiation as a risk factor for skin cancer and pregnancy-related complications. Some of these extraterrestrial influences on skin health have taken on added significance as human beings increasingly spend more time at higher altitudes in aircraft, spaceships, and space stations.

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.

New measurements of Earth's building blocks point to a simpler water source

Asteroid (101955) Bennu, a near‐Earth object with a primitive carbonaceous chondrite‐like composition, was observed by the Origins, Spectral Interpretation, Resource Identification, and Security‐Regolith Explorer (OSIRIS‐REx) spacecraft to undergo multiple particle ejection events near perihelion between December 2018 and February 2019. The three largest events observed during this period, which all occurred 3.5 to 6 hr after local noon, placed numerous particles, Key Points Meteoroids derived from comets strike Bennu near perihelion once every 2 weeks on average with an impact kinetic energy >7,000 JThey can explain the particle sizes (

Tiny meteoroids entering the Earth's atmosphere and inducing meteor showers have long been thought to originate partly from cometary dust. Together with other dust particles, they form a huge cloud around the Sun, the zodiacal cloud. From our previous studies of the zodiacal light, as well as other independent methods (dynamical studies, infrared observations, data related to Earth's environment), it is now established that a significant fraction of dust particles entering the Earth's atmosphere comes from Jupiter-family comets (JFCs). This paper relies on our understanding of key properties of the zodiacal cloud and of comet 67P/Churyumov-Gerasimenko, extensively studied by the Rosetta mission to a JFC. The interpretation, through numerical and experimental simulations of zodiacal light local polarimetric phase curves, has recently allowed us to establish that interplanetary dust is rich in absorbing organics and consists of fluffy particles. The ground-truth provided by Rosetta presently establishes that the cometary dust particles are rich in organic compounds and consist of quite fluffy and irregular aggregates. Our aims are as follows: (1) to make links, back in time, between peculiar micrometeorites, tiny meteoroids, interplanetary dust particles, cometary dust particles, and the early evolution of the Solar System, and (2) to show how detailed studies of such meteoroids and of cometary dust particles can improve the interpretation of observations of dust in protoplanetary and debris disks. Future modeling of dust in such disks should favor irregular porous particles instead of more conventional compact spherical particles., 15 pages, 5 figures, accepted for publication in Planetary and Space Science

The world's meteorite collections contain a very rich picture of what the early Solar System would have been made of, however the lack of spatial context with respect to their parent population for these samples is an issue. The asteroid population is equally as rich in surface mineralogies, and mapping these two populations (meteorites and asteroids) together is a major challenge for planetary science. Directly probing asteroids achieves this at a high cost. Observing meteorite falls and calculating their pre-atmospheric orbit on the other hand, is a cheaper way to approach the problem. The Global Fireball Observatory (GFO) collaboration was established in 2017 and brings together multiple institutions (from Australia, USA, Canada, Morocco, Saudi Arabia, the UK, and Argentina) to maximise the area for fireball observation time and therefore meteorite recoveries. The members have a choice to operate independently, but they can also choose to work in a fully collaborative manner with other GFO partners. This efficient approach leverages the experience gained from the Desert Fireball Network (DFN) pathfinder project in Australia. The state-of-the art technology (DFN camera systems and data reduction) and experience of the support teams is shared between all partners, freeing up time for science investigations and meteorite searching. With all networks combined together, the GFO collaboration already covers 0.6% of the Earth's surface for meteorite recovery as of mid-2019, and aims to reach 2% in the early 2020s. We estimate that after 5 years of operation, the GFO will have observed a fireball from virtually every meteorite type. This combined effort will bring new, fresh, extra-terrestrial material to the labs, yielding new insights about the formation of the Solar System., Accepted in PSS. 19 pages, 9 figures

The desire to know how our Solar System came to be is a fundamental driving force for humanity's exploration of space. "Building new worlds-understanding Solar System beginnings" is a major cross-cutting theme in the 2010 Planetary Science Decadal Survey. Drastically improving our understanding of Solar System formation also has synergy effects. It provides unique information on one past protostellar system that helps astrophysicists understand stellar formation and protoplanetary disks. It provides context that increases the scientific return of missions exploring the current properties of the Solar System. Exploration of small primitive bodies is the key to reveal the origin of the Solar System. We conclude that substantial progress in understanding the formation of our Solar System during the 2023-2032 decade requires: 1) sample return missions to a Jupiter Family comet (ideally cryogenic) and/or Trojan asteroid to access primitive and previously unexplored types of material; 2) probing the interior of undisrupted primitive bodies with orbiters and placing decades of remote-sensing spectral information into a concrete mineralogical context with landers; 3) multi-body flyby missions to poorly explored target groups to better understand the diversity of body shapes and composition.

Carbon-based compounds are widespread throughout the Universe, including abiotic molecules that are the components of the life as we know it. This article reviews the space missions that have aimed to detect organic matter and biosignatures in planetary bodies of our solar system. While to date there was only one life-detection space mission, i.e., the Viking mission to Mars, several past and present space missions have searched for organic matter, paving the way for the future detection of signatures of extra-terrestrial life. This review also reports on the in-situ analysis of organic matter and sample-return missions from primitive bodies, i.e. comets and asteroids, providing crucial information on the conditions of the early solar system as well as on the building blocks of life delivered to the primitive Earth.

Aims. The existence of asteroid complexes produced by the disruption of these comets suggests that evolved comets could also produce high-strength materials able to survive as meteorites. We chose as an example comet 2P/Encke, one of the largest object of the so-called Taurid complex. We compare the reflectance spectrum of this comet with the laboratory spectra of some Antarctic ungrouped carbonaceous chondrites to investigate whether some of these meteorites could be associated with evolved comets. Methods. We compared the spectral behaviour of 2P/Encke with laboratory spectra of carbonaceous chondrites. Different specimens of the common carbonaceous chondrite groups do not match the overall features and slope of the comet 2P/Encke. By testing anomalous carbonaceous chondrites, we found two meteorites: Meteorite Hills 01017 and Grosvenor Mountains 95551, which could be good proxies for the dark materials that formed this short-period comet. We hypothesise that these two meteorites could be rare surviving samples, either from the Taurid complex or another compositionally similar body. In any case, it is difficult to get rid of the effects of terrestrial weathering in these Antarctic finds, and further studies are needed. A future sample return from the so-called dormant comets could also be useful to establish a ground truth on the materials forming evolved short-period comets. Results. As a natural outcome, we think that identifying good proxies of 2P/Encke-forming materials might have interesting implications for future sample-return missions to evolved, potentially dormant, or extinct comets. Understanding the compositional nature of evolved comets is particularly relevant in the context of the future mitigation of impact hazard from these dark and dangerous projectiles., J.M.T.R. and S.T. acknowledge financial support from the Spanish Ministry (PGC2018-097374-B-I00, PI: JMTR). J.L.L. is grateful to ICREA Academia program and funding from Generalitat de Catalunya (2017 SGR 128). US Antarctic meteorite samples are recovered by the Antarctic Search for Meteorites (ANSMET) program which has been funded by NSF and NASA, and characterized and curated by the Department of Mineral Sciences of the Smithsonian Institution and Astromaterials Acquisition and Curation Office at NASA Johnson Space Center.

The meteoroid risk in circumterrestrial space is basically caused by 1-10 mm meteoroid bodies. Meteoroid particles of such dimensions cannot be registered by modern monitoring astronomical instruments. Observable are only meteor phenomena they cause. This work analyses the activity of main meteor showers over several years and assesses the danger from meteoroids with a size of more than 1 mm. The results of calculating the meteoroid risk during these showers’ maximum activity periods have shown that despite its low values it is sufficiently close to the maximum allowable risk. This already constitutes a recognizable danger, and such a danger needs to be taken into consideration.

The biogenic elements, H, C, N, O, P and S, have a long cosmic history, whose evolution can still be observed in diverse locales of the known universe, from interstellar clouds of gas and dust, to pre-stellar cores, nebulas, protoplanetary discs, planets and planetesimals. The best analytical window into this cosmochemical evolution as it neared Earth has been provided so far by the small bodies of the Solar System, some of which were not significantly altered by the high gravitational pressures and temperatures that accompanied the formation of larger planets and may carry a pristine record of early nebular chemistry. Asteroids have delivered such records, as their fragments reach the Earth frequently and become available for laboratory analyses. The Carbonaceous Chondrite meteorites (CC) are a group of such fragments with the further distinction of containing abundant organic materials with structures as diverse as kerogen-like macromolecules and simpler compounds with identical counterparts in Earth's biosphere. All have revealed a lineage to cosmochemical synthetic regimes. Several CC show that asteroids underwent aqueous alteration of their minerals or rock metamorphism but may yet yield clues to the reactivity of organic compounds during parent-body processes, on asteroids as well as larger ocean worlds and planets. Whether the exogenous delivery by meteorites held an advantage in Earth's molecular evolution remains an open question as many others regarding the origins of life are. Nonetheless, the natural samples of meteorites allow exploring the physical and chemical processes that might have led to a selected chemical pool amenable to the onset of life. Graphical Abstract ᅟ.