Researchers may have pinpointed the origin of water on the moon.

Asteroids could actually be responsible for 80 percent of the liquid housed within the planet’s interior, according to a new study. Previous theories credited comets as the primary delivery mechanism for water on the planet after hydrogen atoms were discovered in moon samples six years ago.

An international team of researchers made this conclusion by analyzing the chemical composition of moon samples and then comparing them to known lists of asteroid and comet components, reported Popular Science. 

The results indicated that asteroids delivered the brunt of the lunar water an estimated 4.5 billion years ago. Comets did play a role in this process, but the scientists concluded they only contributed 20 percent or less of the water.

The scientists noted this process occurred during a period where developing celestial bodies like the Earth and other planets were hit with a staggering amount of asteroids. Also, early water composition appeared similar to samples found on the earth and Mars, potentially providing more insight into the origins of the solar system as a whole,  wrote Inverse.  

However, lead study author Jessica Barnes, a Ph.D. candidate at the Open University, told The Verge that there are still more questions that need to be answered. The study used data collected from lunar rocks that were brought back by the Apollo Missions although only 2 percent of them were analyzed for water.

 “Imagine you were an alien and you went to Earth and you only went from Glasgow to Edinburgh and back again,” she said. “You wouldn’t understand a whole lot about the Earth. You’d be missing the pyramids, you’d be missing the Grand Canyon. Although we’ve done a lot with the material that we have, there’s still much of the Moon we haven’t explored yet.”

The study was published in the journal Nature Communications.