As you read this, you’re one of nearly 7 billion human beings on this planet. And that number is likely to increase massively. In fact, if the population of Earth continues to increase at its current rate, there will be over 10 billion people in the world by the year 2050. As we start to run out of space on Earth, there’s one particularly audacious possible solution. What if we could shape another planet into a second Earth?

PHOTOS: A ‘Lifeless’ Red Mars as Seen by Curiosity

Terraforming is the hypothetical process through which we could engineer the surface of an entire planet to make it habitable for our own planet’s life to thrive. We’ve certainly proven that we can influence and alter the environment of a whole planet, even though in the case of Earth the results weren’t exactly beneficial. Or desirable. The difficult part is, given a blank canvas, we aren’t entirely sure how to even begin.

In science fiction, the concept of terraforming is quite widespread; it features prominently in cult titles like Firefly, Cowboy Bebop, and Star Trek. Don’t let that make you think the idea is pure fiction though.

Many scientists and engineers have given serious thought to the puzzle of how to terraform a planet, and NASA has even hosted meetings and debates on the topic. As you might expect, the whole operation is far from straightforward.

Terraforming literally means “Earth shaping”, and in order to shape a barren, hostile planet into a new Earth, we’d need a few key ingredients. Specifically, it would need to have an atmosphere with the correct pressure, oxygen and carbon dioxide in that atmosphere for respiration and photosynthesis to take place. It would also need the right range of temperatures that would allow for, the pièce de résistance, liquid water.

On a small scale, these things are fairly easy to accomplish. On the surface of an entire planet? Not so much.

ANALYSIS: The Ethics of Planetary Exploration and Colonization

Earth life is surprisingly resilient, surviving habitats from the crushing pressures of the ocean floor up to the chilly low pressures of clouds. However, recreating these conditions elsewhere are, in academic vernacular, not trivial. And that’s an understatement.

From Red to Blue

The most discussed target for our first terraforming operation is Mars. Our little red neighboring world is arguably inside the sun’s “habitable zone,” giving it temperatures not too far below those of Earth. It’s the logical first choice, but the dusty little planet isn’t without its problems though.

First is Mars’ lack of an atmosphere — its surface pressure is nearly one thousandth that of Earth at sea level. While there’s some evidence to suggest some Earth life may survive these pressures, most would simply perish.

As well as needing a much denser atmosphere, Mars would need a lot of water. And I really do mean a lot of water. Earth’s surface is covered by over 1018 metric tons of water — that’s more than one million trillion tons. The surface of Mars is about two sevenths as large as Earth’s, so we’d still need a lot of water before Mars could ever have any true oceans.

Perhaps the most brutal suggestion of how we could thicken the atmosphere of Mars is to slam it with comets! A comet is made up mostly of ices, including water, carbon dioxide, and other greenhouse gasses. This would simultaneously thicken the atmosphere and introduce water to the ground. The heat of an impact would also evaporate plenty of the ice buried beneath the martian soil, releasing even more carbon dioxide. There’s a chance we may even get a taste of this happening next year, if there is indeed a comet on a collision course with Mars.

ANALYSIS: Mars Colonists Will Take Cues From The Wild West

With more carbon dioxide wrapping up Mars like a blanket, the surface would start to warm up. With higher pressures, a warmer environment, and water, then we could start to introduce hardy microbes that could metabolize that carbon dioxide, creating oxygen. As conditions became more Earth-like, more and more complex life forms could be introduced. Ultimately, once they would be able to survive, plants and even animals could be released into the growing Martian biosphere.

Of course, we’d still need to keep Mars warm and prevent all that nice new atmosphere from being lost into space. The existing atmosphere on this dry little planet is already so thin because it has no magnetosphere to prevent solar wind from eroding it away, and its weaker gravity has trouble holding on to all of that gas.

Terraforming and Morality

It’s possible that we have the technology to start terraforming Mars already — although the costs would be prohibitive and it would take a long time to have any effect at all. The practicality is still a subject of much debate. Then there’s the question of whether or not we should even try.

The ethics of terraforming are far from straightforward, and opinions vary wildly. Many consider it our moral obligation as a species to spread life from our world to the rest of our solar system and, eventually, to planets elsewhere. In a sense, this would simply be continuing the legacy of life on Earth and the way it’s already shaped our world. Others argue in favor of conservation and the protection of existing natural environments, with some even labeling the very idea of terraforming to be heretical.

ANALYSIS: Can We Lower Earth’s Thermostat?

Still others take a neutral standpoint, being in favor of terraforming only where no indigenous life already exists instead of displacing it. Should we find life already on Mars, which is fundamentally different to Earth life, they argue it may be better to foster it and nurture whatever frail biosphere the planet already has. However, the counter-argument is that if life in other parts of our solar system hasn’t evolved into any complex forms by now, then there’s a good chance that it never will.

Whether terraforming is indeed virtuous or objectionable remains to be decided, and even if we do decide to terraform a planet, we still don’t truly know how, or if, we can do so. One way or another, though, it may eventually be one of the best ways for us to ensure the survival of both our species and the myriad others on our planet.

Image: Artists conception of four stages in the terraforming of Mars. Credit: Daein Ballard/Wikimedia Commons