Where did Earth’s water come from? - The National

The findings, published in the Nature Astronomy journal, showed a significant amount of water was produced below the surface of dust-sized grains from Itokawa by space weathering – which occurs when charged particles from the Sun, known as solar wind, change the chemical composition of the grains to produce water molecules.

“By showing for the first time that water is produced in situ on the surface of an asteroid, our study builds on the accumulating body of evidence that the interaction of the solar wind with oxygen-rich dust grains does indeed produce water.".

The team used a technique known as "atom probe tomography" to measure the atomic structure of the grains one atom at a time and detect individual water molecules.

It is expensive to launch water into space and scientists are hopeful that future astronauts will be able to produce water supplies on site when exploring the Moon or other planets one day

“We think it’s reasonable to assume that the same space-weathering process which created the water on Itokawa will have occurred to one degree or another on many airless worlds like the Moon or the asteroid Vesta