13 Mar 2019

William commented, mainstream doesn't mind catastrophism as long as it happened eons ago. See Elements volume 15:1 (February) which is a special issue devoted to the planet Mercury. Charlier and Namur, 'The Origins and Differentiation of Planet Mercury' (2019) page 9-14. Excerpts picked out by William are (page 9), metal enrichment may originate from primordial processes in the solar nebula or from a giant impact that stripped most of the silicate portion of a larger planet leaving Mercury as we know it today.

page 13 ... collisional stripping and inefficient accretion - the high metal/ silicate ratio of Mercury could have been inherited during collisional processes through successive impacts that might have been responsible for rapid collisional stripping of the silicate portion of the planet (quoting Benz et al 1988). This process is also referred to as collisional or cratering erosion, and a range of such impact-related scenarios has been considered (Asphaug and Reufer, 2014). One or more head-on or 'hit and run' collisions (with a range of possible impact parameters, such as the velocity and relative size and mass of target and impactor, and the impact angle) between proto-Mercury and another body or bodies would be responsible for the ejection of material from the outer silicate portion of the planet. This ejecta cloud would not subsequently re-accrete, meaning that such a collision would affect the whole volume of the planet to leave a metal rich core and a smaller silicate outer portion. Velikovsky did not actually visualise a collision between a rogue body and planet Earth, in spite of the title of his book, but contemplated on a near miss. This was regarded as anathema to mainstream, heretical even, and his work was subsequently cast into the outer regions of science. It seems like some authors nowadays are coming out of the outer regions, like a bat on a dark night, and floating all kinds of collisional ideas. Times are a changing.