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The Philae lander of the Rosetta space mission made a non-nominal landing on comet 67P/Churyumov-Gerasimenko on November 12, 2014. Shortly after, using the limited power available from Philae's batteries, the COSAC instrument performed a single 18-minutes gas chromatogram, which has remained unpublished until now due to the lack of identifiable elution. This work shows that, despite the unsuccessful drilling of the comet and deposition of surface material in the SD2 ovens, the measurements from the COSAC instrument were executed nominally. We describe an automated search for extremely small deviations from noise and discuss the possibility of a signal from ethylene glycol at m/z 31. Arguments for and against this detection are listed, but the results remain inconclusive. Still, the successful operations of an analytical chemistry laboratory on a cometary nucleus gives great hope for the future of space exploration., (© 2022 The Authors. ChemPlusChem published by Wiley-VCH GmbH.)

This work studies ultrasonic propagation in liquid and ice water drops. The effect of porosity on attenuation of ultrasonic waves in the drops is also explored. The motivation of this research was the possible application of ultrasonic techniques to the study of interstellar and cometary ice analogs. These ice analogs, made by vapor deposition onto a cold substrate at 10 K, can display high porosity values up to 40%. We found that the ultrasonic pulse was fully attenuated in such ice, and decided to grow ice samples by freezing a liquid drop. Several experiments were performed using liquid or frozen water drops with and without pores. An ultrasonic pulse was transmitted through each drop and measured. This method served to estimate the ultrasonic velocity of each drop by measuring drop size and time-of-flight of ultrasonic transmission. Propagation of ultrasonic waves in these drops was also simulated numerically using the SimNDT program developed by the authors. After that, the ultrasonic velocity was related with the porosity using a micromechanical model. It was found that a low value of porosity in the ice is sufficient to attenuate the ultrasonic propagation. This explains the observed lack of transmission in porous astrophysical ice analogs.

The Atacama Large Millimeter Array has allowed a detailed observation of molecules in protoplanetary disks, which can evolve toward solar systems like our own. While CO, [Formula: see text], HCO, and [Formula: see text] are often abundant species in the cold zones of the disk, [Formula: see text] or [Formula: see text] are only found in a few regions, and more-complex organic molecules are not observed. We simulate, experimentally, ice processing in disks under realistic conditions, that is, layered ices irradiated by soft X-rays. X-ray emission from young solar-type stars is thousands of times brighter than that of today's sun. The ice mantle is composed of a [Formula: see text]:[Formula: see text]:[Formula: see text] mixture, covered by a layer made of [Formula: see text] and CO. The photoproducts found desorbing from both ice layers to the gas phase during the irradiation converge with those detected in higher abundances in the gas phase of protoplanetary disks, providing important insights on the nonthermal processes that drive the chemistry in these objects., Competing Interests: The authors declare no competing interest.

Context: Sulphur is one of the most abundant elements in the Universe. Surprisingly, sulphuretted molecules are not as abundant as expected in the interstellar medium and the identity of the main sulphur reservoir is still an open question., Aims: Our goal is to investigate the H 2 S chemistry in dark clouds, as this stable molecule is a potential sulphur reservoir., Methods: Using millimeter observations of CS, SO, H 2 S, and their isotopologues, we determine the physical conditions and H 2 S abundances along the cores TMC 1-C, TMC 1-CP, and Barnard 1b. The gas-grain model Nautilus is used to model the sulphur chemistry and explore the impact of photo-desorption and chemical desorption on the H 2 S abundance., Results: Our modeling shows that chemical desorption is the main source of gas-phase H 2 S in dark cores. The measured H 2 S abundance can only be fitted if we assume that the chemical desorption rate decreases by more than a factor of 10 when n H > 2 × 10 4 . This change in the desorption rate is consistent with the formation of thick H 2 O and CO ice mantles on grain surfaces. The observed SO and H 2 S abundances are in good agreement with our predictions adopting an undepleted value of the sulphur abundance. However, the CS abundance is overestimated by a factor of 5 - 10. Along the three cores, atomic S is predicted to be the main sulphur reservoir., Conclusions: The gaseous H 2 S abundance is well reproduced, assuming undepleted sulphur abundance and chemical desorption as the main source of H 2 S. The behavior of the observed H 2 S abundance suggests a changing desorption efficiency, which would probe the snowline in these cold cores. Our model, however, highly overestimates the observed gas-phase CS abundance. Given the uncertainty in the sulphur chemistry, we can only conclude that our data are consistent with a cosmic elemental S abundance with an uncertainty of a factor of 10.

We present the first detection of gas phase S 2 H in the Horsehead, a moderately UV-irradiated nebula. This confirms the presence of doubly sulfuretted species in the interstellar medium and opens a new challenge for sulfur chemistry. The observed S 2 H abundance is ~5×10 -11 , only a factor 4-6 lower than that of the widespread H 2 S molecule. H 2 S and S 2 H are efficiently formed on the UV-irradiated icy grain mantles. We performed ice irradiation experiments to determine the H 2 S and S 2 H photodesorption yields. The obtained values are ~1.2×10 -3 and <1×10 -5 molecules per incident photon for H 2 S and S 2 H, respectively. Our upper limit to the S 2 H photodesorption yield suggests that photo-desorption is not a competitive mechanism to release the S 2 H molecules to the gas phase. Other desorption mechanisms such as chemical desorption, cosmic-ray desorption and grain shattering can increase the gaseous S 2 H abundance to some extent. Alternatively, S 2 H can be formed via gas phase reactions involving gaseous H 2 S and the abundant ions S + and SH + . The detection of S 2 H in this nebula could be therefore the result of the coexistence of an active grain surface chemistry and gaseous photo-chemistry.

The absorption of light to create Wannier-Mott excitons is a fundamental feature dictating the optical and photovoltaic properties of low band gap, high permittivity semiconductors. Such excitons, with an electron-hole separation an order of magnitude greater than lattice dimensions, are largely limited to these semiconductors but here we find evidence of Wannier-Mott exciton formation in solid carbon monoxide (CO) with a band gap of >8  eV and a low electrical permittivity. This is established through the observation that a change of a few degrees K in deposition temperature can shift the electronic absorption spectra of solid CO by several hundred wave numbers, coupled with the recent discovery that deposition of CO leads to the spontaneous formation of electric fields within the film. These so-called spontelectric fields, here approaching 4×10^{7}  V m^{-1}, are strongly temperature dependent. We find that a simple electrostatic model reproduces the observed temperature dependent spectral shifts based on the Stark effect on a hole and electron residing several nm apart, identifying the presence of Wannier-Mott excitons. The spontelectric effect in CO simultaneously explains the long-standing enigma of the sensitivity of vacuum ultraviolet spectra to the deposition temperature.

Comets harbor the most pristine material in our solar system in the form of ice, dust, silicates, and refractory organic material with some interstellar heritage. The evolved gas analyzer Cometary Sampling and Composition (COSAC) experiment aboard Rosetta's Philae lander was designed for in situ analysis of organic molecules on comet 67P/Churyumov-Gerasimenko. Twenty-five minutes after Philae's initial comet touchdown, the COSAC mass spectrometer took a spectrum in sniffing mode, which displayed a suite of 16 organic compounds, including many nitrogen-bearing species but no sulfur-bearing species, and four compounds—methyl isocyanate, acetone, propionaldehyde, and acetamide—that had not previously been reported in comets., (Copyright © 2015, American Association for the Advancement of Science.)

Carbon dioxide (CO2) is one of the most relevant and abundant species in astrophysical and atmospheric media. In particular, CO2 ice is present in several solar system bodies, as well as in interstellar and circumstellar ice mantles. The amount of CO2 in ice mantles and the presence of pure CO2 ice are significant indicators of the temperature history of dust in protostars. It is therefore important to know if CO2 is mixed with other molecules in the ice matrix or segregated and whether it is present in an amorphous or crystalline form. We apply a multidisciplinary approach involving IR spectroscopy in the laboratory, theoretical modeling of solid structures, and comparison with astronomical observations. We generate an unprecedented highly amorphous CO2 ice and study its crystallization both by thermal annealing and by slow accumulation of monolayers from the gas phase under an ultrahigh vacuum. Structural changes are followed by IR spectroscopy. We also devise theoretical models to reproduce different CO2 ice structures. We detect a preferential in-plane orientation of some vibrational modes of crystalline CO2. We identify the IR features of amorphous CO2 ice, and, in particular, we provide a theoretical explanation for a band at 2,328 cm(-1) that dominates the spectrum of the amorphous phase and disappears when the crystallization is complete. Our results allow us to rule out the presence of pure and amorphous CO2 ice in space based on the observations available so far, supporting our current view of the evolution of CO2 ice.

A compendium of different solid carbonaceous materials detected in space is presented, focussing on the search for organic matter of prebiotic interest. This journey takes us from the carbon grains likely formed in the atmospheres of evolved stars to organic grain mantles made from ice processing thought to be present in dense interstellar clouds and circumstellar regions, making a stop in solar system objects that could have delivered organic species to the early Earth. The most abundant carbon materials detected to date in space appear to be of little biological relevance. On the other hand, organic refractory residues, made in the laboratory from UV-photoprocessing followed by warm-up of interstellar ice analogs, are a hydrocarbon material rich in O and N containing chemical compounds that could act as initiators of prebiotic chemistry. A similar material might be present in dust grains inside dense clouds or circumstellar regions, some comets, and as a minor component in carbonaceous chondrites. We use infrared spectroscopy as a tool to spot organic refractory matter in various space environments. The delivery of organic materials via comets, (micro-) meteorites, and interplanetary dust particles to the primitive Earth might have contributed as a starting material for prebiotic chemistry. To test this hypothesis, it is first essential to characterize the composition of exogenous organic matter.

Biological cofactors include functionalized derivatives of cyclic tetrapyrrole structures that incorporate different metal ions. They build up structural partnerships with proteins, which play a crucial role in biochemical reactions. Porphyrin, chlorin, bacteriochlorin, and corrin are the basic structures of cofactors (heme, chlorophyll, bacteriochlorophyll, siroheme, F 430, and vitamin B12). Laboratory and theoretical work suggest that the molecular building blocks of proteins (alpha-amino acids) and nucleic acids (carbohydrates, purines, and pyrimidines) were generated under prebiotic conditions. On the other hand, experimental data on the prebiotic chemistry of cofactors are rare. We propose to search directly for the pathways of the formation of cofactors in the laboratory. Herein we report on the detection of N-heterocycles and amines in the room-temperature residue obtained after photo- and thermal processing of an interstellar ice analogue under high vacuum at 12 K. Among them, hexahydro-1,3,5-triazine and its derivatives, together with monopyrrolic molecules, are precursors of porphinoid cofactors. Hexahydropyrimidine was also detected. This is the first detection of these compounds in experiments simulating circumstellar/interstellar conditions. Except for 2-aminopyrrole and 2,4-diaminofuran, which were only found in 13C-labeled experiments, all the reported species were detected in both 12C- and 13C-labeled experiments, excluding contamination. The molecules reported here might be present in circumstellar/interstellar grains and cometary dust and could be detected by the Stardust and Rosetta missions.

Amino acids identified in the Murchison chondritic meteorite by molecular and isotopic analysis are thought to have been delivered to the early Earth by asteroids, comets, and interplanetary dust particles where they may have triggered the appearance of life by assisting in the synthesis of proteins via prebiotic polycondensation reactions [Oró, J. (1961) Nature 190, 389-390; Chyba, C. F. & Sagan, C. (1992) Nature 355, 125-132]. We report the identification of diamino acids in the Murchison meteorite by new enantioselective GC-MS analyses. dl-2,3-diaminopropanoic acid, dl-2,4-diaminobutanoic acid, 4,4'-diaminoisopentanoic acid, 3,3'-diaminoisobutanoic acid, and 2,3-diaminobutanoic acid were detected in the parts per billion range after chemical transformation into N,N-diethoxycarbonyl ethyl ester derivatives. The chiral diamino acids show a racemic ratio. Laboratory data indicate that diamino acids support the formation of polypeptide structures under primitive Earth conditions [Brack, A. & Orgel, L. E. (1975) Nature 256, 383-387] and suggest polycondensation reactions of diamino acids into early peptide nucleic acid material as one feasible pathway for the prebiotic evolution of DNA and RNA genomes [Joyce, G. F. (2002) Nature 418, 214-221]. The results obtained in this study favor the assumption that not only amino acids (as the required monomers of proteins) form in interstellar/circumstellar environments, but also the family of diamino monocarboxylic acids, which might have been relevant in prebiotic chemistry.

Amino acids are the essential molecular components of living organisms on Earth, but the proposed mechanisms for their spontaneous generation have been unable to account for their presence in Earth's early history. The delivery of extraterrestrial organic compounds has been proposed as an alternative to generation on Earth, and some amino acids have been found in several meteorites. Here we report the detection of amino acids in the room-temperature residue of an interstellar ice analogue that was ultraviolet-irradiated in a high vacuum at 12 K. We identified 16 amino acids; the chiral ones showed enantiomeric separation. Some of the identified amino acids are also found in meteorites. Our results demonstrate that the spontaneous generation of amino acids in the interstellar medium is possible, supporting the suggestion that prebiotic molecules could have been delivered to the early Earth by cometary dust, meteorites or interplanetary dust particles.

By co-depositing a gas mixture of simple carbon- and nitrogen-containing molecules with water on a 10 K surface and exposing it to ultraviolet radiation, we were able to form a residue. This residue was then placed aboard the EURECA satellite behind a magnesium fluoride window and exposed to solar radiation for 4 months before it was returned and analyzed. The resulting residue is believed to simulate the photoprocessing of organic dust mantles in the interstellar medium. Mass spectrometry indicated that the photoprocessing created a rich mixture of polycyclic aromatic hydrocarbons (PAHs) and other conjugated organic molecules, which may explain how PAHs are replenished in space.