Giant Impacts Can Dramatically Lower the Internal Pressure of Planets

The internal pressure of planets can be dramatically be lowered due to giant impacts, according to a study by Caltech. This finding could significantly change the current model of planetary formation.
The impacts, such as the one that is thought to have caused the formation of the earth's moon roughly 4.5 billion years ago, could cause random fluctuations in core and mantle pressures that would explain some puzzling geochemical signatures in Earth’s mantle.
"Previous studies have incorrectly assumed that a planet's internal pressure is simply a function of the mass of the planet, and so it increases continuously as the planet grows. What we've shown is that the pressure can temporarily change after a major impact, followed by a longer term increase in pressure as the post-impact body recovers. This finding has major implications for the planet's chemical structure and subsequent evolution," says Simon Lock, postdoctoral researcher at Caltech and lead author of a paper explaining the new model that was published by Science Advances on September 4.
Lock authored the paper with colleague Sarah Stewart (PhD '02), professor of planetary science at the University of California, Davis, a 2018 MacArthur Fellow, and an alumna of the Caltech Division of Geological and Planetary Sciences.
Planetary systems typically begin as a disk of dust that slowly accretes into rocky bodies. The end of the main stage of this process is characterized by high-energy collisions between planet-sized bodies as they coalesce to form the final planets.

Source: Caltech.edu