Chemistry And Computational Catalysis

Biography

Biography: Svatopluk Civis

Abstract

Photocatalytic reduction of carbon dioxide on montmorillonite and TiO₂ can explain the formation of reduced gases in neutral atmospheres. CH₄ and CO were produced during 365 nm UV irradiation of CO₂ in the presence of HCl. This photocatalytic reaction represents an approximate simulation of the Martian atmosphere. In the first part of this paper, rate constants, external quantum efficiencies and effectiveness of the reduction process are discussed and compared to those estimated on Mars. In the second part, subsequent reprocessing of the CO + CH₄ and N₂ containing atmosphere (with the corresponding photocatalyst still present) was exposed to shock waves induced by a high-power laser. This  simulated a high energy density event (e.g. an asteroid impact) on the surface of an early planet exposed to heavy bombardment by interplanetary matter. In the resulting mixtures, glycine and RNA canonical nucleobases were found. Therefore, this process provides an explanation for the creation of reduced gases and the subsequent formation of simple biomolecules from neutral CO₂ rich atmospheres and also for the origin of CH₄ on Mars. The aim of this work was not to ultimately proclaim that the Earth´s early atmosphere was globally reducing. Instead, evidence is presented to support the fact that the conversion of a CO₂ atmosphere to an atmosphere containing CH₄ and CO is possible. This conversion must be considered in models of initial early atmosphere transformations. Therefore, a complete pathway leading from a neutral atmosphere to the formation of nucleobases under early Earth conditions has been demonstrated. Additionally, for the first time, this pathway is discussed in relation to the conditions of Mars upon solar irradiation and upon exposure to shock waves generated by the impacts of asteroids or comets.

Seasonal variation of atmospheric pressure: CO₂ content (red), H₂O content (black) and CH₄ content (blue). Data points have been scaled to allow for visual comparison of their fits. The data were obtained by the NASA Mars Curiosity Rover and the OMEGA instrument aboard the Mars Express. Fits in the plot represent only trends in the data.