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Context. More than 15 years after its landing on the surface of Titan, the data returned by the Huygens probe remain the only available in situ information on Titan's lower atmosphere and its methane content. Aims. In this work, we present a reanalysis of the Huygens probe data obtained by the Gas Chromatograph Mass Spectrometer (GCMS) instrument on board Huygens. GCMS measured the atmospheric composition almost continuously during the Huygens probe descent by acquiring mass spectra between 145 km of altitude and Titan's surface. We first focus on the recollection, reconstruction, and recalibration of the GCMS dataset to facilitate similar future work. Methods. We then reevaluate the methane vertical profile in Titan's lower atmosphere by applying novel mass spectra data-treatment methods to this dataset. Results. In addition to finding a slightly lower methane mixing ratio than those previously reported using GCMS measurements above the Huygens probe landing site, our work has revealed several kilometric to subkilometric-scale oscillations in the methane vertical profile below 30 km of altitude. Conclusions. We discuss several hypotheses that could explain these features, such as multiple layers of optically thin clouds or local convection cells, and strongly encourage the reanalysis of other Huygens datasets to further investigate these variations in the methane mixing ratio. [ABSTRACT FROM AUTHOR]

The Sample Analysis at Mars (SAM) instrument aboard the Curiosity Rover at Gale crater can characterize organic molecules from scooped and drilled samples via pyrolysis of solid materials. In addition, SAM can conduct wet chemistry experiments which enhance the detection of organic molecules bound in macromolecules and convert polar organic compounds into volatile derivatives amenable to gas chromatography‐mass spectrometry analyses. Specifically, N‐tert‐butyldimethylsilyl‐N‐methyltrifluoroacetamide (MTBSTFA) is a silylation reagent whereas tetramethylammonium hydroxide (TMAH) is a thermochemolysis methylation reagent. Shortly after arriving at Mars, the SAM team discovered that at least one of the MTBSFTA cups was leaking, contributing to a continuous background inside SAM with the potential to interfere with future TMAH reactions. Therefore, here we characterized possible interactions between the two reagents to determine byproducts and implications for the detection of indigenous organics. SAM‐like pyrolysis experiments supplemented with flash pyrolysis were accordingly conducted with fragments of the Murchison meteorite as a reference for exogenous organic matter delivered to Mars. Flash TMAH experiments yielded various aromatic acids, dicarboxylic acids, and amino acids while SAM‐like pyrolysis presented mixtures of methylated and non‐methylated compounds due to decreased reaction efficiency at slower ramp rates. All experiments in the presence of simulated MTBSTFA vapor produced pervasive silylated byproducts which co‐elute and obscure the identification of Murchison‐derived compounds. Despite challenges, a significant diversity of pyrolyzates and TMAH derivatives could still be identified in flash pyrolysis in presence of MTBSTFA. However SAM‐like experiments with TMAH and MTBSTFA are hindered by both decreased methylation yields and additional co‐eluting compounds. Plain Language Summary: The Sample Analysis at Mars (SAM) instrument aboard the Curiosity Rover on Mars can detect and analyze organic molecules that might be used by life as we know it. SAM does this by heating scooped soil or drill samples in order to vaporize and uncover any organic content that might be present. In addition, SAM can detect different types of organics that have more direct similarities to those used by modern organisms by adding one of two different kinds of chemical reagents prior to heating. However, shortly after arriving at Mars, it was discovered that one type of reagent, called MTBSTFA, was leaking inside of SAM with the potential to eventually interfere with the other, called TMAH, whenever it might be utilized. This study therefore reports on the chemical interactions between the two reagents and how they might impact the detection of indigenous organics on Mars. We determined heating samples in the presence of both reagents produces a series of byproducts which obscure the identification of organic compounds of interest. Still, despite analytical challenges, it is possible SAM may detect different types of organics which have yet to be detected on Mars with TMAH despite interference from leaking MTBSTA. Key Points: TMAH experiments with Murchison meteorite produces various aromatic acids, dicarboxylic acids, and amino acidsSAM‐like TMAH pyrolysis presents mixtures of methylated and non‐methylated compounds due to decreased reaction yields at slower ramp ratesAll experiments with simulated MTBSTFA vapor produce byproducts that obscure the identification of Murchison‐derived compounds [ABSTRACT FROM AUTHOR]

The Sample Analysis at Mars (SAM) suite instrument on board NASA's Curiosity rover has characterized the inorganic and organic chemical composition of seven samples from the Glen Torridon (GT) clay‐bearing unit. A variety of organic molecules were detected with SAM using pyrolysis (up to ∼850°C) and wet chemistry experiments coupled with evolved gas analysis (EGA) and gas chromatography‐mass spectrometry. SAM EGA and GCMS analyses revealed a greater diversity and abundance of sulfur‐bearing aliphatic and aromatic organic compounds in the sediments of this Gale crater unit than earlier in the mission. We also report the detection of nitrogen‐containing, oxygen‐containing, and chlorine‐containing molecules, as well as polycyclic aromatic hydrocarbons found in GT, although the sources of some of these organics may be related to the presence of chemical reagents in the SAM instrument background. However, sulfur‐bearing organics released at high temperature (≥600°C) are likely derived from Martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources and consistent with the presence of recalcitrant organic materials in the sample. The SAM measurements of the GT clay‐bearing unit expand the inventory of organic matter present in Gale crater and is also consistent with the hypothesis that clay minerals played an important role in the preservation of ancient refractory organic matter on Mars. These findings deepen our understanding of the past habitability and biological potential of Gale crater. Plain Language Summary: Organic molecules are essential to all life as we know it. Clay minerals are known on Earth for their high organic preservation potential and can be key indicators of past habitable environments. On Mars, the Glen Torridon (GT) region in Gale crater was first identified from orbit as a priority target for the Mars Science Laboratory mission due to its abundant clay minerals. To evaluate the organic preservation potential of this region, seven rock samples were collected and characterized using the Sample Analysis at Mars (SAM) instrument onboard the Curiosity rover. The SAM investigation indicated the presence of various organic compounds, including the first observation on Mars of some sulfur‐containing and ring‐structured organics and the highest abundance of sulfur organics observed to date. Our investigation of the sources of these organics revealed that while some of the sulfur‐bearing organics are likely Martian, a portion may also be related to the presence of chemical reagents carried in SAM, making attribution to a definitive source challenging. Nevertheless, these new SAM results confirm that ancient organic matter is preserved in the clay mineral bearing sediments of GT. Its origin—either meteoritic, abiotic or biotic—has yet to be established. Key Points: Curiosity explored the Glen Torridon region of Gale crater, which has a smectite‐rich mineralogy with high organic preservation potentialThe greatest diversity and abundance of sulfur‐bearing organics to date were detected in the solid samples by the SAM instrumentS‐bearing organics extracted ≥600°C and some aromatic compounds likely come from martian refractory organic matter [ABSTRACT FROM AUTHOR]

Most of the organics detected on Mars so far are aliphatic and aromatic organo‐chlorine compounds. The smallest were first identified by the thermal treatment of the solid samples by Viking in 1976; although at the time, they were attributed to contamination. Since 2012, a larger variety of structures have been identified by the Sample Analysis at Mars experiment aboard the Curiosity rover. Evidence suggests that the chlorohydrocarbons formed during pyrolysis of sedimentary materials. Laboratory experiments show that heating of samples containing oxychlorines, such as chlorates (ClO3−) and perchlorates (ClO4−), along with organic matter present at Mars' surface is the logical source of these compounds. Nevertheless, this discovery of indigenous organic matter in the Mars regolith raises important questions: How do the oxychlorines influence the pyrolysis of organics? What are the organics precursors of the organo‐chlorinated molecules detected on Mars? Is there a way to identify the parent molecules in a sample after pyrolysis? This paper presents the results of systematic laboratory experiments of the products formed during the pyrolysis of organic compounds from three chemical families—polycyclic aromatic hydrocarbons, amino acids, and carboxylic acids—in presence of calcium perchlorates. Results show that the polycyclic aromatic hydrocarbon parent molecules and most of the carboxylic acids are still detectable after pyrolysis in presence of calcium perchlorate and that the degradation and/or evolution of all parent molecules mostly depends on their chemical nature. In addition, we demonstrate that the chlorohydrocarbons detected on Mars by the Sample Analysis at Mars instrument could come from the three chemical families studied. Plain Language Summary: Organic molecules are the building blocks of life as we know it, and detecting them on the surface of Mars has been one of the major goals of Mars exploration. Viking landers in 1976, followed by the Curiosity rover in 2012, discovered simple chlorine‐bearing organics on Mars. These chlorohydrocarbons are known to be mainly produced by the instrument itself, through chemical reactions at high temperatures between other organic molecules thermally extracted from solid rock and soil samples that react with the oxidizing minerals present on Mars (e.g., perchlorates). Studying the influence of the minerals like perchlorates on the thermal extraction of different parent molecules requires thorough experimental studies like this one. Our work constrains the potential parent molecules of the chlorohydrocarbons detected on Mars in the presence of calcium perchlorate, thereby shedding light on the past and present habitability of Mars. Key Points: A systematic study reveals the influence of calcium perchlorate during the pyrolysis of organic compounds from various chemical familiesSome parent organics can be identified after thermal extraction as well as through the production of characteristic pyrolysis product(s)The precursors of the chlorohydrocarbons detected on Mars with the SAM instrument could originate from the three chemical families studied [ABSTRACT FROM AUTHOR]

The Sample Analysis at Mars (SAM) experiment on the National Aeronautics and Space Administration Curiosity rover seeks evidence of organic compounds on the surface of Mars. Since the beginning of the mission, various organic molecules have been detected and identified. While several have been demonstrated to be indigenous to the Martian soil and rocks analyzed, others appear to have been produced from sources internal to the experiment. The objective of this study is to build an exhaustive molecular database to support the interpretation of SAM results by identifying all the chemical species produced from Tenax® adsorbents, by determining (1) the thermal degradation by‐products of Tenax®, (2) the effect of Tenax® conditioning on the formation of Tenax® by‐products, (3) the impact of MTBSTFA or a mixture of MTBSTFA and DMF on Tenax® decomposition, and (4) the reaction between Tenax® and calcium perchlorate. Our results indicate that the by‐products of the SAM trap are due to the impact of trap heating, the impact of the derivatization reagent (MTBSTFA) and the presence of perchlorate in Martian soil. Some of these by‐products are observed in the SAM gas chromatograph mass spectrometer data from Mars. Plain Language Summary: The Sample Analysis at Mars (SAM) experiment onboard the Curiosity Rover has a polymer‐based chemical trap (Tenax®) that concentrates the evolved species from the Martian samples. We studied the impact that this trap could have on the SAM results when heated, when exposed to the chemical compounds used for sample processing (derivatization) and when exposed to Martian perchlorates. We conclude by demonstrating that some of the organic compounds detected in the background signal of the SAM chromatograms likely came from the degradation of Tenax®. This study will help to discriminate the endogenous organic compounds detected on Mars by SAM from the contamination. Key Points: In this article, we evaluate the impact of the Tenax® traps on the Sample Analysis at Mars experiment results, with concurrent implications for the future Martian Organic Molecule Analyser experiment resultsTenax® is an adsorbent resin used on SAM as a trap; it is an organic polymer that can be degraded into smaller moleculesBy‐products of Tenax® may contribute to the background of the SAM chromatogram. Here we identify them and the conditions of their production [ABSTRACT FROM AUTHOR]

Abstract: In 2005, the complex permittivity of the surface of Saturn's moon Titan was measured by the PWA‐MIP/HASI (Permittivity Wave Altimetry‐Mutual Impedance Probe/Huygens Atmospheric Structure Instrument) experiment on board the Huygens probe. The analysis of these measurements was recently refined but could not be interpreted in terms of composition due to the lack of knowledge on the low‐frequency/low‐temperature electrical properties of Titan's organic material, a likely key ingredient of the surface composition. In order to fill that gap, we developed a dedicated measurement bench and investigated the complex permittivity of analogs of Titan's organic aerosols called “tholins.” These laboratory measurements, together with those performed in the microwave domain, are then used to derive constraints on the composition of Titan's first meter below the surface based on both the PWA‐MIP/HASI and the Cassini Radar observations. Assuming a ternary mixture of water ice, tholin‐like dust and pores (filled or not with liquid methane), we find that at least 10% of water ice and 15% of porosity are required to explain observations. On the other hand, there should be at most 50–60% of organic dust. PWA‐MIP/HASI measurements also suggest the presence of a thin conductive superficial layer at the Huygens landing site. Using accurate numerical simulations, we put constraints on the electrical conductivity of this layer as a function of its thickness (e.g., in the range 7–40 nS/m for a 7‐mm thick layer). Potential candidates for the composition of this layer are discussed. [ABSTRACT FROM AUTHOR]

We report here on the coupling of a gas reactor with a VUV beamline at the SOLEIL synchrotron radiation facility. The reactor may be irradiated window-less with gas pressure up to the atmosphere. The photochemistry is monitored by a mass spectrometer gas analyzer. This set up, termed APSIS for Atmospheric Photochemistry Simulated by Synchrotron, has been used to simulate the atmosphere of Titan and to study the formation of the photochemical smog and the formation of tholins. [ABSTRACT FROM AUTHOR]

Tholins are polymeric hydrogenated carbon nitrides formed from N2:CH4 mixtures exposed to electrical discharges. They are complex disordered solids, and their structural chemistry and formation processes are not yet fully understood. Tholins have been widely adopted as useful analogs of reddish organic solids associated with planetary bodies or in interstellar space (e.g., Titan's aerosols, reddish surfaces of outer objects, interstellar organics, etc.) for fitting astronomical observations. However, there has been little evidence to date that they in fact constitute pertinent model materials, i. e. with chemical structure/composition similar to those presumed to be present in planetary or interstellar organic solids. In this contribution, we first review recent advances made regarding the determination of composition and structure of tholins produced in the laboratory. They point to a high chemical selectivity in the range of functional groups present, the control of unsaturation by nitrogen, and the highly disordered character of the structures. In a second section, we discuss the relationship between chemistry and the optical properties of tholins, and we point out the lack of a unique relationship between the shape and strength of the visible absorption bands and the chemical composition or structure of the model tholins. The tholins exhibit similarities with HCN “polymers”, that are suspected to be present in cometary refractory dust. This points to the existence of possible similar polymerisation processes, and it suggests they could also be used as analogs of N-rich cometary organics. Laboratory-based studies of cometary dust might offer new insights on the “chemical relevancy” of tholins, as combined micro-analytical techniques will allow direct comparison of chemical information between the materials produced. In a third section we present recent results pertaining to the search for such compounds in cometary grains (Stardust grains, interplanetary dust particles - IDPs). We show that some N-rich spots in stratospheric IDPs are rich in cyanide species, but no tholin-like compounds or polymeric HCN have been detected to date. [ABSTRACT FROM PUBLISHER]

Aerosols in Titan's atmosphere play an important role in determining its thermal structure. They also serve as sinks for organic vapours and can act as condensation nuclei for the formation of clouds, where the condensation efficiency will depend on the chemical composition of the aerosols. So far, however, no direct information has been available on the chemical composition of these particles. Here we report an in situ chemical analysis of Titan's aerosols by pyrolysis at 600 °C. Ammonia (NH3) and hydrogen cyanide (HCN) have been identified as the main pyrolysis products. This clearly shows that the aerosol particles include a solid organic refractory core. NH3 and HCN are gaseous chemical fingerprints of the complex organics that constitute this core, and their presence demonstrates that carbon and nitrogen are in the aerosols. [ABSTRACT FROM AUTHOR]

In the framework of the cometary sampling and composition (COSAC) experiment of the European Space Agency (ESA) Rosetta space mission to a comet, a new generation of porous polymer porous-layer open tubular (PLOT) columns has been investigated with the aim of separating the light organic compounds targeted by the experiment within the constraints of the operating conditions used in space. Both styrene-divinylbenzene and ethylene glycol-dimethyl acrylate-divinylbenzene porous polymers can be used to separate most of the target compounds, but the latter was selected because of its better separating properties. The most appropriate column characteristics were found to be 10 m length, 0.18 mm internal diameter, and 1–2 μm layer thickness, despite the low sample-loading capacity of such a column, which impairs its chromatographic performance. The influence of column overloading on retention properties and efficiency was, therefore, studied. To achieve the separation with optimum sensitivity, and within the in-situ time allowed for the analysis, it was also demonstrated that the maximum allowed temperature and reduced outlet pressure are required. Finally, it was shown that in the presence of water, the most abundant volatile compound in comets the separating properties of the studied columns are conserved. This paper thus demonstrates the suitability of the porous polymer PLOT column selected for the COSAC experiment and requirements for use in space; it is the first porous polymer PLOT column to be used in space exploration. [ABSTRACT FROM AUTHOR]

Due to its abundance and unique properties, water is a major actor in the formation and evolution of many planetary surfaces as well as a sensitive and reliable tracer of past geologic and climatic processes. Water ice is found in variable abundance at the surfaces of many Solar System objects, from the floor of permanently shadowed craters at the poles of Mercury to large fractions of the surfaces of several trans-Neptunian objects. With few exceptions, water is not found in pure form but associated to contaminants of various nature and concentration. These associations and the nature of the mixing and segregation processes that affect and control them are key for our understanding of some of the most important aspects of planetary evolution processes. The observation and characterization of water ice at the surface of Solar System objects is therefore among the primary scientific objectives of many space missions. The quantitative interpretation of remote sensing data in terms of surface composition and physical properties requires the use of complex physical models that rely on experimental data in two different ways. First, the models require as inputs the fundamental properties of the pure materials, such as the optical or dielectric constant. Second, the models can only be fully tested if their results are confronted to actual measurements performed on samples whose complexity comes close to the one encountered on natural planetary surfaces but which are nevertheless well-enough characterized to serve as reference. Such measurements are challenging as macroscopic ice-rich samples prepared as analogues of icy planetary surfaces tend to be unstable, the ice component being prone to metamorphism and phase change. The questions of the reproducibility of the samples and the relevance of the measurements are therefore critical. The Ice Laboratory at the University of Bern has been set up in 2010 to overcome some of these difficulties. We have developed protocols to prepare, store, handle and characterize various associations of ice with mineral and organics contaminants as analogues of different types of icy Solar System surfaces. The aims of this article are to present the context and background for our investigations, describe these protocols and associated hardware in a comprehensive way, provide quantitative characterization of the samples obtained using these protocols and summarize the main results obtained so far by experimenting with these samples. The current state and possible future evolutions of this project are then discussed in the context of the next generation of space missions to visit icy objects in the Solar System and longer term perspectives on future observations of protoplanetary discs and exoplanetary systems. [ABSTRACT FROM AUTHOR]

We describe three space experiments designed to expose to space conditions, and more specifically to solar UV radiation, selected samples of organic and mineral material. [ABSTRACT FROM PUBLISHER]

Biemann et al. calls into question our preliminary interpretations of our experimental results. A comparison of laboratory and flight measurements should settle the uncertainties he raises. In addition to evaluating instrumental characteristics such as the 'piston effect', a technique we used for injecting oven-gas content for gas chromatography–mass spectrometry (GC–MS), such studies should enable a wide range of possible compositions for Titan's aerosols to be investigated. Our aerosol collection and pyrolysis (ACP) measurements in Titan's atmosphere can then be revisited. [ABSTRACT FROM AUTHOR]

Biemann calls into question our preliminary interpretations of our experimental results. A comparison of laboratory and flight measurements should settle the uncertainties he raises. In addition to evaluating instrumental characteristics such as the 'piston effect', a technique we used for injecting oven-gas content for gas chromatography–mass spectrometry (GC–MS), such studies should enable a wide range of possible compositions for Titan's aerosols to be investigated. Our aerosol collection and pyrolysis (ACP) measurements in Titan's atmosphere can then be revisited. [ABSTRACT FROM AUTHOR]