Âé¶¹ÒùÔº

February 18, 2025

Why we think Theia existed

Credit: CC0 Public Domain
× close
Credit: CC0 Public Domain

The giant-impact hypothesis posits that billions of years ago a Mars-sized body named Theia collided with the early Earth.

The immense energy from this impact not only significantly altered Earth's rotational dynamics but also resulted in debris being ejected into space. Over time, this debris coalesced to form the Moon.

We do not know for sure if Theia existed and if it collided with the young proto-Earth, but the evidence is compelling.

For one, we are the only rocky planet with a substantial . Mercury and Venus have none, while Mars lays claim to only two small, captured asteroids. The very existence of our large moon demands explanation.

Second, there's spin. The Earth spins much faster than the other rocky planets, and the Moon orbits around us at a surprisingly swift pace. Something deep in our past must have provided all that energy, and a collision with another protoplanet explains it with ease.

Lastly, we have an unexpected piece of evidence from our human adventures to the Moon. The Apollo missions were more than pursuits of glory; they were scientific enterprises. Trained by expert geologists, the Apollo astronauts, beginning with Armstrong and Aldrin, where taught to search for and extract interesting findings.

What they returned to Earth revealed an enormous wealth of scientific knowledge of the Moon's composition, because for the first time we were able to acquire large amounts of —the generic term for the loose material that makes up the —and return it to Earth for further study. All told, the six successful Apollo missions brought back 2,200 samples totaling almost 400 kilograms of material.

The regolith returned by the Apollo missions displayed a remarkable property: the lunar surface is oddly similar in constitution to the Earth's crust, with similar ratios of elements. The only conclusion is that we must have a common origin.

So while we are never able to turn the clock back and witness the formation of the Earth and Moon, we can use the clues scattered around us to help us understand this cataclysmic event that took place over four billion years ago.

Provided by Universe Today

Load comments (0)

This article has been reviewed according to Science X's and . have highlighted the following attributes while ensuring the content's credibility:

fact-checked
trusted source
proofread

Get Instant Summarized Text (GIST)

The giant-impact hypothesis suggests a Mars-sized body, Theia, collided with early Earth, leading to the Moon's formation from the resulting debris. Earth's unique large moon, its rapid spin, and the Moon's swift orbit support this theory. Apollo missions revealed lunar regolith with a composition similar to Earth's crust, indicating a shared origin. These findings collectively suggest a significant collision event in Earth's past.

This summary was automatically generated using LLM.