<div> <p><strong>&#160;Introduction: </strong>Sugars are important molecules with high biological interest. Found in cometary-like analogs (Meinert et al., 2016), carbonaceous meteorites (Cooper et al., 2001; Furukawa et al., 2019), and likely on early Earth, sugars may have contributed as a source of molecules for the emergence of prebiotic systems on Earth. Hence, it is of prime importance to investigate their formation in conditions relevant to these environments, and particularly in the presence of minerals. For example, sugar formation is achieved through the formose reaction: the dimerization of formaldehyde, forming glycolaldehyde, which then by aldol reactions with another formaldehyde, will form successively higher sugar homologues. A catalyst is usually required for the first step, the formation of glycolaldehyde (typically calcium hydroxide). However, there is a lack of studies exploring the potential of minerals on the classical formose reaction (Gabel and Ponnamperuma, 1967; Haas et al., 2020) and in conditions representative of prebiotic environments. Here, we focus on the formation of sugars from formaldehyde <em>via</em> the formose reaction in aqueous solution using minerals, simulating conditions in which planetary surfaces could have evolved at the beginning of the Solar System.</p> <p><strong>Experiments and methods:</strong> Experiments took place in aqueous systems under anoxic atmosphere at 80&#160;&#176;C. We choose olivine as a model silicate, which is omnipresent in the solar system, and designed a series of experiments differing formaldehyde (F), glycolaldehyde (G), calcium hydroxide Ca(OH)<sub>2</sub> (&#945;) and olivine (O) compositions. We tested different combinations, O, F, FO, FG, FGO, F&#945;, FG&#945;, for different durations up to 45 days. Formaldehyde (under the form of polyoxymethylene) was introduced with glycolaldehyde or calcium hydroxide at a weight ratio of 10/1 and olivine/formaldehyde also at a weight ratio of 10/1. The mixtures were loaded in closed cells under argon atmosphere in a glove box before being heated in an oven at 80 &#176;C. We used Gas Chromatography-Mass Spectrometry (GC-MS) and GC&#215;GC-TOFMS for the identification and quantification of sugars formed in the individual samples.</p> <p><strong>Results: </strong>Identification of sugars in the different samples was performed comparing retention times and relative mass spectra with those of reference standards (oses, polyols, sugar acids and deoxy sugars acids).</p> <p><strong><img src="" alt="" width="494" height="449" /></strong></p> <p>Abundance of sugars found in samples after 2 days of reaction are shown in figure 1.<strong> </strong>No sugars have been identified in samples F2, except minor contaminants from the derivatization protocol. In contrary, in the presence of olivine (sample FO2), 16 sugars have been identified and quantified based on reference standards, and many more peaks seen in the chromatograms are suspected polyolsbased on their mass spectra. We observed the same sugars in the FGO samples, while only a few of them are observed in the FG samples. Most importantly, olivine allowed the detection of C6 sugars after only 2 days of reaction, not observed in samples without olivine even after 45 days of hydrothermal reaction. When compared to experiments with the classical Ca(OH)<sub>2</sub> catalyst, identical sugars are identified with olivine with highest abundances found for Ca(OH)<sub>2</sub>. For all samples, the diversity and quantity of sugars (mainly oses) decreased after 2 days of reactions, and mainly polyols remained in samples with olivine after 45 days.</p> <p><strong>Discussion: </strong>These experiments demonstrate that minerals may have played a crucial role in the chemical reactivity during evolution of chemical systems in aqueous environments. Here, sugars have been formed &#160;through a mineral-assisted formose reaction leading to a high molecular diversity and sugar abundance after short reaction times, without any other classical catalyst. The silicate likely ensures the selection and stabilization of the C3-C4 sugars allowing rapid aldolisation to C6, unlike solutions without silicate. However, decomposition of sugars with time is inevitable; nonetheless, surprisingly polyol-sugars survive hydrothermal alteration with olivine on longer times. These experiments raise again the question of mineral impact on the organic evolution, even as simple as olivine, in conditions mimicking aqueous environments on planetary surfaces similar to prebiotic conditions on Earth (Vinogradoff et al., 2020).</p> <p><strong>References: </strong>&#160;&#160;Cooper G. et al., (2001), Nature 414.</p> <p>Furukawa Y. et al., (2019), Proc. Natl. Acad. Sci. 116.</p> <p>Gabel N. W. and Ponnamperuma C. (1967), Nature 216.</p> <p>Haas M. et al., (2020), Commun. Chem. 3.</p> <p>Meinert C., et al., (2016), Science 352.</p> <p>Vinogradoff V. et al., (2020) Geochim. Cosmochim. Acta 269.</p> </div> <p>&#160;</p>
<p><strong>Introduction: </strong>Meteorites, which are the remnants of our protoplanetary disk, provide a rich source of chemical information to investigate the origin of organic matter that have fallen on Earth and may have thus contributed to the emergence of life. Among meteorites, carbonaceous chondrites that contain organic matter are among the most primitive materials in the Solar System. Asuka 12236, found in Antarctica in 2012, has been classified as a member of the CM group. According to the first mineralogical analyses (Kimura et al., 2020, Nittler et al., 2021), Asuka 12236 is among the most primitive member of this group showing very few signs of aqueous alteration in its mineralogy.</p> <p>Here, we have performed an overview of the soluble organic matter (SOM) present in this primitive meteorite, and compared it with other carbonaceous chondrites of the same family group. Two types of analysis were carried out on the SOM: a non-targeted analysis and then a targeted one on the basic so-called building blocks of life such as nucleobases and amino acids.</p> <p>&#160;</p> <p><strong>Methods: </strong>At first, we measured the global carbon content of our samples by elemental analysis using two grains of 2 mg each.</p> <p>For the non-targeted high-resolution analysis of the SOM, 17 mg of the meteoritic material were used to extract the SOM with solvents allowing the preservation of meteorite organics (Schmitt-Kopplin et al. 2010). The fragment was crushed and successively extracted with dichloromethane, hexane and methanol at room temperature. The extracts were analyzed by FTICR (Fourier-Transform Ion Cyclotron Resonance) within a mass range of 150-1000 m/z.</p> <p>For the analysis of the amino acids and nucleobases, 226 mg were extracted in water for 24h at 100&#176;C. Aliquots were collected after centrifugation. Two UPLC-MS analyses have been performed (Serra et al., 2022) on these aliquots: the first was a screening from 50 to 750 m/z done with a Q-exactive Orbitrap coupled with a HILIC column. The second analysis has been done with a chiral column, allowing separation of targeted amino acids and information on a possible enantiomeric excess. &#160;This chiral analysis is coupled with UPLC- Multiple Reaction Monitoring (MRM-MS) MS analyses.</p> <p>Identification and quantification of the molecules were done by dosed addition using 54 amino acids and 5 nucleobases (Adenine, Guanine, Cytosine, Thymine, Uracil), ensuring the right identification of the isomers. &#160;Note that our protocol does not include HCl hydrolysis step of the extracts, neither a derivatization procedure.</p> <p><strong>Results and Discussion:</strong> Elemental analysis (EA) done on 2 different fragments reveal the heterogeneity of our sample, in addition to the grains analyzed by Nittler et al., 2020, likely showing different alteration degrees in the chondrite (Fig. 1). We observe a correlation of carbon and nitrogen abundances in all grains of N/C ~ 0.05. From its H content, which can be extrapolated as the quantity of water, Asuka 12236 falls near the less altered CM chondrites, relatively close to the heated ones (EET and MIL CMs) (Alexander et al., 2012), while no sign of heat above 250 &#176;C is observed on its mineralogy (Kimura et al., 2020).</p> <p><img src="" alt="" width="516" height="480" /></p> <p>Electrospray ionization in negative mode FTICR analyses of the methanol on Asuka SOM reveal a global chemical composition of C, H, N, and O molecules&#160; up to 13211 different formulae (Fig. 2).&#160; The CHONS family contains the major chemical compounds for 41 % followed with CHOS family for 34 %. Such sulfur rich compounds can be related to the high abundance of mineral sulfide observed in the Asuka matrix (Kimura et al., 2020) and found by elemental analysis (2.4 wt.%). Compared to others CMs, such as Murchison and Aguas Zarcas, measured with the same instrument, Asuka has a similar SOM diversity with more sulfur organic compounds. The Paris meteorite, also among the least altered chondrites (Marrocchi et al., 2014), has half in amount of compounds with a similar relative abundance in sulfur containing compounds as Asuka in its methanol SOM. &#160;</p> <p><img src="" alt="" width="487" height="437" /></p> <p>The UPLC-HRMS method allows a rapid screening of small polar molecules. We observe a huge diversity of small compounds (<200m/z), with more intense signals than those obtained from Aguas Zarcas (Serra et al.; 2020).</p> <p>Target analysis performed with chiral column allow the identification and quantification of roughly 40 different amino acids. None of the natural nucleobases has been firmly identified, but some masses seen by UPLC-HRMS method do correspond to possible nucleobases isomers (Ruf et al., 2019).</p> <p>Overall, our analysis results in the observation of a very diverse compounds in Asuka 12236, similar to what is observed in more aqueously altered chondrites (Murchsion and Aguas Zarcas). In agreement with Glavin et al., 2020, we confirm the high concentration and diversity of amino acids, together with the identification of new ones in our extract of the meteorite (Fig. 3).</p> <p><img src="" alt="" width="521" height="477" /></p> <p>Such diversity, in amino acids and in global molecular composition, in addition to the quite high H wt.% indicates that the OM in Asuka 12236 has likely been altered during aqueous alteration, however still less than Murchison. It is also possible that Asuka 12236 presents more than one lithology, as seen with the three different results by EA, which can be related to the CI/CM clast seen in the matrix (Nittler et al., 2021). The chemical composition of the Asuka 12236 meteorite points toward a very rich and diverse composition but still needs further investigation in comparison to other&#160;meteorites to hypothesize on its origin and possible precise degree of alteration by aqueous processes.</p> <p><strong>Aknowledgements: </strong>We thank Philippe Clayes for the Asuka 12236 sample coming from the Asuka collection retrieved by expedition in Antartica by VUB-ULB and the Royal institute of the Natural Sciences in Bruxelles.</p> <p>This study was partially funded by the Deutsche Forschungs-gemeinschaft (DFG, German Research Foundation) &#8211; Project-ID 364653263 &#8211; TRR 235 (CRC 235)</p> <p>&#160;</p> <p><strong>References:</strong></p> <p>Kimura. M. et al., (2020), Polar Science, (26), p100565.</p> <p>Marrocchi et al. (2014), Meteoritics and planetary science 49.</p> <p>Nittler et al., (2021), Meteoritics and planetary science 56</p> <p>Ruf et al., (2019). The Astrophysical Journal Letters, 887</p> <p>Schmitt-Kopplin. P. et al., (2010), PNAS, 107 (7) p 2763-2768</p> <p>Serra. C. et al., (2022), Talanta (Oxford), (243), p123324</p>
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