Microstructure of the Fermo meteorite

Analyses by different electron microscopy methods contribute to draw the overall picture of the microstructure of the Fermo meteorite. Phase composition obtained by Scanning Electron Microscopy (SEM) may provide useful information about the origin of previously reported phases including kamacite, taenite, troilite, enstatite, silicate particles of olivine and pyroxene groups. The morphological aspects of separate micro- and nano-structural constituents revealed by Transmission Electron Microscopy (TEM) may reflect transformations that contribute to reconstruct the events affecting the true history of the cosmic body. Achievements of very fine-grained microstructure of minerals investigated by TEM micrographs and ion milling analysis are approaching current nanotechnology efforts

Ariel – a window to the origin of life on early earth?

Is there life beyond Earth? An ideal research program would first ascertain how life on Earth began and then use this as a blueprint for its existence elsewhere. But the origin of life on Earth is still not understood, what then could be the way forward? Upcoming observations of terrestrial exoplanets provide a unique opportunity for answering this fundamental question through the study of other planetary systems. If we are able to see how physical and chemical environments similar to the early Earth evolve we open a window into our own Hadean eon, despite all information from this time being long lost from our planet’s geological record. A careful investigation of the chemistry expected on young exoplanets is therefore necessary, and the preparation of reference materials for spectroscopic observations is of paramount importance. In particular, the deduction of chemical markers identifying specific processes and features in exoplanetary environments, ideally “uniquely”. For instance, prebiotic feedstock molecules, in the form of aerosols and vapours, could be observed in transmission spectra in the near future whilst their surface deposits could be observed from reflectance spectra. The same detection methods also promise to identify particular intermediates of chemical and physical processes known to be prebiotically plausible. Is Ariel truly able to open a window to the past and answer questions concerning the origin of life on our planet and the universe? In this paper, we discuss aspects of prebiotic chemistry that will help in formulating future observational and data interpretation strategies for the Ariel mission. This paper is intended to open a discussion and motivate future detailed laboratory studies of prebiotic processes on young exoplanets and their chemical signatures

Temperature of maximum density for aqueous mixtures of three pentanol isomers

Densities of several aqueous mixtures of 2-pentanol, 3-pentanol, and 2-methyl-2-butanol in the diluted alcohol region were determined in the temperature interval (273.65–282.15) K at atmospheric pressure using the Anton Paar DSA48 vibrating tube densimeter. The variation of the temperature of maximum density with respect to that in pure water ΔT, its structural contribution ΔT, as well as the partial molar volume of the alcohol v and its excess magnitude v were calculated. It was found that ΔT decreases as the alcohol mole fraction x increases whereas ΔT increases. In both magnitudes, the values for the mixtures of 2-methyl-2-butanol were higher than those of 2-pentanol and 3-pentanol which were found very similar. The secondary or tertiary character of the alcohol seems to be the origin of such differences in complete agreement with previous findings. The slope of the v-T curve was positive over the working mole fraction interval whereas that of the v -T curve was negative, in complete agreement with the tendencies observed for the ΔT-x and ΔT-x curves, respectively. The consistency check proposed by Armitage et al. was thus once fulfilled.Peer Reviewe

Temperature of maximum density and excess thermodynamics of aqueous mixtures of methanol

In this work, we present a study of representative excess thermodynamic properties of aqueous mixtures of methanol over the complete concentration range, based on extensive computer simulation calculations. In addition to test various existing united atom model potentials, we have developed a new force-field which accurately reproduces the excess thermodynamics of this system. Moreover, we have paid particular attention to the behavior of the temperature of maximum density (TMD) in dilute methanol mixtures. The presence of a temperature of maximum density is one of the essential anomalies exhibited by water. This anomalous behavior is modified in a non-monotonous fashion by the presence of fully miscible solutes that partly disrupt the hydrogen bond network of water, such as methanol (and other short chain alcohols). In order to obtain a better insight into the phenomenology of the changes in the TMD of water induced by small amounts of methanol, we have performed a new series of experimental measurements and computer simulations using various force fields. We observe that none of the force-fields tested capture the non-monotonous concentration dependence of the TMD for highly diluted methanol solutions.Peer Reviewe