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This paper presents our first experimental results on the photodegradation at 147 and 122 nm of hexamethylenetetramine (HMT). This molecule, suspected to be present on cometary grains, could be responsible for extended sources of CN and HCN in comets. We show that if HMT is quite resistant to direct photolysis under vacuum, interactions with water vapor photoproducts, which could happen in inner comae, lead to a much more efficient degradation with formation of HCN, NH3 and other N bearing molecules. Thus HMT could act as a parent or grand parent molecule for observed extended sources. However, additional source with greater degradation efficiency is certainly required to account observations in outer comae. [Copyright &y& Elsevier]

During ESA's Rosetta science mission, the COSIMA instrument collected dust particles in the coma of Comet 67P/Churyumov-Gerasimenko during two years near the comet's nucleus. The largest particles are about 1 m m in size. The collection process involved a low velocity impact on porous gold-black surfaces, often resulting in breakup, from which information on structural properties has previously been derived (Langevin et al., 2016). However, some of the particles were collected with little damage, but fragmented due to charging during subsequent secondary ion mass spectrometry. This report shows that the details of this electrical fragmentation support the concept of the existence of stable units with sizes of tens of μ m within the incoming cometary dust particles prior to collection, possibly representing remnants of the early accretion processes. [Display omitted] • We collected dust in the near coma of Comet 67P/Churyumov-Gerasimenko. • Dust particles become charged when exposed to the ion beam of the COSIMA secondary ion mass spectrometer and are fragmented by electrical forces. • The results confirm the existence of stable sub-units of several tens of μ m in size within the cometary matter. • Consequently, 67/P refractory cometary matter can be considered pristine on size scales of tens of μ m and smaller. • These sub-units are possible remnants of the early accretion processes. [ABSTRACT FROM AUTHOR]

For decades of space exploration, mass spectrometry has proven to be a reliable instrumentation for the characterisation of the nature and energy of ionic and neutral, atomic and molecular species in the interplanetary medium and upper planetary atmospheres. It has been used as well to analyse the chemical composition of planetary and small bodies environments. The chemical complexity of these environments calls for the need to develop a new generation of mass spectrometers with significantly increased mass resolving power. The recently developed Orbitrap TM mass analyser at ultra-high resolution shows promising adaptability to space instrumentation, offering improved performances for in situ measurements. In this article, we report on our project named “Cosmorbitrap” aiming at demonstrating the adaptability of the Orbitrap technology for in situ space exploration. We present the prototype that was developed in the laboratory for demonstration of both technical feasibility and analytical capabilities. A set of samples containing elements with masses ranging from 9 to 208 u has been used to evaluate the performance of the analyser, in terms of mass resolving power (reaching 474,000 at m / z 9) and ability to discriminate between isobaric interferences, accuracy of mass measurement (below 15 ppm) and determination of relative isotopic abundances (below 5%) of various samples. We observe a good agreement between the results obtained with the prototype and those of a commercial instrument. As the background pressure is a key parameter for in situ exploration of atmosphere planetary bodies, we study the effect of background gas on the performance s of the Cosmorbitrap prototype, showing an upper limit for N 2 in our set-up at 10 −8 mbar. The results demonstrate the strong potential to adapt this technology to space exploration. [ABSTRACT FROM AUTHOR]

On the orbiter of the Rosetta spacecraft, the Cometary Secondary Ion Mass Analyser (COSIMA) will provide new in situ insights about the chemical composition of cometary grains all along 67P/Churyumov–Gerasimenko (67P/CG) journey until the end of December 2015 nominally. The aim of this paper is to present the pre-calibration which has already been performed as well as the different methods which have been developed in order to facilitate the interpretation of the COSIMA mass spectra and more especially of their organic content. The first step was to establish a mass spectra library in positive and negative ion mode of targeted molecules and to determine the specific features of each compound and chemical family analyzed. As the exact nature of the refractory cometary organic matter is nowadays unknown, this library is obviously not exhaustive. Therefore this library has also been the starting point for the research of indicators, which enable to highlight the presence of compounds containing specific atom or structure. These indicators correspond to the intensity ratio of specific peaks in the mass spectrum. They have allowed us to identify sample containing nitrogen atom, aliphatic chains or those containing polyaromatic hydrocarbons. From these indicators, a preliminary calibration line, from which the N/C ratio could be derived, has also been established. The research of specific mass difference could also be helpful to identify peaks related to quasi-molecular ions in an unknown mass spectrum. The Bayesian Positive Source Separation (BPSS) technique will also be very helpful for data analysis. This work is the starting point for the analysis of the cometary refractory organic matter. Nevertheless, calibration work will continue in order to reach the best possible interpretation of the COSIMA observations. [ABSTRACT FROM AUTHOR]

Abstract: The photochemistry of an organic compound in extraterrestrial environments is related to its photoabsorption cross sections in the VUV/UV range (<300nm). Such data, especially in the VUV range (<200nm) are quite scarce in the literature. This paper presents an experimental setup and associated methodology to measure VUV/UV spectra of thin films of organic molecules. The case of adenine is extensively discussed as an example study. The absorption cross sections spectrum of adenine between 115 and 300nm is measured from transmission measurements and accurate calculation of the thickness of our samples set thanks to interferometry techniques and infrared spectrometry. From these data, the infrared integrated band strength of solid adenine between 3600 and 1970cm−1 has also been measured and is equal to 7.9×10–16±4%cmmolecule−1. The use of the VUV/UV spectrum to estimate the photolysis rate constant is discussed and compared to direct kinetic measurements available in the literature for low Earth orbit experiments. However the lack of measurements of the photodissociation quantum yield as a function of the wavelength prevents a precise calculation. VUV/UV cross section spectrum is yet a necessity to conduct either proper kinetic studies on optically thin samples (less than 2nm in the VUV for adenine) or an appropriate modeling for optically thick samples. [Copyright &y& Elsevier]

Abstract: The presence of polyoxymethylene (POM) in cometary grains has been debated years ago. Although never proven, its presence can not be excluded. Rosetta, the ESA mission to comet 67P/Churyumov–Gerasimenko, may answer this question. On board the spacecraft, COSIMA (COmetary Secondary Ion Mass Analyzer) will analyze the grains ejected from the nucleus using a Time Of Flight Secondary Ion Mass Spectrometer (TOF-SIMS). In this paper we report the extent to which COSIMA will be able to detect POM if this compound is present on cometary grains. We have analyzed two kinds of POM polymers with a laboratory model of COSIMA. Positive mass spectra display alternating sequence of peaks with a separation of 30.011Da between 1 and 600Da related to formaldehyde and its oligomers but also to the fragmentation of these oligomers. The separation of 30.011Da of numbers peaks, corresponding to the fragmentation into H2CO is characteristic of POM and we show that it could be highlight by mathematical treatment. POM lifetime on COSIMA targets have also been studied as POM is thermally instable. It can be concluded that the cometary grains analysis have to be planned not too long after their collection in order to maximize the chances to detect POM. This work was supported by the Centre National d''Etudes Spatiales (CNES). [Copyright &y& Elsevier]

Abstract: The detection and identification of carbonates on Mars are of prime importance to establish the evolution of its atmosphere, correlated to the history of the liquid water, or even to determine the existence of a possible ancient biological activity. Till date, no large deposits of carbonates have been found. In fact, their detection is specific to local areas and in very low amounts. The absence of such deposits is commonly attributed to the harsh environmental conditions at the surface of Mars. Additionally, the presence of UV radiation has been proposed to explain their photodecomposition and hence their absence. However, contradictory results from laboratory experiments mimicking Mars’ surface UV radiation did not resolve the behaviour of carbonates in such an environment, which is why we exposed, in low Earth orbit and in laboratory experiments, both abiotic and biotic calcium carbonates to UV radiation of wavelength above 200nm, the same spectral distribution as the one reaching the surface of Mars. For low Earth orbit (LEO) exposure, this was done for the UVolution experiment on board the BIOPAN ESA module, which was set outside a Russian Foton automated capsule, and exposed to space conditions for 12 days in September 2007. The targeted carbonates are biominerals and abiotic samples. Our laboratory results mainly show that the exposed carbonates appear to be stable to UV radiation if directly exposed to it. The LEO experiment results tend to the same conclusion, but the integrated exposition time to Solar UV during the experiment is not sufficient to be conclusive. However, the stability of the biominerals derived from the laboratory experiment could strengthen the interest to explore deeper their potential as life records at Mars. Hence, they should be considered as primary targets for in situ analyses during future missions. [Copyright &y& Elsevier]

Abstract: Solar UV radiation is a major source of energy for chemical evolution of organic materials in the Solar System. Therefore studies on the photostability of organic compounds in extraterrestrial environments are of prime importance for the understanding of the extraterrestrial origin of organic materials on Earth. A series of organic samples have been photolysed in Earth orbit during the ESA BIOPAN 6 mission (14–26/09/2007). Their photochemical lifetime has been measured and compared to results recorded in the laboratory using a lamp that simulates the solar radiation in the VUV domain. The half-lives at a distance of 1AU from the Sun have been measured for glycine, xanthine, hypoxanthine, adenine, guanine, urea, carbon suboxide polymer ((C3O2) n ) and HCN polymer. They range from a few days to a lower limit of a few tens of days for the most photoresistant (e.g. adenine, guanine, hypoxanthine). Lifetimes measured in terrestrial orbit are very different from those derived with laboratory experiments. These measurements confirm that it is difficult to simulate the solar spectrum below 200nm in the laboratory. Results are discussed and highlight the necessity to conduct experiments in orbit, and for longer duration. It also appears that the laboratory measurements made in VUV must be extrapolated very cautiously to the different environments they are supposed to simulate. [ABSTRACT FROM AUTHOR]

Between Aug. 2014 and Sept. 2016, while ESA's cornerstone mission Rosetta was operating in the vicinity of the nucleus and in the coma of comet 67P/Churyumov-Gerasimenko, the COSIMA instrument collected a large number of dust particles with diameters up to a millimeter. Positive or negative ions were detected by a time-of-flight secondary ion mass spectrometer (TOF-SIMS) and the composition of selected particles was deduced. Many of the negative ion mass spectra show, besides mass peaks at the correct position, an additional, extended contribution at the lower mass side caused by partial charging of the dust. This effect, usually avoided in SIMS applications, can in our case be used to obtain information on the electrical properties of the collected cometary dust particles, such as the specific resistivity (ρ r > 1. 2 ⋅ 10 10 Ω m) and the real part of the relative electrical permittivity (ε r < 1.2). From these values a lower limit for the porosity is derived (P > 0.8). Image 1 • Dust particles from the Coma of Comet 67P/Churyumov-Gerasimenko are of low electrical conductivity. • Their electrical permittivity is close to 1 (< 1.2) and their porosity is high (>80%). • During TOF-SIMS analysis they charge up to about 130 V within a second. • Asymmetrical shapes of negative ion mass lines can be a valuable source of information in TOF-SIMS. [ABSTRACT FROM AUTHOR]