A chunk of another world is buried deep inside Earth's Moon.

Earth’s relationship with the moon, our world’s faithful companion, goes back quite extensively in history.

It all began some 3.5 billion years ago when our solar system was unrecognizable and unlike it is today. Back then, a world of approximately the same size as Mars is thought to have crashed into an early Earth, forming the foundation for the planet we see today.

Scientists maintained that not only did this alien world fuse with our planet, giving birth to a new world and probably prepping it for life, but a massive piece of the cosmic collision is though to have ended up in space, eventually sucking up surrounding debris and forming what we today know as the Moon.

The above story is part of the so-called giant-impact hypothesis where a planet called Theia crashed into Earth. The giant impact hypothesis has been the preferred explanation in the scientific world of how the planet we live on today came to be, and how we have a massive moon orbiting our world today.

However, although this theory is mostly accepted in the scientific world, evidence of such a collision was nearly nonexistent. That is, until now.

According to a recently published paper, we’ve just found traces of a chunk of Theia, buried deep inside the moon.

“This model was capable of accounting for the then-recent observations from samples returned by the Apollo missions, which included the Moon’s low iron content relative to Earth, depletion in volatiles and enrichment in refractory elements while avoiding most of the pitfalls of previous lunar origin theories,” a group of researchers from the University of New Mexico explained in their paper published in the journal Nature. Read the full story.