Scientists have speculated for years where Earth's water comes from. A Glasgow-based group including two scientists from the University of Hawaiʻi at Mānoa made the first positive identification of an asteroid bringing water to Earth.
The team studied samples from Itokawa — an asteroid that orbited close to the Sun and was collected by the Japanese space probe Hayabusa in 2010. They analyzed each space dust at an atomic level and found water molecules inside the grains.
They estimate 50% of Earth’s water comes from asteroids hitting the planet.
Asteroids and comets collect water in a process known as space weathering.
When asteroids fly by the Sun, they fly through solar winds that are almost entirely composed of hydrogen. The solar winds break down the chemical composition of the rocks and bond the hydrogen with oxygen. The water gets trapped in minerals in the asteroids and crash land into Earth.
Professor Hope Ishii from UH Mānoa explains, "There’s basically three ways to get water into a planet. There’s water that would have been included when the bodies first got together and formed a big mass. But there isn’t enough from that, so you can also add water by smacking water-bearing objects into the Earth, and that would be asteroids and comets that would provide additional water."
"Then this mechanism where the solar wind protons, hydrogen ions, actually reacting with the oxygen in rocks would be the third source of water," Ishii describes.
Earth was then able to retain the water thanks to its atmosphere and perfect distance away from the Sun. The planet is nicknamed the "Goldilocks Planet" — not too hot and not too cold for water to maintain its liquid form.
The findings made by Ishii and her research team could help space explorers develop a method to create water on other planets.
