How the Moon’s Origins Challenge Planet Formation Theories

By | 22/01/2025

The Moon holds key clues about how Earth and the other inner planets of the Solar System formed. Scientists debate two main theories of planet formation: slow, chaotic growth from planetesimal collisions, or rapid growth by accumulating tiny particles called pebbles. This study explores whether the Moon’s formation can help decide between these two ideas.

  1. The Moon-Forming Collision:
    The most widely accepted idea is that the Moon formed when a Mars-sized body, called Theia, collided with the early Earth. This massive impact created debris that eventually coalesced into the Moon. But for this to happen, the timing, angle, and speed of the collision needed to be just right.
  2. Testing the Pebble Accretion Theory:
    In the pebble accretion model, planets grow quickly by pulling in a steady stream of tiny particles. However, this process makes it extremely rare (less than 1 in 1,000 chances) for the Earth-Theia collision to occur under the perfect conditions needed to form the Moon. Additionally, the pebble model predicts that Earth and the Moon would have nearly identical compositions, which conflicts with observations showing subtle but significant differences.
  3. Chaotic Growth Fits Better:
    The alternative theory, where planets form through a series of slow, chaotic collisions between larger bodies, seems to align better with what we see in the Earth-Moon system. This process allows for variations in composition and makes the Moon-forming impact more likely.

Understanding the Moon’s formation isn’t just about our nearest neighbour—it sheds light on how the inner planets, including Earth, came to be. The results suggest that chaotic collisions, rather than smooth pebble accretion, played a bigger role in shaping the inner Solar System.

  • Could other moons in the Solar System provide similar clues about their parent planets’ histories?
  • How common are Moon-like collisions in other planetary systems?
  • What do these findings mean for the broader theory of planet formation?

By unravelling the Moon’s story, scientists hope to better understand the processes that created not just Earth, but the countless other rocky worlds scattered throughout the galaxy.

 

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.