Is Earth's Moon a 'Stolen Object'?

New research has overturned the theory that the Moon was formed from debris from Earth and the planet Theia.

Astronomers Darren Williams and Michael Zugger of Pennsylvania State University (USA) have identified some new evidence that could explain the origin of the Moon , Earth's only natural satellite.

The Moon may be an object that Earth accidentally stole during the Hadean eon - (Illustration by AI: ANH THU).

According to the most widely accepted hypothesis, based on evidence of Earth–Moon material homogeneity and collisional models in the early Solar System, the Moon is the "common child" of Earth and Theia.

Theia is the name of a hypothetical planet the size of Mars, which is believed to have crashed into the early Earth about 4.5 billion years ago, at the beginning of the Hadean eon.

The collision caused the materials of the two celestial bodies to blend together, forming today's Earth. Some of the debris was thrown into Earth's orbit, gradually condensing into the Moon.

Although supported by much evidence, it remains just a hypothesis.

According to research results recently published in the scientific journal The Planetary Science Journal, another possibility has arisen: The celestial body called the Moon could be a "stolen object" like Neptune's moon Triton.

Triton orbits Neptune in the opposite direction to the other moons and at a different angle.

Scientists therefore concluded that it was an object in the Kuiper Belt on the edge of the Solar System that accidentally moved across and was trapped by Neptune's gravity.

As for Earth's Moon, there is also an unexplained anomaly: Its orbit around Earth does not align with the equator as we would expect for an object that coalesced from the debris cloud.

There are only two possible scenarios:

• One is that there is some impact that causes the orbit of this satellite to deviate.
• The second, more plausible hypothesis is that it did not coalesce from any debris cloud at all.

According to the research team's calculations, although much smaller than Neptune, our planet is still strong enough to capture an object the size of Mercury or even Mars.

That suggests it may have been stolen from Earth by something else , or simply a massive object that formed directly from the Solar System's protoplanetary disk, trapped in Earth's orbit billions of years ago.