Water is everywhere on our planet. If it does not crash against the shore, knock it on the roof or drip from the tap or gather right where you just stepped. But how did all the water come here?
It's a question that has kept planetary scientists busy for years. Have planets like Earth, Mars, Venus and Mercury formed dry from the dust and heat of the Inner Solar System to be later soaked in water from ice-laden comets? Or did drier asteroids and asteroid collisions bring the wet stuff?
"Water is critical to life as we know it, and it is also essential to the evolution of planets." Water changes the way rocks behave, so the timing of when water flows on the water Earth arrives, its geological evolution, "says Terik Daly, a planetary geologist. "We have known for some time that asteroids and comets carry water, so water probably came to Earth, but the details of this process were somehow a black box."
Computer models are beginning to give us answers to these questions. But the models only go so far. To truly understand how this water delivery system works, you need to watch it. But meteor attacks are notoriously unpredictable, so the researchers decided to create their own using an oversized cannon at NASA's Ames Research Center. The research, led by Daly, was just published this week Science Advances .
"Impact models tell us that at many of the impact speeds common in the solar system, impact models should completely degas water they contain boiling in the heat of the crash," said co-author and geoscientist Pete Schultz in a statement. "But nature tends to be more interesting than our models, so we have to do experiments."
NASA built the Ames Vertical Gun Range in the 1
To simulate a water-rich asteroid that smashed into the surface of another asteroid, the team fired no more than a bb pellet into a thin bed of pumice powder. Pumice is a glass that forms when lava cools very quickly and the powdery substance resembles the surface of an asteroid. They heated the pumice for one and a half hours at temperatures above 1500 degrees Celsius to heat all the water in them.
Delivering the water to this dry powder was serpentine pellets, a mineral that is already abundantly bound on Earth in its molecular structure – it is also found in meteorites called carbonaceous chondrites.
The vertical cannon is loaded, the tray of ultra-dried pumice stones underneath and then … bang! It's all in a second.
The serpentine pellet strikes the pumice surface at over 11,000 miles per hour, tearing through the thin mylar shell it holds. Parts of the rock diverge, and the impact is enough to melt pieces of rock and pumice, creating a glass. And this glass held water.
Instead of just cooking on impact, some water got stuck. Part of it remained trapped in pieces of the projectile, which were broken apart as it hit the pumice surface, but a lot of it mingled with the molten glass. If that had been a true asteroid impact, enough water would still be delivered to the target.
The results only show how an asteroid that struck another asteroid looks like no ansteroid on a larger object like the Earth or the Moon. To simulate these effects would require much more powerful equipment, but that tells us a lot about how this process could work on larger bodies.
"The experiments we do in the lab are small, and planets and asteroids are very large, but we take what we see in the lab, and we try to understand that very well, and we take what we do Know how high-impact effects work and use these principles to guide the results of interpreting these experiments, "says Daly.
For example, geoscientists know that the impact speeds on the moon are much higher than in the laboratory. And they also know that impacts that happen at higher speeds produce more molten material. If the impact melt on the moon intercepts water in the same way as the melt in the experiments, then the experimental mechanisms should persist on even larger scales.
Ideally, Daly and his colleagues would put asteroids into the solar system with watermarks on their surface to see if the percentage of water trapped there matches their experimental results. It could help researchers understand some of the fundamental dynamics of the solar system today, as well as providing insights into the origins of our solar system and our planet.
"The whole question of the origin of the water and where it comes from and how it is It is very important to understand the origin and evolution of the earth, and on the largest scale, how it became the place where we find ourselves today, "says Daly.