Forget Mars. Here's Where We Should Build Our First Off-World Colonies

The collective space vision of all the worlds countries at the moment seems to be Mars, Mars, Mars. The U.S. has two operational rovers on the planet; a NASA probe called MAVEN and an Indian Mars orbiter will both arrive in Mars orbit later this month; and European, Chinese and additional NASA missions are in the works. Meanwhile Mars One is in the process of selecting candidates for the first-ever Martian colony, and NASAs heavy launch vehicle is being developed specifically to launch human missions into deep space, with Mars as one of the prime potential destinations.

But is the Red Planet really the best target for a human colony, or should we look somewhere else? Should we pick a world closer to Earth, namely the moon? Or a world with a surface gravity close to Earths, namely Venus?

To explore this issue, lets be clear about why wed want an off-world colony in the first place. Its not because it would be cool to have people on multiple worlds (although it would). Its not because Earth is becoming overpopulated with humans (although it is). Its because off-world colonies would improve the chances of human civilization surviving in the event of a planetary disaster on Earth. Examining things from this perspective, lets consider what an off-world colony would need, and see how those requirements mesh with different locations.

First, lets take a look at what the mooted Mars settlement schemes are offering. The Red Planet has an atmosphere containing carbon dioxide, which can be converted into fuel while also supporting plants that can make food and oxygen. These features could allow Martian colonists to be self-sufficient. They could live in pressurized habitats underground most of the time, to protect against space radiation, and grow food within pressurized domes at the planets surface.

Over decades, continued expansion in that vein could achieve something called paraterraforming. This means creation of an Earthlike environment on the Mars surface that could include not only farms but also parks, forests, and lakes, all enclosed to maintain adequate air pressure. (The natural Martian atmosphere exerts a pressure of only 7 millibars at the planets surface equivalent to being at an altitude of 21 miles on Earth!)

Mars colony illustration. Credit: NASA

Furthermore, in addition to adequate pressure, wed need a specific mixture of gases: enough oxygen to support human life, plus nitrogen to dilute the oxygen to avoid fires and to allow microbes to support plant life. While the small spacecraft in which astronauts fly today carry food and oxygen as consumables and use a simply chemical method to remove carbon dioxide from the air, this type of life-support system will not swing on a colony. As on Earth, air, water, and food will have to come through carbon, nitrogen, and water cycles.

While it would cost a ton of money to build, paraterraforming sections of Mars with a sample of Earths biosphere inside pressure domes, caves, and underground caverns is something that we could achieve within years of arrival of the first equipment. Moving beyond paraterraforming is a more ambitious goal that could require centuries, and thats full-scale terraforming. This means engineering the planet enough to support humans and other Earth life without domes and other enclosed structures.

Terraforming Mars would require that the atmosphere be thickened and enriched with nitrogen and oxygen while the average temperature of the planet must be increased substantially. To get started, terraformers might seed the world with certain microorganisms to increase the amount of methane in the Martian air, because methane is a much stronger greenhouse gas than carbon dioxide. They also would seed dark plants and algae across the surface, thereby darkening the planet so that it absorbs more sunlight.

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Forget Mars. Here's Where We Should Build Our First Off-World Colonies