The interior planets of the Solar System are supposed to be quite dry. That’s simply how they formed. So how come the surface of our world is dominated by water? Planetary scientists thought for a long time that comets delivered the precious liquid, but over the last few years, evidence has shown that these icy bodies were not the carriers. Instead, asteroids are the most likely candidates
Now, researchers have used a powerful cannon to show how water-rich asteroids can deliver water to planetary bodies. As reported in Science Advances, the space rocks can deliver a surprising amount of H2O.
"The origin and transportation of water and volatiles is one of the big questions in planetary science," lead author Dr Terik Daly, from Johns Hopkins University, said in a statement. "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."
The question that researchers had was an obvious one. Can water and other molecules survive an asteroid impact? To find an answer they used the Vertical Gun Range at the NASA Ames Research Center. They shot marble-size projectiles, similar in composition to the original water-rich asteroids, to a target at the impressive speed of 5 kilometers (3.1 miles) per second (more than 17,700 kilometers or 11,000 miles per hour).
The team used an impact speed that's common in the Solar System and hit the targets at angles within the reasonable range for most impacts. They discovered that 30 percent of the original water survived the impact and most of that was then trapped in the impact melt, the material that melts due to impact and then resolidifies into rocks, and impact breccia, the debris welded together in the aftermath.
"The impact melt and breccias are forming inside that plume," Professor Pete Schultz from Brown University explained. "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."
Water-rich impactors like carbonaceous asteroids are believed to have been some of the earliest objects in the Solar System. Something similar to what has been seen in this study could explain the delivery of water to Earth. And that’s not all. Asteroid-delivered water can also explain ice deposits in some craters on the Moon and Mercury.