Triton Haze Analogs: The Role of Carbon Monoxide in Haze Formation

Triton is the largest moon of the Neptune system and possesses a thin nitrogen atmosphere with trace amounts of carbon monoxide and methane, making it of similar composition to that of the dwarf planet Pluto. Like Pluto and Saturn\u27s moon Titan, Triton has a haze layer thought to be composed of organics formed through photochemistry. Here, we perform atmospheric chamber experiments of 0.5% CO and 0.2% CH4 in N2 at 90 K and 1 mbar to generate Triton haze analogs. We then characterize the physical and chemical properties of these particles. We measure their production rate, their bulk composition with combustion analysis, their molecular composition with very high resolution mass spectrometry, and their transmission and reflectance from the optical to the near-infrared with Fourier Transform Infrared (FTIR) Spectroscopy. We compare these properties to existing measurements of Triton\u27s tenuous atmosphere and surface, as well as contextualize these results in view of all the small, hazy, nitrogen-rich worlds of our solar system. We find that carbon monoxide present at greater mixing ratios than methane in the atmosphere can lead to significantly oxygen- and nitrogen-rich haze materials. These Triton haze analogs have clear observable signatures in their near-infrared spectra, which may help us differentiate the mechanisms behind haze formation processes across diverse solar system bodies

Identification of Ammonium Salts on Comet 67P/C-G Surface from Infrared VIRTIS/Rosetta Data Based on Laboratory Experiments. Implications and Perspectives

The nucleus of comet 67P/Churyumov-Gerasimenko exhibits a broad spectral reflectance feature around 3.2 $\mu$m, which is omnipresent in all spectra of the surface, and whose attribution has remained elusive since its discovery. Based on laboratory experiments, we have shown that most of this absorption feature is due to ammonium (NH4+) salts mixed with the dark surface material. The depth of the band is compatible with semi-volatile ammonium salts being a major reservoir of nitrogen in the comet, which could dominate over refractory organic matter and volatile species. These salts may thus represent the long-sought reservoir of nitrogen in comets, possibly bringing their nitrogen-to-carbon ratio in agreement with the solar value. Moreover, the reflectance spectra of several asteroids are compatible with the presence of NH4+ salts at their surfaces. The presence of such salts, and other NH4+-bearing compounds on asteroids, comets, and possibly in proto-stellar environments, suggests that NH4+ may be a tracer of the incorporation and transformation of nitrogen in ices, minerals and organics, at different phases of the formation of the Solar System

AQUEOUS ALTERATION ON ASTEROIDS SIMPLIFIES SOLUBLE ORGANIC MATTER MIXTURES

International audienceBiologically relevant abiotic extraterrestrial soluble organic matter (SOM) has been widely investigated to study the origin of life and the chemical evolution of protoplanetary disks. Synthesis of biologically relevant organics, in particular, seems to require aqueous environments in the early solar system. However, SOM in primitive meteorites includes numerous chemical species besides the biologically relevant ones and the reaction mechanisms that comprehensively explain the complex nature of SOM are unknown. Besides, the initial reactants, which formed before asteroid accretion, were uncharacterized. We examined the mass-distribution of SOM extracted from three distinct Tagish Lake meteorite fragments, which exhibit different degrees of aqueous alteration though they originated from a single asteroid. We report that mass-distributions of SOM in the primordial fragments are well fit by the Schulz-Zimm (SZ) model for the molecular weight distribution patterns found in chain-growth polymerization experiments. Also, the distribution patterns diverge further from SZ with increasing degrees of aqueous alteration. These observations imply that the complex nature of the primordial SOM 1) was established before severe alteration on the asteroid, 2) possibly existed before parent body accretion, and 3) later became simplified on the asteroid. Therefore, aqueous reactions on asteroids are not required conditions for cultivating complex SOM. Furthermore, we found that overall H/C ratios of SOM decrease with increasing of aqueous alteration, and the estimate of H loss from the SOM is 10-30%. Organics seem to be a significant H2 source that may have caused subsequent chemical reactions in the Tagish Lake meteorite parent body

Orbitrap mass spectrometry of synthetic (exo-)planetary organic haze

International audienceOrganic hazes are present in every planetary atmosphere and impact the radiation budget as well as the planet's habitability. Producing laboratory analogs (tholins) is currently the only way to determine their physical and chemical properties. Infrared spectroscopy is not sensitive enough to characterise the incorporation of oxygen in complex nitrogen-rich samples. Very high-resolution mass spectrometry reveals that oxygen is incorporated in the tholins at the expense of nitrogen without impacting their overall unsaturation and that prebiotic molecules can be formed in planetary atmospheres. Future space missions must embark a CosmOrbitrap to characterise the aerosols in situ

Molecular screening with liquid chromatography coupled to ultra-high resolution mass spectrometry: Chromatographic methods and data treatment for application to complex organic matter in astrophysical materials

International audienceLiquid and gas chromatography have been extensively applied to the analysis of extraterrestrial materials and their analogues. Methods are often highly specific and to obtain the largest possible description of a given sample, it must be analyzed over dozens of analytical methods and instruments, often requiring some heavy sample preparation. Distributed under a Creative Commons Attribution | 4.0 International licence 2 However, because meteorites and analogue samples are usually available in relatively small quantities, their characterization requires an analytical method that can reveal their complex organic content, being their stoichiometric diversity or their isomeric variety, in one single run. This article presents two liquid chromatography methods coupled to ultra-high resolution mass spectrometry (LC-HRMS) for the screening of organic matter in astrophysical samples. The liquid chromatography methods rely on orthogonal separations on a unique hydrophilic interaction liquid chromatography (HILIC) column using two different pH and both polarities. We developed our analytical methods using a laboratory-produced mixture of complex organics simulating the photochemical haze in a super-Earth atmosphere and processed the data with custom software. The soluble fraction of only 0.2 mg of sample is used for analysis without further treatments or extraction steps. 1,160 peaks (50 < m/z < 300) have been efficiently separated, detected, and attributed to a CHNO molecular formula. Our results demonstrate the relevance of our methodology for the untargeted analysis of precious astrophysical samples returned by current and future space missions (Hayabusa2, OSIRIS-REx, MMX, MSR)

Micrometeorites soluble organic mixture analysed by Nanospray Ion Source Orbitrap mass spectrometry

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Micrometeorites soluble organic mixture analysed by Nanospray Ion Source Orbitrap mass spectrometry

International audienc

Enhancing data acquisition for the analysis of complex organic matter in direct‐infusion Orbitrap mass spectrometry using micro-scans

International audienceRationaleAcquisition quality in analytical science is key to obtaining optimal data from a sample. In very high‐resolution mass spectrometry, quality is driven by the optimization of multiple parameters, including the use of scans and micro‐scans (or transients) for performing a Fourier transformation.MethodsThirty‐nine mass spectra of a single synthesized complex sample were acquired using various numbers of scans and micro‐scans determined through a simple experimental design. An electrospray ionization source coupled with an LTQ Orbitrap XL™ mass spectrometer was used, and acquisition was performed using a single mass range. All the resulting spectra were treated in the same way to enable comparisons of assigned stoichiometric formulae between acquisitions.ResultsConverting the number of scans into micro‐scans enhances signal quality by lowering noise and reducing artifacts. This modification also increases the number of attributed stoichiometric formulae for an equivalent acquisition time, giving access to a larger molecular diversity for the analyzed complex sample.ConclusionsFor complex samples, the use of long acquisition times leads to optimal data quality, and the use of micro‐scans instead of scans‐only maximizes the number of attributed stoichiometric formulae

Micrometeorites soluble organic mixture analysed by Nanospray Ion Source Orbitrap mass spectrometry

International audienc

Orbitrap mass spectrometry of synthetic exoplanetary particles

International audienceThis work presents ESI-Orbitrap mass spectrometry results of synthetic exoplanetary organic aerosols. The diversity of detected stoichiometric formulas in samples reveals some major difference into the nitrogen and oxygen incorporation, strongly correlated with the initial gas mix composition and especially with the carbon and oxygen elemental content. These results will lead to the determination of the most favorable atmospheric composition for the formation of prebiotic molecules and will help select good exoplanets candidates for a complete caracterisation of their atmosphere with new generations of telescopes