Formation of planet Earth in the universe
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Formation of Planet Earth: Universe and Solar System Origins
Star and Planet Formation in the Universe
Planet formation is a common outcome of star formation throughout the universe. As stars form from the gravitational collapse of gas and dust in interstellar molecular clouds, rotating disks of material—called protoplanetary disks—inevitably develop around these young stars. These disks are the birthplaces of planets, making planetary systems a widespread phenomenon in galaxies 6910.
The Solar Nebula and Early Earth Formation
The formation of Earth began within the solar nebula, a dense disk of gas and dust surrounding the young Sun. Small dust grains in the nebula stuck together, forming pebbles. These pebbles accumulated into larger bodies called planetesimals, which were about 100 kilometers in size. Over time, planetesimals collided and merged, growing into planetary embryos and eventually into full-sized planets like Earth 1237.
Accretion and Growth of Earth
Earth’s growth was a gradual process. Most of its mass was accumulated through the collision and merging of planetesimals and planetary embryos. The final stages of Earth’s formation involved giant impacts, including a major collision that is believed to have formed the Moon. During this time, Earth was extremely hot and largely molten, with a fragile early atmosphere 1237.
Chemical Composition and Volatile Delivery
Earth’s composition was shaped by both the materials it accreted and the impacts it experienced. The solid Earth likely formed from dry, enstatite chondrite-like material, while water and other volatile elements were delivered later, possibly by carbonaceous chondrite material during a period known as the "ABEL Bombardment." This two-step process—initial dry formation followed by the addition of bio-essential elements—was crucial for making Earth habitable 258.
Models and Theories of Earth’s Formation
Several models explain the details of Earth’s formation. The "Grand Tack" model, for example, describes how the migration of Jupiter influenced the distribution of material in the inner solar system, helping to create a wet Earth and a small Mars. Other models focus on the sequence of core, mantle, and crust formation, and the role of rapid, disequilibrium processes in shaping Earth’s internal structure 37.
Earth-like Planets in the Universe
Earth is not unique in its formation process. Observations show that planets, including rocky Earth-like ones, are extremely common throughout the universe. The Milky Way alone is expected to host billions of Earth-like planets, and the universe as a whole may contain around 10^20 such worlds. However, the specific conditions that made Earth habitable—such as the right mix of elements and a stable environment—may be less common 6910.
Conclusion
The formation of planet Earth was a complex, multi-stage process that began with the collapse of a molecular cloud and continued through the accretion of dust, pebbles, and planetesimals in the solar nebula. Giant impacts and the delivery of volatile elements played key roles in shaping Earth’s composition and habitability. While the processes that formed Earth are common in the universe, the exact combination of events that made Earth suitable for life may be rare.
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