Question

Describe a process that may have produced the moon. (E)

Short answer

The Giant Impact Hypothesis, or Theia Impact, suggests that the Moon was formed when a celestial body the size of Mars collided with the early Earth around 4.5 billion years ago. This massive impact ejected debris into Earth's orbit, which then formed a debris disk. Over time, the materials within this disk aggregated under the influence of gravity, eventually coalescing into a single large body, the Moon. Evidence supporting this hypothesis includes similarities in the isotopic composition of Earth and Moon rocks, the Earth-Moon system's current angular momentum, and computer simulations of the impact event.

Step-by-step solution

Introduce the Giant Impact Hypothesis

The Giant Impact Hypothesis, or Theia Impact, is a widely accepted theory regarding the formation of the Moon. According to this hypothesis, around 4.5 billion years ago, a massive celestial body - roughly the size of Mars - collided with the early Earth. This massive impact ejected huge amounts of debris into Earth's orbit.

Explain the Protagonists: The Early Earth and Theia

In this hypothesis, two celestial bodies play essential roles: the early Earth and the impactor, Theia. The early Earth was still in the process of forming and stabilizing, while Theia was an object similar in size to Mars. It is believed to have formed in the inner solar system and had a trajectory that brought it close to Earth.

Discuss Theia's Collision with Earth

When Theia came into the vicinity of Earth, the collision occurred at a glancing angle. The violent impact resulted in a massive explosion, and enormous amounts of material were ejected into space, while the core of both bodies merged.

Formation of Debris Disk

Following the impact, the debris from Earth and Theia orbited our planet, forming a ring-like structure known as a debris disk. This debris disk consisted of molten rock, solid particles, and a mixture of iron and silicate materials that eventually began to clump together under the influence of gravity.

Aggregation and Formation of the Moon

Over time, the materials within the debris disk continued to aggregate under the influence of gravity, eventually coalescing into a single large body: the Moon. The young Moon gradually cooled down and solidified, resulting in the formation of its crust. This process might have taken somewhere around 100 million years to complete.

Evidence Supporting the Giant Impact Hypothesis

Many lines of evidence support the Giant Impact Hypothesis, such as the similarities between the isotopic composition of Earth and Moon rocks, the current angular momentum of the Earth-Moon system, and the Moon's relatively small iron core. Additionally, computer simulations of the impact event have produced outcomes consistent with our current observations of the Earth-Moon system.

Key concepts

moon formation

The formation of the Moon is a fascinating aspect of our solar system's history, and the Giant Impact Hypothesis is the prominent theory that explains this phenomenon. According to this hypothesis, the Moon formed about 4.5 billion years ago.
The process began with a massive collision between the early Earth and a Mars-sized celestial body named Theia. This catastrophic event led to the ejection of debris from both celestial bodies into space. Over time, this debris, which orbited Earth, started to clump together due to gravitational forces.
Eventually, the collection of materials coalesced into a singular, large body—the Moon. It underwent a cooling phase, resulting in the solidification of its crust. This process of moon formation might have taken up to 100 million years to complete.

Theia impact

The Theia impact is a pivotal event in the Giant Impact Hypothesis, named after the hypothetical planet Theia.
Theia is thought to have been an ancient body in our solar system, approximately the size of Mars. This celestial object, likely formed in the inner solar system, followed a path that brought it dangerously close to Earth.
When Theia collided with Earth, it was not a head-on crash. Instead, a glancing impact occurred that was sufficiently energetic to cause a large-scale explosion.
The result of this collision was the merging of the two cores while ejecting vast amounts of materials into space, which later participated in forming the Moon. This impact reshaped both bodies, significantly altering their future evolutionary paths.

debris disk

Following the colossal impact between Theia and Earth, an enormous cloud of ejected material emerged, forming what is known as a debris disk. This disk of debris was filled with molten rock, iron, silicate materials, and other fragments from the collision.
The debris orbiting Earth created a ring-like structure, similar to rings seen around some other planets today.

• The particles within the debris disk started to interact with one another, gradually coalescing due to gravitational attraction.
• Over time, these interactions resulted in the aggregation of material, forming larger and larger clumps.
• Eventually, this process of accretion led to the formation of the Moon with its recognizable spherical shape.

This crucial step in the Giant Impact Hypothesis helped describe how the mass and distribution of debris eventually gave rise to our Earth's only natural satellite.

Earth-Moon system

The Earth-Moon system is a unique and complex astronomical pairing that offers insights into the solar system's evolution.
The Giant Impact Hypothesis not only explains how the Moon was formed but also illuminates the relationship between Earth and its Moon. After the impact and the eventual formation of the Moon, Earth retained its vastly enhanced core, while the Moon acquired its relatively small core.

• One significant outcome of this historical event is the current angular momentum of the Earth-Moon system.
• Due to the impact's effects, Earth and Moon have become tidally locked, explaining why we only see one side of the Moon from Earth.
• The isotopic similarities found in Earth and Moon rocks further support the idea that they originated from the same event.

These shared characteristics underscore the importance of the Giant Impact Hypothesis in understanding how the Earth-Moon system formed and evolved over billions of years.