Moon formed from meteorite impact

Until recently, scientists have known relatively little about the formation of our moon. However, new research by the University of Maryland brings light to this mystery and, in doing so, greatly expands humankind’s understanding of the universe.

The article, published in Nature earlier this month, further explains earlier theories on the moon’s formation by comparing the chemical composition of the Earth and the moon, using the presence of tungsten.

For the past few decades, the widely accepted theory has been that about 150 million years after the creation of the solar system, a large body named Theia, approximately the size of Mars, collided with the Earth and sent a large cloud of debris into space. Over time, the forces of gravity condensed this cloud into the moon.

This theory explains the size and orbit of the moon. A few hypotheses have attempted to explain its composition, but none have been successful, and the study authors are confused by the puzzle of why the Earth and moon are so similar in terms of their isotopic fingerprints.

An isotopic fingerprint is the ratio in a material of different isotopes, which are forms of elements with different amounts of neutrons. Disparities in isotopic ratios within elements in different materials can shed light on their origins. Most scientists agree that Theia would probably have been made up of very different elements, and some of its unique isotopic patterns should have become part of the moon.

If the cloud of debris from Earth and Theia had thoroughly mixed before condensing, Theia could have had a similar chemical composition to that of Earth, or the Moon might not been formed from Theia at all, but rather from the Earth itself.

To solve this problem, geologist Richard Walker, along with his colleagues at the University of Maryland, examined the presence of tungsten in terrestrial and lunar rock samples. They knew that more meteorites have crashed into the Earth than the moon, so more meteoric material is present on the Earth. Part of the material these meteorites deposited is the element tungsten.

The scientists realized that the amount of tungsten on Earth was only higher by a very minute amount than the amount of tungsten on the moon, so it seemed likely that the two bodies started out with the same composition of elements.

Walker explained that they have only recently developed the means to measure this tiny difference, and the results that they got after doing so were exactly what they expected.

From their results they concluded that the Earth’s mantle and moon did in fact have the same isotopic composition directly after formation. They determined that the moon formed from the material released by Earth’s collision with Theia, rather than forming from material found in the Earth before its impact with Theia.

The particular meteorite impacts that the Earth and moon faced following the moon’s formation can account for the slight differences in tungsten isotopes that the researchers found between their rock samples from the two bodies. These discrepancies arose during the millions of years after the moon formed.

More research still needs to be done to explain how the moon originally formed. While the scientists found that the moon is similar to Earth, they do not understand why exactly this similarity exists, and why it’s not similar at all to Theia.

These findings may not unlock all the mysteries of the universe, — or even of the moon itself for that matter — but it adds to our current knowledge.

“This result brings us one step closer to understanding the close familial relationship between Earth and the Moon,” Walker said in a press release. “We still need to work out the details, but it’s clear that our early solar system was a very violent place.”