Heuristic Approach to Understanding the Accumulation Process in Hydrothermal Pores

Abstract

Abstract:One of the central questions of humankind is: which chemical and physical conditions are necessary to make life possible? In this "origin-of-life" context, formamide plays an important role, because it has been demonstrated that prebiotic molecules can be synthesized from concentrated formamide solutions. Recently, it could be shown, using finite-element calculations combining thermophoresis and convection processes in hydrothermal pores, that sufficiently high formamide concentrations could be accumulated to form prebiotic molecules (Niether et al. (2016)). Depending on the initial formamide concentration, the aspect ratio of the pores, and the ambient temperature, formamide concentrations up to 85 wt % could be reached. The stationary calculations show an effective accumulation, only if the aspect ratio is above a certain threshold, and the corresponding transient studies display a sudden increase of the accumulation after a certain time. Neither of the observations were explained. In this work, we derive a simple heuristic model, which explains both phenomena. The physical idea of the approach is a comparison of the time to reach the top of the pore with the time to cross from the convective upstream towards the convective downstream. If the time to reach the top of the pore is shorter than the crossing time, the formamide molecules are flushed out of the pore. If the time is long enough, the formamide molecules can reach the downstream and accumulate at the bottom of the pore. Analysing the optimal aspect ratio as function of concentration, we find that, at a weight fraction of w = 0.5, a minimal pore height is required for effective accumulation. At the same concentration, the transient calculations show a maximum of the accumulation rate.

Geological and Geochemical Constraints on the Origin and Evolution of Life

“…At first glance, formamide is miscible with water and readily diluted. However, fine pores at hydrothermal vents appear to be able to concentrate formamide from dilute solutions (Niether et al, 2016;Niether and Wiegand, 2017). In addition, formamide enters the interlayer of clays under laboratory conditions (e.g., Joussein et al, 2005).…”

Improving industrial pipeline transport using research of regularities of flow of mixtures in material pipeline

“…sequential change in regular and temporary time states of motion (the processes of formation and destruction of structures, transitions of laminar flow into the turbulent one and vice versa). Under certain conditions in pneumatic conveying pipeline there emerge ordered structures and forms of motion of the originally disordered, irregular forms without special ordering external influences on the system [21][22][23].…”

“…Adoption of the basic postulates of synergy [21][22][23][24]: relative degree of state order in open systems, helping to distinguish the "order" from the "chaos"; criterion of the degree of chaos or order K -entropy (entropy of Krylov-Kolmogorov-Sinay), Lyapunov exponents, Boltzmann-Gibbs-Shannon entropy (H -Boltzmann's theorem of thermal equilibrium, S-theorem); adoption of entropy differences as Lyapunov function, and adoption of the fact that the laminar flow accepted as a state of chaos is unstable; entropy production principle -the system is moving towards reducing entropy production; turbulent flow is more ordered than laminar flow; by the criterion of S-theorem transition from laminar flow to the turbulent one is a process of self-organization; establishing new macroscopic relations among individual areas and significant complication of the structure suggest that constantly occurring nonequilibrium phase transitions in pneumatic conveying pipeline are carried out according to ↔ O C (order ↔ chaos), i. e. under the scheme of self-organization.…”

A Universal Geochemical Scenario for Formamide Condensation and Prebiotic Chemistry

“…[28] In the case of sulfur-containing minerals, sulfur-copper-iron minerals are generally more active than simple pyrite and pyrrhotine, pyrite being more effectivet han pyrrhotine (Table 1, entries 10-17). [29] Again, in the case of borates,t he so called hydrates containing hydroxyl groups (group A, Dana's classification), and anhydrous borates (groupB,D ana's classification), are more efficient in the formation of nucleobases than borosilicatesa nd borocarbonates ( Table 1, entries [22][23][24][25][26][27][28][29]. [30] Finally,t he NH 2 CHO condensation works well also in the presence of water,t hermalw ater being ar eaction medium better than sea water when the condensation is performed in the presence of the same type of miner-RaffaeleS aladino is President of the Italian Society of Astrobiology.…”

“…Formamide has in particular shown its versatility [20] owing to the mentioned ubiquity and to its facile formation and possibility of concentration. [21,22] The geochemicals cenario taken into consideration has been chosen based on its geochemicall ikelihood and its evidencebased consistence. This scenario has been experimentally challengedw ith NH 2 COH synthetic properties (as described below), because of its widespread presence andthe experimentally ob-served flexibility of its chemistry.T his approach does not exclude the eventual integration with the possible contribution of other reactants as HCN and/orH COOH.…”