April 26, 2018
Scientists Devise Cannon Experiment To See How Asteroids Could Have Brought Water To Earth

The theory that Earth's water may have come from asteroids is not a new one. In fact, past research has shown that the water on our planet has a similar composition of isotopes as water found in carbonaceous asteroids — ancient, water-rich space rocks that frequently pounded Earth during the planet's early years.

What did remain a mystery until now was how these asteroids were able to deliver water to our previously arid planet in its incipient stages of development.

A pair of scientists from Brown University believe they may have found the answer and published a study in the journal Science Advances to tell us how it all could have gotten down (yes, that was an attempt at a pun).

The team concocted an experiment that used projectile cannon blasts to simulate the force of high-velocity asteroid impacts and test how much water content — if any — could be transferred through such collisions.

For the purpose of this exercise, the researchers used marble-sized projectiles similar in composition to carbonaceous chondrites (meteorites recovered from carbonaceous asteroids) and fired them at volcanic rocks at speeds of 11,200 mph, or around 18,000 km/h, reports Space.com.

The experiment, conducted with NASA's Vertical Gun Range at the Ames Research Center in California, uncovered that an asteroid could deliver up to 30 percent of its water content in this type of collision that later becomes trapped in debris following the impact.

Although impact models constructed in the past showed that asteroids usually devolatilize during collisions at many of the speeds typically found in our solar system, this new test revealed that water doesn't always boil off in the heat of the impact. In fact, it can actually stick around and get caught in rocks and debris from the asteroid impact.

"Most of that water was trapped in impact melt, rock that's melted by the heat of the impact and then re-solidifies as it cools, and in impact breccias, rocks made of a mish-mash of impact debris welded together by the heat of the impact," according to a news release by Brown University.

Study co-author Peter Schultz, a professor at the university's Department of Earth, Environmental and Planetary Sciences, chimed in to explain the process.
"What we're suggesting is that the water vapor gets ingested into the melts and breccias as they form."
This means that, although asteroids lose their water content in high-speed impacts with other celestial bodies, some of this water is recaptured as debris coalesces and melted rocks cool off.

According to study co-author Terik Daly, who has since become a postdoctoral researcher at Johns Hopkins University in Maryland, the origin and delivery of water remains one of the biggest mysteries in planetary science.

"These experiments reveal a mechanism by which asteroids could deliver water to moons, planets and other asteroids," Daly said in the news release.