The most important resource that will be mined in space is water.
Water is critical for all life-support functions in space: sustenance, hygiene, and food production. Water can serve as an effective shield from the dangerous radiation present in space. Water is also the single most important feedstock for in-space refineries, which will produce rocket propellants for sale to transportation providers.
Making propellants available beyond Earth’s gravitational influence will lead to the creation of the first in-space superhighway – a series of fuel depots placed in strategic locations throughout the solar system.

Imagine the growth potential of the energy, mining, and refining industries once they are freed from the constraints of an economy that is limited only to Earth. The in-space transportation and logistics firms who will consume these products are already well established and are headed by titans of industry: Jeff Bezos (Blue Origin), Elon Musk (SpaceX), Richard Branson (Virgin Galactic), and Tory Bruno (United Launch Alliance). The door is now open to in-space mining firms like Planetary Resources (backed by industrial giant Bechtel and the Government of Luxembourg) to capture this increasingly important market by providing water and water-based propellants to the space transportation industry.