Lecturer: Helmut Lammer (AAS) Date: 2018-12-13 10:00 Place: Aniara
Measured noble gas and K/U ratios constrain the early evolution of Venus and Earth
Helmut Lammer
Austrian Academy of Sciences
Space Research Institute
Graz, Austria
Abstract.
The atmospheric noble gas isotope and elemental ratios onVenus and Earth provide important information on their origin and evolution. While they were still accumulating mass, these planets captured most likely H2-dominated atmospheres by accumulating gas from the circumstellar disk after the formation of the Solar System, which were then lost by impacts or planetary embryos and EUV-driven hydrodynamic escape after the disk dissipated.
In such a case isotopes with solar-abundance were embedded in the nebular gas and moderately volatile elements like potassium (K) were also released at high temperatures (1500-2500 K) from the magma ocean into the captured H2-envelope.
This hydrodynamic flow of escaping hydrogen gas dragged heavier elements with it at different rates, leading to changes in their ratios. Depending on the disk lifetime and the activity of the young Sun, it is shown that the reproduction of the observed atmospheric 36Ar/38Ar, 20Ne/22Ne, noble gas ratios and the K/U ratios for both planets can by used for estimating the masses of proto-Venus and proto-Earth at the time the nebula gas dissipated.
Created 2018-09-26 12:50:44 by Mats Holmström Last changed 2018-12-05 17:38:28 by Mats Holmström
