Scientists Used a Super Powerful Cannon to Show How Asteroids Can Carry Water Between Worlds

A French scientist holds a chondrite meteorite, the sort of rock the new study mimicked. Benoit Tessier/Reuters

The Earth's nickname, "the Blue Marble," comes from being covered with water—but where did that water come from? It's one of science's biggest mysteries, and plenty of ink has been spilled trying to design scenarios that make sense.

But there's another approach: dreaming up experiments that could demonstrate how those scenarios might have played out. A new attempt to mimic water's arrival on Earth made use of an exotic tool—an incredibly powerful cannon that parodies an asteroid impacting Earth. The results are published in the journal Science Advances.

"Nature has a tendency to be more interesting than our models, which is why we need to do experiments," co-author Peter Schultz, a planetary scientist at Brown University in Rhode Island, said in a press release.

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Models had suggested that water may have arrived on Earth through impacts by a group of objects called carbonaceous chondrites—meteorites that break off an asteroid full of water and fall to Earth. However, scientists worried that all that water could have evaporated away during the incredibly hot conditions of impact.

So the team turned to NASA's Vertical Gun Range in California, which was designed to produce small replicas of the sort of high-power collisions that are common in space. The device is powerful enough to shoot a marble at speeds of more than 11,000 miles per hour, which is still only about half the speed of the slowest meteorite impacts.

The scientists made small marbles with the same recipe as the wet carbonaceous chondrites, then used the high-power cannon to shoot it into a very dry rocky surface. The result was a mess of melted and rehardened rock.

By measuring the water content of that rock and comparing it to what they started with, the team confirmed that about two-thirds of the water was lost during impact but that the rest ended up locked inside the rock. Scientists believe that early in Earth's life, it would have been pummeled with one after another of these impacts—and the new evidence suggests that those impacts could add up to the watery world we love so much.