In this study, a chemometric strategy was developed for analysis of gas chromatographic (GC) and infrared spectroscopic (FT-IR) fingerprints of nine crude oil samples from the main oil wells of Iran to classify them and to find their origins. In this regard, a fractionation method based on saturated, aromatic, resin, and asphaltene (SARA) test was used. Then, these fractions were analyzed by GC-FID and GC-MS. Also, nine crude oil samples were analyzed by FT-IR. The obtained GC fingerprints were aligned using correlation optimized warping (COW) and auto-scaled, and then analyzed using principal component analysis (PCA) and hierarchical cluster analysis (HCA). Evaluation of PCA scores plot (explaining 89.35% of variance for two PCs) and HCA dendrogram showed that aromatic fractions belong to three classes. The clustering results of aliphatic and resin fractions also showed the presence of three clusters but with different samples due to the difference in their composition. The results of unsupervised classification were then used as a starting point for partial least squares-discriminant analysis (PLS-DA) and counter propagation-artificial neural network (CP-ANN). On the other side, FTIR fingerprints of crude oil samples were also clustered using PCA and HCA. Evaluation of PCA scores plot (explaining 95.15% of variance for two PCs) and HCA dendrogram showed that samples belong to three clusters. These initial results were used as a starting point for PLS-DA and CP-ANN. Accuracy of PLS-DA was 0.890 for calibration and 0.818 for test sets. Also, CP-ANN accuracy values were 1.000 and 0.818 for train and test sets, respectively.

Heard, A.W., Kite, E.S., 2020. A probabilistic case for a large missing carbon sink on Mars after 3.5 billion years ago. Earth and Planetary Science Letters 531, 116001.

http://www.sciencedirect.com/science/article/pii/S0012821X19306934 Mars has a thin (6 mbar) CO atmosphere currently. There is strong evidence for paleolakes and rivers formed 2 by warm climates on Mars, including after 3.5 billion years (Ga) ago, which indicates that a CO atmosphere 2 thick enough to permit a warm climate was present at these times. Since Mars no longer has a thick CO 2 atmosphere, it must have been lost. One possibility is that Martian CO was lost to space. Oxygen escape rates 2 from Mars are high enough to account for loss of a thick CO atmosphere, if CO was the main source of 2 2 escaping O. But here, using H isotope ratios, O escape calculations, and quantification of the surface O sinks on Mars, we show for the first time that O escape from Mars after 3.5 Ga must have been predominantly associated with the loss of H O, not CO , and therefore it is unlikely that ≥250 mbar Martian CO has been lost to space in 2 2 2 the last 3.5 Ga, because such results require highly unfavored O loss scenarios. It is possible that the presence of young rivers and lakes on Mars could be reconciled with limited CO loss to space if crater chronologies on 2 Mars are sufficiently incorrect that all apparently young rivers and lakes are actually older than 3.5 Ga, or if climate solutions exist for sustained runoff on Mars with atmospheric CO pressure <250 mbar. However, our 2 preferred solution to reconcile the presence of <3.5 Gya rivers and lakes on Mars with the limited potential for CO loss to space is a large, as yet undiscovered, geological C sink on Mars. 2

Heck, P.R., Greer, J., Kööp, L., Trappitsch, R., Gyngard, F., Busemann, H., Maden, C., Ávila, J.N., Davis, A.M., Wieler, R., 2020. Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide. Proceedings of the National Academy of Sciences 117, 1884.

https://doi.org/10.1073/pnas.1904573117 Significance: Dating of interstellar dust directly with astronomical methods is not possible. Neither is dating based on the decay of long-lived radioactive nuclides, due to current analytical limitations and unknown initial isotopic compositions. Here we present interstellar ages of individual presolar SiC grains from a meteorite. The ∼ ages are based on Ne isotopes produced by galactic cosmic rays. Lifetimes of 60% of our grains are <3 × 108 y, while at least 8% are >109 y, in line with what is expected for large grains. The former could be the end products of stars originating in an enhanced star formation episode. Presolar grains are the oldest datable solid samples available and provide invaluable insight into the presolar chronology of our galaxy.