Boreskov

PL‐1EARTH AND PLANETS ORIGIN: HOW DO WE VIEW AND MODEL IT?Marov M.V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry RAS, Moscow, RussiaSolar system origin is regarded as a cornerstone of the planets formation and eventuallyEarth evolution towards biosphere set up. While planets birth from gas‐dust discs is quiteroutine process in our and other galaxies, solar system configuration, and specifically Earth,seems to be unique. Obviously, multiple physical and chemical processes underlied thisevent and ensured specific scenario to distinguish solar system from other planetarysystems. Understanding and reconstruction of these processes is the main goal and the greatchallenge of the planetary cosmogony. The contemporary views and further progress in thefield are supported by astronomical observations of the numerous gas‐dust discs aroundyoung solar type stars, escalating discoveries of extrasolar planets, and computer modelingof the planetary systems formation and early evolution based on the advanced theoreticalapproach and enormous advancement in computing capacity.Complex problems are addressed in the models development, data of observationplacing important constraints on the models validity. Our approach is based on heterogenicmechanics of turbulent media involving in‐depth study of disc thermodynamics on theaccretion stage from which the key cosmochemical consequences emerge. In particular weargue that because in the region of Earth‐Venus orbit temperature was not lower than 300–500 К, the reduced water‐lacking matter different from CI carbonaceous chondrites byabsence of hydrosilicates and volatiles would originated. This means that Earth and itsneighbors has born as water‐poor bodies and an other source of volatiles, probably ofexogenic nature, would require to compensate such a lack and to make possible theirhydrosphere/atmosphere appearance. Comets and asteroids impacted inner planets at thevery early stage of the solar system formation are invoked as such a plausible source.Disc dynamics is thoroughly evaluated with the involvement of dust subdisk formation inthe near‐equatorial plane and its fragmentation into dust clusters due to gravitationalinstability accompanied by the angular momentum transfer. Numerous solid bodies ofasteroid size appeared from subdisk at this early stage within the first million years aftersolar system formation – evidence that is supported by radio isotopes dating of iron andstony meteorites available as collisional fragments of these bodies which are regarded as the6