Latest discoverings show that one of the most common constituents of the asteroids is water. That is amazing, even more because it can be used in-site as a resource or as fuel

In addition to the metals, the elements to create water are present in asteroids and there are indications that asteroids contain water or ice in their interiors, and there’s even evidence that water may have flowed on the surface of at least one asteroid. Observations of Vesta from the Dawn mission show gullies that may have been carved by water. The theory is that when a smaller asteroid or comet slams into a bigger asteroid, the small asteroid or comet could release a layer of ice in the bigger asteroid. The force of the impact briefly turned the ice into water, which flowed across the surface, creating the gullies.

https://www.universetoday.com/37425/what-are-asteroids-made-of/