Projectile cannon tests show how water can survive asteroid impacts

April 26 (UPI) — Scientists have credited comets and asteroids with delivering water and other elements necessary for life to Earth shortly after the planet was formed. But impact models suggest water should be entirely boiled away by the heat generated by such a collision.

Brown University researchers used a high-powered projectile cannon to investigate the contradiction. The results of their experiments, detailed this week in the journal Science Advances, suggest surprising amounts of water can survive asteroid impacts.

“The origin and transportation of water and volatiles is one of the big questions in planetary science,” Terik Daly, now a postdoctoral researcher at Johns Hopkins University, said in a news release. “These experiments reveal a mechanism by which asteroids could deliver water to moons, planets and other asteroids. It’s a process that started while the solar system was forming and continues to operate today.”

Originally, scientists thought icy comets supplied most of the water found on Earth, but isotopic analysis suggests Earth’s early water supply was most similar to water found trapped in carbonaceous asteroids.

How exactly water would survive a rock-on-rock collision, however, has remained a mystery. Computer models suggest all water would be completely vaporized during such a collision.

“But nature has a tendency to be more interesting than our models, which is why we need to do experiments,” said Pete Schultz, professor of planetary science at Brown.

Schultz, Daly and their colleagues built miniature asteroid models based on the composition of carbonaceous chondrites, the remains of water-rich asteroid fragments that struck Earth long ago. The research team loaded the mini asteroids into the Vertical Gun Range at the NASA Ames Research Center and shot them into a compacted wall of pumice powder at speeds of approximately 11,000 miles per hour.

Scientists replicated impacts featuring speeds and angles common throughout the solar system. They found as much as 30 percent of the original water content remained trapped in the fragments that survived the collisions.

Though almost all of the water is vaporized, some of that vapor gets trapped in a plume of impact material and reincorporated into debris as melted rocks cool into solid fragments.

“The impact melt and breccias are forming inside that plume,” Schultz said. “What we’re suggesting is that the water vapor gets ingested into the melts and breccias as they form. So even though the impactor loses its water, some of it is recaptured as the melt rapidly quenches.”

The research could not only help explain water on early Earth, but also more recent signs of water on the moon and the planetary bodies.

“The point is that this gives us a mechanism for how water can stick around after these asteroid impacts,” Schultz said. “And it shows why experiments are so important because this is something that models have missed.”

Earlier this year, researchers in Russia blasted miniature asteroid models with a high-powered laser to better understand the kinds of forces needed to destroy a space rock headed for planet Earth.

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