Slow-motion impact
GIF: Terik Daly (Brown University)

You may have heard the theory that asteroids are responsible for Earth’s water. You may also have thought, hah, there’s no way that asteroids could have brought all that water to Earth. But fake asteroid impacts are now demonstrating that, yeah, maybe they did.

Scientists from Brown University have found that the melted rocks from asteroids “trap surprisingly large quantities of water.” And that’s important not just to our own planet’s story, but to others’, too.

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“If impacts successfully trap water in growing planets in other planetary systems—and we have every reason to believe that they should—then many planets should have water on or in them,” study author Terik Daly from Brown told Gizmodo. “If that water is a liquid (rather than water vapor or ice), then, bingo, you’ve got one of the three key ingredients for life as we know it.”

The researchers’ experiment used the NASA Ames Vertical Gun Range, which is, as its name implies, a vertical gun. It’s been around since the 1960s to help study high-speed impacts as part of Project Apollo. For the experiment, which took place in a vacuum, the researchers loaded up the 2.5-meter gun with mock asteroids made from the mineral antigorite, which they shot five times faster than a speeding bullet, 11,200 miles per hour, at a 45 degree angle downward at waterless pumice volcanic rock, which represented our mock Earth.

Glass left over from the impact
Photo: Terik Daly

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The outcome was a mess—leftover meteorite pieces, breccias (a rock consisting of lots of connected smaller chunks), and glasses generated from the impact’s high heat. All three contained water left over from the asteroid pieces, according to the study published today in Science Advances. Water vapor escaping from the meteorite could have been trapped by the forming breccias and glasses.

One researcher not involved with the study, Kathrin Altwegg from the Universität Bern in Switzerland, told Gizmodo this was a “beautiful experiment and result.” Most importantly, it demonstrates how crucial real, tangible experiments are, as opposed to just debating models.

Some scientists aren’t happy with the idea of asteroids delivering water to Earth, she explained, based on their models. They claim “that upon impact all water and volatiles are lost,” she said. But this experiment “makes it more likely that indeed asteroids could be the source of terrestrial water.

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The vertical gun.
Photo: NASA

This is an ongoing debate, and a single paper won’t answer where the Earth’s water came from alone. Additionally, this is a small-scale experiment, not a real meteor impact, so it’s not a perfect test of the theory.

But marbles shot from an enormous gun seem to suggest that, yes, perhaps asteroids really could have delivered some of the watery goods that made Earthly life possible.

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[Science Advances]