Chemicals in ancient ocean rocks hint that 3.2 billion years ago, the surface of a baby Earth was continent-free and covered by a global ocean.
3 billion-year-old Earth had water everywhere, but not one continent, study suggests : Read more
"We can't really say what the source of the water is from our work, but we do suggest that whatever the source, it was present when the magma ocean was still around," Johnson told Live Science in an email."
Explaining the origin of Earth's abundant water supply using collisions and the Faint Young sun problem is always interesting. 3.2E+9 years ago, the Earth was still deep in the Faint Young Sun. 4.5E+9 years ago or perhaps a bit later, the Earth was likely suffering the synestia phase of matter, something the new computer models show for giant impacts taking place near the late stage of planetary evolution.
https://phys.org/news/2019-09-planetary-collisions-internal-pressures-planets.html ""We have no direct observations of the growth of Earth-like planets. It turns out that the physical properties of a planet can vary wildly during their growth by collisions. "
My observation, there is no direct observation of how Earth has so much abundant water today for life either.