includes cultured and uncultured organisms retrieved from different environments within the desert between 1984 and 2016. These organisms are distributed in bacterial, archaeal or eukaryotic domains, along with those that are unclassified taxonomically. The initial prototype of the Atacama Database includes a basic search and taxonomic and advanced search tools to allow identification and comparison of microbial populations, and space distribution within this biome. A geolocation search was implemented to visualise the microbial diversity of the ecological niches defined by sectors and extract general information of the sampling sites. This effort will aid understanding of the microbial ecology of the desert, microbial population dynamics, seasonal behaviour, impact of climate change over time, and reveal further biotechnological applications of these microorganisms. The Atacama Database is freely available at: https://www.atacamadb.cl.

Cordova-Gonzalez, A., Birgel, D., Kappler, A., Peckmann, J., 2020. Carbon stable isotope patterns of cyclic terpenoids: A comparison of cultured alkaliphilic aerobic methanotrophic bacteria and methane-seep environments. Organic Geochemistry 139, 103940.

http://www.sciencedirect.com/science/article/pii/S0146638019301779 Aerobic methanotrophic bacteria are known to synthesize a variety of cyclic terpenoids which are typified by 13 C-depleted, methane-derived carbon. This peculiarity facilitates identification of methanotroph biomarkers in natural samples. However, the current biomarker database does not always allow biomarker patterns of marine samples to be assigned to the different types of aerobic methanotrophs. To overcome this shortcoming, the carbon stable isotope composition of cyclic terpenoids of two strains of the Type I methanotroph genus Methylomicrobium was analyzed. Other than aerobic methanotrophs used for biomarker studies in the past, these two strains deriving from soda lake environments are able to tolerate the conditions typifying marine environments including high alkalinity and salinity. The cyclic terpenoid inventory of the two strains comprises 4-methyl steroids, 3-methyl- and desmethyl bacteriohopanepolyols (aminotetrol and aminotriol), and 13 tetrahymanol, all of which are C-depleted. The average carbon isotope fractionation between methane and the 13 M. kenyense M. alcaliphilum respective lipid (Δδ C ) is found to be -25‰ for and -16‰ for . These terpenoid-methane data shed new light on the previously reported compound and carbon stable isotope patterns of cyclic terpenoids 13 from methane-seep environments. Particularly, C-depleted tetrahymanol and gammacerane are reinterpreted as biomarkers of aerobic methanotrophic bacteria based on their occurrence in methane-seep deposits in 13 association with other biomarkers of aerobic methanotrophs. The use of δ C values of anaerobic methane- oxidizing archaea (ANME) lipids for the reconstruction of the isotopic composition of parent methane allows us 13 to calculate the Δδ C even for ancient seep environments. With this calculation, Type I and Type II terpenoid-methane methanotrophs can be discriminated, representing a new approach to better characterize past methanotrophy at seeps and possibly other marine environments.

Cours, Cours, T., Cordier, D., Seignovert, B., Maltagliati, L., Biennier, L., 2020. The 3.4 mabsorption in Titan's stratosphere: Contribution of ethane, propane, butane and complex hydrogenated organics. Icarus 339, 113571.

http://www.sciencedirect.com/science/article/pii/S0019103519303719 The complex organic chemistry harbored by the atmosphere of Titan has been investigated in depth by Cassini observations. Among them, a series of solar occultations performed by the VIMS instrument throughout the 13 ∼ years of Cassini revealed a strong absorption centered at 3.4 μm. Several molecules present in Titan's atmosphere generate spectral features in that wavelength region, but their individual contributions are difficult to disentangle. In this work, we quantify the contribution of the various mole cular species to the 3.4μm band using a radiative transfer model. Ethane and propane are significant components of the band but they are insufficient to reproduce perfectly its shape. Polycyclic Aromatic Hydrocarbons (PAHs) and more complex polyaromatic hydrocarbons like Hydrogenated Amorphous Carbons (HACs) are the most plausible candidates ∼ because they are rich in C-H bonds. PAHs signature have already been detected above 900 km, and they are recognized as precursors of aerosol particles. High similarities between individual spectra impede the derivation of abundances.