After Apollo, the space scientists examining the returned moon rocks thought that they contained no trace of water. They concluded that the moon must be dryer than old bones (literally).
But this conclusion has long been questioned. It could be that any evidence of water those early researchers did see was dismissed because of fears of contamination from Earth’s atmosphere; none of the boxes in which the lunar samples were returned kept their vacuum.
The picture began to change significantly in 1994 when a joint NASA–military satellite called Clementine was thought to have detected traces of water frozen in the shadows of a lunar polar crater. This raised great hopes, though doubt was cast on the result later. In 1999 another NASA probe called Lunar Prospector was deliberately crashed into a south pole crater, in the hope of raising a plume of dust laced with sparkling water—but again the results were inconclusive.
Today, however, thanks to discoveries in 2009 from India’s Chandrayaan-1 spacecraft, and NASA’s Lunar Reconnaissance Orbiter and Lunar Crater Observation and Sensing Satellite, we believe there might be three sources of water on the moon. The shadows of polar craters, forever dark, could act as cold traps. There could be trace amounts of water in volcanic glasses. And finally there might be water scattered over the moon’s surface—just traces, the slightest dew in the regolith (the lunar soil), delivered by comet impacts after the moon’s formation.
Water in space would be hugely valuable, far more so than gold, given the cost of hauling water up from Earth. On the moon, water would support life, and using electrolysis (passing an electric current through it) water can be broken down into hydrogen and oxygen to make rocket fuel. The moon could become a filling station outside Earth’s deep gravity field that could be used to support a general expansion into the solar system, just as was dreamed of before Apollo.
Another key resource to be found on the moon is helium-3, the isotope of this light element that is most useful in fusion reactors. Unfortunately, like the water, the helium-3 is implanted thinly in the regolith, having been deposited there by the solar wind over aeons. (In the Avatar universe RDA does in fact maintain a lunar helium extraction facility.)
The moon, however, is only the beginning of our search for water and other resources beyond the Earth. And it may not even be the first place we’ll look. In April 2010 the Obama administration set out a startling and terrifically exciting new vision for the future of American manned spaceflight. The next small step an American astronaut makes on another world might not be the moon, or even Mars, that traditional destination, but an asteroid.
On the very first day of the nineteenth century, a new world was discovered. Smaller than any planet, it was an asteroid, now called Ceres, the first discovered, and the largest of them all, as it turned out, circling in the great waste between Mars and Jupiter. Other asteroids soon followed: more than four hundred lumps of rock and ice were discovered by the end of the nineteenth century. The asteroids are thought to be relics of the solar system’s formation, fossil remnants never gathered up into planets.
Then in 1898 a new type of asteroid was discovered. Christened Eros, this flying mountain can wander within the orbit of Mars, and even comes distressingly close to Earth. Today we know of many asteroids whose paths take them near our planet. Known as near-Earth objects (NEOs), most of them are only a few kilometres across or less. There may be as many as two thousand NEOs more than a kilometre across, and maybe two hundred thousand more than a hundred metres across. About a fifth of them will eventually hit Earth—“eventually,” in this context, meaning over billions of years. The famous impact sixty-five million years ago which appears to have caused the extinction of the dinosaurs was in fact caused by a NEO. Today we are tracking NEOs with programmes run by NASA and other agencies; one day we may be able to push away any threats.
However it is not the threat of the NEOs that interests us here, but their promise.
Obama’s new vision would send astronauts to a NEO. We know we can reach them; already asteroid Eros has been orbited by an unmanned spacecraft. And surprisingly, perhaps, some of the NEOs come so close to Earth that it would take less fuel to reach a NEO and return than it takes to get to the surface of the moon and back. The catch is that it takes much longer to get to a NEO than the moon. In a way that’s a benefit; an asteroid mission could be a rehearsal for the even longer missions to Mars to come. The operation would be tricky; an asteroid’s gravity is so low that “landing” would be more like docking with an immense natural space station. Once there the astronauts could trial technologies for pushing rogue NEOs away from an Earth impact.
And NEOs themselves could prove to be very valuable prizes indeed.
Some NEOs are flying mountains of natural steel and precious metals, such as gold and platinum. The prospect of reaching what is known as a C-type asteroid, full of organic compounds, is even more exciting, because the C-types contain water. Not only that, with suitable engineering, you can also extract from the asteroid dirt carbon dioxide, nitrogen, sulphur, ammonia, phosphates—all the requirements of a life-support system, or a rocket fuel factory. You can also use the asteroid dirt to make glass, fibreglass, ceramics, concrete.
A logical early project using asteroid resources would be the construction of a solar power plant in Earth orbit. The high-technology components of the plant, such as guidance, control, communications, power conversion and microwave transmission systems, would be assembled on Earth. The massive low-tech components, cables, girders, bolts, fixtures, station-keeping propellants and solar cells, would all be manufactured in space from asteroid materials. The plant would produce energy, safe, clean, pollution-free, to be sold back to Earth.
This isn’t fantasy. Schemes to exploit the NEOs are approaching the feasibility of business plans; hard-headed entrepreneurs are considering ways to reach these mines in the sky. And once we get there, resources and power are going to start flowing down from the sky to the Earth.
Perhaps this is how we will save the world from an Avatar-style ecocide. In Part One we looked at the bottleneck we face on Earth: a bottleneck caused by diminishing resources, and the diminishing capacity of Earth’s environment to withstand the disturbances we are causing to extract those resources. If population continues to grow—and, just as significantly, if we continue to aspire to a better standard of living for all of us—we’re going to need economic growth, which means a growth in the usage of resources. And maybe space resources, extracted without further impact to the Earth, could be a way through the bottleneck.
Maybe it doesn’t have to be the way Jake Sully bleakly summarised it to Eywa. Maybe there is a way for us to keep the Earth green, without giving up our civilisation and all the benefits it brings: by using the resources of space.
What if we keep expanding? Beyond the moon, beyond the NEOs, what riches lie waiting further out in the solar system?
Let’s follow the water. We need a lot of ingredients to live, but water is by far the most fundamental.
It turns out that the whole of the inner solar system out to Mars—planets, near-Earth asteroids and all—could supply only enough water for maybe fifty billion people. That’s a lot, but only six or seven times the number of people alive today—or, put another way, seven billion people consuming seven times as much resource each.
Happily there is a lot more water in the outer solar system. There are a vast number of asteroids in the main belt, orbiting between Mars and Jupiter, perhaps ten billion larger than a hundred metres in diameter, and a hundred billion between ten and a hundred metres across. They are rich in water, metals, phosphates, carbon, nitrogen, sulphur. The main-belt asteroids could contribute about half the water available on Earth, vastly expanding mankind’s opportunities for growth.
The main belt may not be the most interesting territory to prospect asteroids, however. The asteroids tend to occur in groups, shepherded by orbital resonances with the planets. Some of the most significant groups are known as the Trojan asteroids. These are not in the main belt but in Jupiter’s orbit, at the so-called Lagrange points, points of gravitational stability. As a result the Trojans are comparatively close together; by comparison, the main belt asteroids are spread over an orbit wider than that of Mars.
And the Trojan asteroids are rich. It is believed that the asteroid mass available in the Trojans is several times greater than that in the main belt itself. Not only that, they seem to be even more volatile-rich than the C-type asteroids and comet nuclei. Some analysts think the Trojans might prove to be the richest single resource pool in the solar system.
Beyond the asteroids, ambitious prospectors could settle on the moons of the outer planets, some of which are little more than giant balls of water-ice. A single ice moon has around forty times as much water as all Earth’s oceans. The last planet to be discovered, Pluto (though it’s no longer regarded as a planet at all) is believed to be but one of a whole cloud of similar objects, icy worldlets and massive comet nuclei, circling silently in the dark. The cloud may extend some hundred thousand times as far as Earth is from the sun—that’s halfway to Alpha Centauri. The cloud may have a mass as much as ten times all the planets in the solar system combined…
What a vision this is! Water is only one of the resources waiting for us out there. Imagine an interplanetary civilisation, the solar system transformed by baby RDAs into a savage competitive arena of giant mining vessels, plying the space lanes and dismantling moons—a sky full of Pandoras.
But you might hope that amid all this industry we will find it in us to preserve the natural wonders of the solar system. Including our very own Pandora.