2 what happened during Earth's "dark age" (the first 500 million years)?
It is now believed that during earth's formation, a Mars-sized planet collided with it, creating a huge cloud of debris that became earth's Moon and releasing so much heat that the entire planet melted. but little is known about how the resulting molten rock evolved during the planet's infancy into the earth we know today. the first 500 million years of earth's existence, known as the Hadean eon, is a critical missing link in understanding how the planet's atmosphere, oceans, and differentiated layers of core, mantle, and outer crust developed. Scientists have almost no idea how fast the surface environment evolved, how the transition took place, or when conditions became hospitable enough to support life. Some clues from Earth's Moon and other planets are allowing a clearer picture of the Hadean Eon to gradually emerge. The amount of information that can be extracted from even the tiniest samples of old rocks and minerals is increasing rapidly, and with concerted effort, it is expected that many more ancient rocks and mineral samples will be found.