Humans settle around water, especially in the desert. Indeed, our earliest civilizations developed around desert water bodies like the Nile, Tigris, and Euphrates. With NASA’s recent discovery of evidence of liquid water on the desert planet Mars, a new extraterrestrial civilization could arise on Mars, and it will almost certainly be near a Martian lake, river, or well. Let’s assume for the sake of argument that the water is potable, or at least can be treated and become usable for human purposes. In that case, who has the right to this water, and how should it be allocated? Perhaps the answer lies in a 19th-century U.S. water law policy designed to encourage the innovations and entrepreneurialism necessary to explore and colonize the American West.
In the 19th century, the United States acquired enormous tracts of undeveloped desert land. Under the banner of Manifest Destiny, American leaders created policies to promote settlements in the arid region. Key among those policies was an innovative approach to water rights—the law of prior appropriation, under which the first person to capture a quantity of water and put it to beneficial use had superior rights to that quantity of water than all other subsequent users. This regime provided an incentive for smart, industrious people to run as fast as they can into the desert, an attitude that was essential to achieving the aims of Manifest Destiny. A water user’s right dated back to the day the user first attempted to divert water for beneficial use, so long as the user was diligent from that day until finally putting the water to beneficial use. For example, if a settler in Arizona began digging a diversion ditch on the Gila River in June 1875 and worked on that diversion until finally irrigating crops in December 1875, he would have a superior water right to another person who diverted in July 1875 and began irrigation in November. Prior appropriation was an orderly way to encourage industry to subdue a harsh desert.
This might be just the answer to the question of how we create incentives for people to undertake the incredible expense and risks required to settle the red planet. If the international community knew that the first nation (or company) to capture a quantity of Martian water and put it to beneficial use had superior rights to all subsequent users, it could spur the types of innovation and entrepreneurialism needed for interplanetary exploration and colonization. Human curiosity and the impulse to explore will likely motivate some efforts to reach Mars. But those could range from the credible but politically complicated NASA missions, to less realistic endeavors, like those of Mars One. But a sustainable investment in the development of Mars will likely require stronger incentives. Under a prior appropriation water rights regime, those who invest in the first successful venture to Mars and actually use Martian water would have superior rights to any subsequent users. The first mission to Mars would have to include drilling a well or installing a pump or diversion ditch on a stream. But those first water users would have to remain diligent in developing the resource until it was put to beneficial use, or risk losing their water priority. This would encourage long-term planning for multiple missions to Mars.