Melting, impacts, and the volatile contents of the interiors and atmospheres of Mars and Venus

• Applicant: Dr. Thomas Ruedas
• Subject Area: Geophysics
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 398660091

Melting processes in planetary mantles have been shaping the compositional evolution of planets since their time of formation in many respects. One of the most important consequences of melting is the mobilization and redistribution of volatile trace components of the mantle, in particular water and carbon dioxide, within the mantle, between mantle and crust, and ultimately also between the interior and the atmosphere, as volatiles are outgassed during volcanic activity. Melting therefore influences not only the chemical state of the interior but plays also a crucial role in the build-up of an atmosphere and the subsequent climate evolution. The atmosphere, however, also exerts a feedback influence on the interior by controlling the efficiency of degassing via the pressure at the surface.Meteorite impacts were a major geological influence in the early evolution of the planets. Impactors of all types and sizes have both eroded and replenished the atmospheres of their target planets to different extents, and the larger ones were able to penetrate deeper into the solid planet and trigger geodynamical processes; again, melting is one of the most important of them. There is, then, a complex interplay between melting processes in general, meteorite impacts, and the atmosphere, which may put planets on quite different evolutionary paths.In the proposed project, these interactions will be studied with the help of numerical models of mantle convection, of impact dynamics, and of atmospheric evolution, which will be coupled in different ways; the algorithms that handle these tasks either exist already and will be adapted and refined or they will be developed for the purpose. The mantle convection forms the long-term framework of the evolution model and is punctuated by impacts, which appear as instantaneous perturbations; the atmosphere model acts as a boundary condition for the mantle model that is, however, not static but can evolve in its own way and in interaction with the mantle and the impacts.This composite model will be used specifically to model the evolutions of Mars and Venus, the two terrestrial bodies in our Solar System that are in many respects most similar to Earth. Among other things, it will be used to constrain the initial concentrations of water and carbon dioxide in their mantles and their redistribution, attempt a comparison with observations, and consider the dynamical consequences of the secular loss of volatiles from the interior, e.g., with regard to the formation of a stagnant lid. The atmosphere module will be used to elucidate the feedback mechanisms between outgassing and climate, in particular in cases like the escalation into high-pressure, high-temperature greenhouse conditions as on Venus. The impact module will test how decisively impacts modulated the chemical evolution of the interior and the atmosphere and whether their net effect was to deplete or feed the atmosphere.

• DFG Programme: Research Grants
• Co-Investigators: Professorin Dr. Doris Breuer; Dr. Nicola Tosi; Professor Dr. Kai Wünnemann