Earth's greatest mystery: How was the Moon born?

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The Moon is visible in the sky every day, yet one of the greatest astronomical mysteries still surrounds it: how did it get into orbit around Earth? Scientific theories and recent discoveries shed light on the fact that our satellite is not just a celestial spectacle, but also fundamentally important for life.

The latest episode of the Márkopédia series on the PamKutya YouTube channel examines various theories regarding the Moon's origin, from old, discarded hypotheses to the most currently accepted catastrophic scenario.

Discarded Theories: The Path of Scientific Progress

In the research on the Moon's origin, several theories emerged that were later refuted in light of modern scientific evidence:

1. The Fission Theory

This was one of the earliest ideas, suggesting that the young, molten, and rapidly spinning Earth simply tore off a massive piece. Some even hypothesized that the Pacific Ocean basin was the "scar" it left behind. The theory has since been refuted: Earth never spun fast enough for this to occur, and geological data does not support the role of the oceanic basin.

2. The Capture Theory

According to this, the Moon formed elsewhere in the Solar System and, traveling alone, came too close to Earth, whose gravity finally captured it. However, astronomical simulations show that the chance of this happening is minute. It would have been far more likely for the celestial body to either collide head-on or be slingshotted into a different trajectory.

3. The Co-formation Theory

This theory posited that Earth and the Moon were actually twin planets that formed simultaneously from the same materials. Chemical evidence overturned this idea, as the Moon has a proportionally much smaller iron core than Earth, suggesting a different formation process.

The Dominant Hypothesis: The Giant Impact

The theory most widely accepted by scientists today is the Giant Impact Hypothesis, often referred to as the Giant Splash or Theia Impact.

The Catastrophic Scenario

The currently accepted view holds that 4.5 billion years ago, a Mars-sized planet, which researchers named Theia, struck the young Earth at an oblique angle.

1. Collision and Ejection: The immense energy of the collision melted part of the Earth and blasted a huge amount of debris into space, which formed an incandescent ring around the Earth.

2. The Birth of the Moon: Over time, this debris coalesced under gravity, creating the Moon we know today.

   
   

This theory successfully explains Earth's current rotational speed, as well as why the Moon has a small iron core (Theia's iron-rich core merged with Earth's). Furthermore, the extreme heat of the impact evaporated water, explaining the dryness of the lunar rocks.

The Isotope Mystery: Questions Reopened

Although the Giant Impact theory explained many things, the lunar rocks brought back to Earth during the Apollo program raised a new set of issues.

Near-Perfect Isotope Match

When scientists analyzed the 382 kg of rock collected by the Apollo astronauts, they made a shocking discovery: the Moon's chemical isotope composition is almost identical to that of Earth.

This is problematic because the original simulations predicted that the Moon should primarily consist of material from the impacting body, Theia. The isotope match, however, suggests that the Moon formed almost entirely from Earth's material.

Newer Theories

To resolve this contradiction, scientists are working on new, modified theories:

• Complete Mixing: The impact was so massive that the material of both planets completely mixed, and the Moon formed from this homogenized material.

• Deep Merger: Theia's core fully merged into Earth, and only Earth's outer layers were ejected.

• Multiple Smaller Impacts: Not one single giant impact occurred, but a series of smaller impacts over millions of years that ejected larger quantities of Earth's material.

The Moon: The Guarantee of Life

Regardless of which theory ultimately proves true, the Moon's role in the existence of life on Earth is undeniably fundamental.

• Stabilizing Earth's Axis: The Moon's gravitational pull stabilizes Earth's axial tilt of 23.4 degrees. Without the Moon, this tilt would wobble chaotically, resulting in extreme, unpredictable climates and seasons—or their complete absence.

• Lengthening the Days: The tidal phenomenon also affects Earth's rotation: the movement of the oceans has slowed the planet's spin over billions of years. Without the Moon, a day would only be about 10 hours long, accompanied by constant super-hurricanes.

• Life's Springboard: Many scientists believe that the tidal phenomenon was a key catalyst in helping marine life adapt to the rhythmic meeting of water and land, thereby facilitating the transition of life onto land.

  
  

In summary, it is no exaggeration to state that life as we know it on Earth owes its existence to the Moon, and thus fully understanding its origin is a noble scientific goal.