How did collisions help Earth grow during its early formation?

Collisions were fundamental to Earth's growth through a process known as accretion. During the early history of the solar system, dust and gas condensed into small fragments that aggregated into planetesimals—the building blocks of planets.123

As these planetesimals collided and merged, their mass increased, which in turn strengthened their gravitational pull. This allowed the growing Earth to sweep up even more material, including rocky and metallic fragments, until it reached its current size.13

These impacts also played a critical role in shaping the planet's internal and surface environment:

• Internal Heating: The energy from these collisions, combined with the sinking of dense metallic elements to form the core, generated intense heat that caused the planet to partially melt.43
• Surface Modification: Frequent bombardment created craters and basins, while also delivering essential materials like water.35
• Moon Formation: A massive, glancing collision with a Mars-sized body is widely believed to have ejected material from Earth's mantle that eventually coalesced to form the Moon.45