Unlocking the solar system with water from asteroids

January 30, 2014

(Journal Nature) Ceres, a dwarf planet in the asteroid belt, is spewing water vapor out into space. In fact, Ceres might hold more water than Earth does.

Over the next 2 years, NASA's Dawn mission, which has already visited big asteroids such as Vesta, will arrive at Ceres to map the dwarf planet's surface. And the ESA's (European Space Agency) Rosetta mission, which just emerged from hibernation, will chase a comet as it approaches the sun. While the two missions have different objectives, both have the potential to tell us more about where all the water in our solar system came from.

The discovery of water vapor on Ceres means that planetary scientists have another destination for possible astrobiology-based missions to seek out new life. "It clearly puts Ceres in the same category as Europa and Enceladus as candidates for life," Raymond say.

Planetary Resources and Deep Space Industries are two companies that want to mine the asteroids. However, they are looking at smaller asteroids in orbits closer to the Earth.

Planetary Resources describes how water from asteroids will unlock the solar system

There are over 1,500 asteroids that are as easy to get to as the surface of the Moon. They are also in Earth-like orbits with small gravity fields, making them easier to approach and depart.

Water from Asteroids

Water from asteroids is a key resource in space. Water can be converted to rocket propellant, or supply the needs of humans living off Earth, and can completely change the way we explore space with rockets. A single water-rich 500-meter-wide asteroid contains 80 times more water than the largest supertanker could carry and could provide, if the water were converted to rocket propellant, more than 200 times the rocket fuel required to launch all the rockets ever launched in human history.

Rare Metals from Asteroids

Once we are able to access, process, and utilize asteroid water resources, mining metals becomes more feasible. Some near-Earth asteroids contain platinum group metals in much higher concentrations than the richest Earth mines. In space, a single platinum-rich 500 meter wide asteroid contains about 174 times the yearly world output of platinum, and 1.5 times the known world-reserves of platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum). This amount is enough to fill a basketball court to four times the height of the rim. By contrast, all of the platinum group metals mined to date in history would not reach waist-high on that same basketball court.

Other Asteroid Resources

Asteroids also contain more common metallic elements such as iron, nickel, and cobalt, sometimes in incredible quantities. In addition to water, other volatiles, such as nitrogen, CO, CO2, and methane, exist in quantities sufficient to warrant extraction and utilization.

Water: Unlocking the Solar System

Water from asteroids can be both converted to and used directly as propellant, then shipped and stored at strategic locations set up as fuel depots. This fuel – supplied and sold to NASA or other in-space customers – will dramatically accelerate the pace of human spaceflight.

Asteroid water can sharply reduce the cost of human spaceflight missions because the mass of most deep space missions is primarily comprised of propellant. For example, it is more energetically efficient to carry a liter of water or propellant from a near-Earth asteroid to an Earth orbit destination than it would be to carry that same liter of water from the Earth’s surface.

In Earth orbit, water from asteroids can also be converted and used to refuel satellites, increase the payload capacity of rockets by refueling their upper stages, reboost space stations, supply propellant needed to boost satellites from Low Earth Orbit to Geostationary Orbit, provide radiation shielding for spaceships, and provide fuel to space tugs that could clean up space debris.

Water Value

A 500 meter diameter water rich asteroid has $50B (billion) worth of water deliverable to a deep space fuel depot, even if one makes the conservative assumptions that: 1) only 1% of the water is extracted; 2) half of each load of water is consumed en route for propulsion; and 3) the success of commercial spaceflight causes the cost of Earth-originating launches to drop by a factor of 100. Of course, less conservative assumptions would raise the value of the asteroid to many trillions, or even tens of trillions, of dollars.

The economics of an asteroid mining operation can also be enhanced by the use of in-situ propellant. Mining spacecraft can travel across interplanetary space using water reclaimed from the very asteroid it is mining, leading to a high “mass payback ratio” where a single ton of mining equipment can be used to obtain hundreds of tons of mined resources.

Moving from Water to Metals

Once water mining operations are successful, the economics of space travel will have changed such that the reclamation of other asteroid resources becomes more feasible. In a very real sense, mining water ultimately enables the mining of metals.

Platinum group metals are extremely rare on Earth and these metals, and others like them, have special chemical properties that make them incredibly valuable for important industrial processes in the 21st century economy. An increase in abundance of rare metal resources could also enable new, unforeseen applications that exploit the properties of rare metals beyond the current state of practice.

Using Asteroid Metals in Space

In addition to being brought back to Earth, metals from asteroids can also be used directly in space. Metals like iron or aluminum can be moved to collection points in space for purposes such as space construction materials, spacecraft shielding, and raw material for industrial processes at, for example, a future NASA deep space L2 space station.