The Earth is a very, very wet place. The surface is largely covered with liquid water, but scientists have long debated exactly how so much of it ended up here. If the most widely-held Earth formation theories are correct, the early Earth would have had a hard time hanging on to water during its earliest years, so researchers have been focused on other theories of how it may have arrived. Once such theory just got some solid supporting evidence thanks to a high-speed cannon and some rocks.

Scientists have suggested that if our planet was mostly dry in the time period immediately following its formation, water may have crashed down from the sky in icy asteroids. However, whether or not such a thing was even possible has long been debated. Some in the scientific community tossed the idea aside, believing that the impact of any water-carrying asteroid would have vaporized the water and made it nearly impossible for large bodies of liquid water to form.

As Science News reports, a small team of scientists from Johns Hopkins University and Brown University decided to test the idea that an asteroid could effectively deliver water without destroy its life-giving payload in the process. To do it, the researchers fired rocky pellets made of the mineral antigorite — thought to be an analog for the kinds of objects that may have brought water to our planet — at a hard, dry surface made of pumice.

The tests, which they carried out at NASA’s Ames Vertical Gun Range, revealed that while the majority of the water in the rock was indeed vaporized on impact, some of it became encased in the glass created on impact. Using their data, the researchers suggest that as much as 30 percent of the water in an asteroid could have successfully remained on the Earth’s surface following a collision.

The work, which was published in Science Advances, is far from a conclusive answer for the question of how Earth got all of its water, and there are still many questions left to be answered. For example, the scientists still need to explain how the captured water within the post-collision rock leak out to form larger bodies. Nevertheless, it’s an important finding that could help inform future research, and perhaps one day answer the question with greater certainty.

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