Abiotic chemical routes towards the phosphine synthesis in the atmosphere of Venus
- 1J. Heyrovský Institute of Physical Chemistry of the CAS, v. v. i., Department of Spectroscopy, Czechia (martin.ferus@jh-inst.cas.cz)
- 2National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czechia.
- 3Institute for Chemical-Physical Processes, Italian National Research Council(IPCF-CNR), Messina, Italy
- 4University of Cambridge, Department of Earth Sciences, Downing Street, Cambridge CB2 3EQ, United Kingdom
Several of the Venera, Vega and Pioneer probe data as well as ground based observation support the presence of so-called Redox Disequilibrium Pairs (RDPs) in atmosphere of so hostile world as Venus (Greaves 2021). State of the art chemical networks cannot explain origin of an important RDP, phosphine, in oxidized atmosphere of Venus by a conventional processes (Bains 2021). We used the hybrid Density Functional Theory (DFT) for investigation of a series of chemical reaction pathways leading to the reduction of phosphate monoxide to phosphine. Our calculations indicated that a reaction network similar to photochemical synthesis of methane from carbon monoxide over acidic surfaces suggested for Mars (Civiš 2019) can also occur in clouds of Venus. As a seminal step, we have explored – via state-of-the-art quantum-based calculations – the a priori energetic feasibility of the following reaction:
HCO(radical) + PO = CO2 + PH (biradical).
Our calculations have shown that chemical conversion is constituted of three steps. Two of them are energetically favoured, however, the final conversion to phosphine is hardened by a significant activation barrier. This barrier can be overcome by a reaction of OPH radical with hydrogen radical. For assessing the potential of the newly introduced reaction mechanisms, models of the Venus and early Earth atmospheres in ARGO code and modified STAND chemical network were created and verified. Comparison of reaction yields suggests that this pathway is potentially effective enough and could be the source of phosphine recently discovered on Venus.
We acknowledge the support provided by the Czech Science Foundation within the project reg. no. 21-11366S and by ERDF/ESF "Centre of Advanced Applied Sciences" (No. CZ.02.1.01/0.0/0.0/16_019/0000778). We acknowledge support of the Czech Academy of Sciences, Strategy AV21, project VP16. The Czech team is part of the VenSpec-H Consortium onboard the ESA EnVision mission.
References:
Civiš S. et al.: Formation of Methane and (Per)Chlorates on Mars. ACS Earth Space Chem. 2019, 3, 2, 221–232.
Bains W. et al.: Phosphine on Venus Cannot Be Explained by Conventional Processes. Astrobiology 2021, 10 (21), 1277-1304.
Greaves J. S. et al.: Phosphine gas in the cloud decks of Venus. Nature Astronomy 2021, 5, 655–664.
How to cite: Ferus, M., Cassone, G., Rimmer, P., Saija, F., Mráziková, K., Knížek, A., and Civiš, S.: Abiotic chemical routes towards the phosphine synthesis in the atmosphere of Venus, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-198, https://doi.org/10.5194/epsc2022-198, 2022.
