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

Modelling of acid-base titration curves of mineral assemblages

The modelling of acid-base titration curves of mineral assemblages was studied with respect to basic parameters of their surface sites to be obtained. The known modelling approaches, component additivity (CA) and generalized composite (GC), and three types of different assemblages (fucoidic sandstones, sedimentary rock-clay and bentonite-magnetite samples) were used. In contrary to GC-approach, application of which was without difficulties, the problem of CA-one consisted in the credibility and accessibility of the parameters characterizing the individual mineralogical components

Cesium uptake by Ca/Mg bentonite: evaluation of sorption experiments by a multicomponent two-site ion-exchange model

Cesium sorption on Czech Ca/Mg bentonite was studied using the batch technique for a wide range of both bentonite-to-water ratios (m/V) and initial concentrations of Cs. The experiments revealed non-linear pattern of cesium sorption, which was substantially influenced by the m/V. The results of the exchange reaction between added Cs+ and Mg2+, Ca2+, Na+ and K+ ions present naturally on the bentonite sorption sites enabled to determine the appropriate selectivity coefficients. The capacity of sites with higher selectivity to cesium, which is believed to be associated with the frayed-edge sites, was measured using the AgTU method.Web of Science304143442

Study of Radium Behavior in Contact With Calcium-Silicate-Hydrates

Radium-226 is an important radionuclide with respect to the long-term safety of repositories for low and intermediate-level radioactive wastes, as well as deep geological repositories for high-level radioactive waste and spent nuclear fuel. To evaluate its mobility in the engineered barrier system of a repository, the sorption of radium on calcium-silicate hydrates (CSH), which form the major hydration phases in cementitious materials, was studied. Radium sorption to CSH was found to be very fast, leading to steady-state between solid and liquid phase after less than four days. The dependency of the equilibrium distribution ratios on radium concentration, the calcium to silicon ratio in CSH, liquid to solid ratio, and temperature was investigated, and estimates of apparent activation energy, reaction enthalpy, entropy, and Gibbs energy of the sorption process were derived. Radium sorption on CSH can be described by linear isotherms with Rd values mostly in the order of 104 L/kg. Radium sorption was found to be an exothermic and spontaneous reaction probably governed by chemical reaction rather than diffusion. As expected, the presence of ethylene diamine tetraacetic acid (EDTA) at low concentrations led only to a small decrease in radium sorption, due to the strong competition of dissolved calcium for EDTA complexation. A comparison of the sorption behavior of various alkaline earth elements used as chemical analogs for radium confirmed the significant difference in the Rd values with sorption on CSH decreasing in the order Ra > Ba > Sr

Comparative study of radium and strontium behaviour in contact with cementitious materials

A comparative study of the sorption behaviour of radium and strontium was performed on various cementitiousmaterials including crushed hardened cement pastes (HCP) and concretes as well as a synthesised calcium silicatehydrate (CSH) phase.Rd values obtained for the Ra and Sr uptake on commercial cement materials were in the range of50–380 L kg-1 and 10–30 L kg-1, respectively. No significant difference between the distribution ratios of theisotopes 226Ra and 223Ra was observed in the studied liquid to solid (L/S) ratio range, although different isothermswere determined. The Rd values for Ra were found to increase with increasing L/S ratio. The cause of thiseffect is obviously the non-linearity of the sorption isotherm, here of the convex type. In contrast, Sr uptakeseemed to be largely unaffected by variation of L/S ratios; this indicates an isotherm of almost linear type.Sorption experiments with the CSH phase confirmed the distinctive differences in the sorption behaviour betweenRa and Sr as expected, with Rd values significantly higher for Ra. Similarly, the difference between realcementitious materials and the pure CSH phase was confirmed, indicating that the sorption of alkaline earthelements is mainly due to uptake by CSH.The kinetics of Ra and Sr uptake on cementitious materials were evaluated by a set of models describing thesorption in heterogeneous systems based on different rate-controlling processes. The FD (film diffusion) model inthe case of Ra, and the ID (diffusion in inert layer) model in the case of Sr provided the best fits.The influence of temperature on the kinetics of radium sorption was studied, suggesting change in the shape ofisotherm with increasing temperature. Evaluation of sorption kinetic data yielded values of the apparent activationenergy of the uptake process.Complementary through diffusion experiments using compacted crushed HCP confirmed and extended thefindings obtained by evaluation of the batch sorption experiments performed with Ra and Sr

Morphology of Meteorite Surfaces Ablated by High-Power Lasers: Review and Applications

Under controlled laboratory conditions, lasers represent a source of energy with well-defined parameters suitable for mimicking phenomena such as ablation, disintegration, and plasma formation processes that take place during the hypervelocity atmospheric entry of meteoroids. Furthermore, lasers have also been proposed for employment in future space exploration and planetary defense in a wide range of potential applications. This highlights the importance of an experimental investigation of lasers’ interaction with real samples of interplanetary matter: meteorite specimens. We summarize the results of numerous meteorite laser ablation experiments performed by several laser sources—a femtosecond Ti:Sapphire laser, the multislab ceramic Yb:YAG Bivoj laser, and the iodine laser known as PALS (Prague Asterix Laser System). The differences in the ablation spots’ morphology and their dependence on the laser parameters are examined via optical microscopy, scanning electron microscopy, and profilometry in the context of the meteorite properties and the physical characteristics of laser-induced plasma

Elemental composition, mineralogy and orbital parameters of the Porangaba meteorite

The main objective of this study is to provide data on the bulk elemental composition, mineralogy and the possible origin of the Porangaba meteorite, whose fall was observed at 17:35 UT on 9 January 2015 on several sites of the state of Sao Paulo in Brazil. The surface of the meteorite was mapped by Scanning Electron Microscopy (SEM) and optical microscopy. The mineralogy and the bulk elemental composition of the meteorite were studied using Energy-Dispersive and Wavelength-Dispersive X-ray Spectroscopy (EDS/WDS) together with Electron Back Scatter Diffraction (EBSD). The bulk elemental composition was also independently analysed by Atomic Absorption Spectrometry (AAS), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Laser Ablation ICP MS (LA ICP-MS) and Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS). Based on the available visual camera records of the Porangaba meteorite fall, its orbit was tentatively calculated, and possible candidates for the source bodies in the Solar system were proposed. We also present a laboratory simulation of a Porangaba-like (L4 Ordinary Chondrite) meteor emission spectra. These can be used as benchmark spectra for the identification of meteor rock types through their comparison with meteor spectra recorded by high-speed videocameras equipped with simple grating spectrographs.Web of Science341art. no. UNSP 11367