Let’s fix Mars.

Of course, the Red Planet is spectacular just as it is. Images from forty years of Mars missions have revealed its stark beauty and rose-tinted rocky grandeur. In its southern hemisphere Mars has ancient cratered highlands similar to the Moon’s, while much of the north consists of plains lower in altitude and geologically much younger. The giant shield volcano of Olympus Mons rises 24 km, three times as high as Everest, above the surrounding plains. Valles Marineris, a huge scar across the face of the planet, is a system of canyons 4,000 kilometers long, ten times the length of the Grand Canyon. Hellas Planitia is an impact basin over 2,000 kilometers in diameter and seven kilometers in depth.

Other canyons, networks of river valleys, stream beds, gullies, channels, layered deposits, deltas and alluvial fans provide strong evidence for flowing water, crater lakes and salty seas in a much warmer and wetter period of Mars’s history. Today, though, Mars is desolate and inhospitable, a cold and arid landscape with no precipitation at all, scoured by giant dust-storms. Unprotected, we’d perish quickly from the low atmospheric pressure and lack of oxygen.

There’s a lot to like about Mars. Its day length is twenty-four hours and thirty-seven minutes, and its axial tilt is 24 degrees, both similar to Earth’s. Mars’s total surface area is comparable to the amount of dry land on Earth, and its gravity is 38% of ours, making it easier to move heavy objects. And it’s nearby; using an elliptical transfer orbit we can be there in nine months.

Some time in the future we might decide we need that dusty red real estate. And if we’re going to live there permanently we might want to make some changes so we can travel around safely. We might want to work in jeans and a shirt with a warm breeze in our face, instead of sweating in a bulky pressure suit. Rather than a lifeless rocky desert, we might need a self-sustaining ecosystem with oceans, rivers, forests, farms.

Such a stunning transformation may be easier than you imagine.

***

Keeping Pressurized and Keeping Warm

Down to basics. For humans to survive and thrive on Mars, we need to change three things.

First, the air pressure. Mars already has an atmosphere, but it’s sparse. On Earth the air pressure at sea level is 1013 millibars. On Mars the mean atmospheric pressure is a paltry six millibars, way too low for human survival.

Next: Temperature. The mean surface temperature on Mars is –63^o Celsius, with lows perhaps reaching–140^o C. Antarctica is cold. Mars is really, really cold.

Finally, the atmospheric composition. Earth’s air is 78% nitrogen and 21% oxygen, with traces of argon and carbon dioxide. The Martian atmosphere is 95% carbon dioxide, 3% nitrogen and 1.6% argon, with traces of oxygen and methane. If you happen to be an oxygen-breather, you can see the problem here.

As it turns out, all three of these are fixable with technology that we either have now, or could develop within decades. That’s because the basic ingredients are already in place. Recent missions to Mars have discovered substantial deposits of water ice at the poles and as permafrost underground, equivalent to thousands of cubic kilometers of water. Just as important are the considerable reserves of carbon dioxide (CO₂), some bound up in the polar icecaps, and even more adsorbed in the Martian regolith (soil) at high latitudes. Even using conservative estimates, liberating all that CO₂ could raise the atmospheric pressure on Mars from its current puny six millibars to a much more respectable 300-500 millibars. While we can’t breathe CO₂, we would no longer need pressure suits to keep us alive.

So, what would it take to free all this water and CO₂? A well-placed miracle? No. In fact all it takes is a modest temperature increase of 5 ^o Celsius. Five degrees, and the carbon dioxide at the Martian polar caps starts to sublime and thicken the atmosphere. After that, positive feedback is our friend. Heating the Martian atmosphere helps to thicken it, and thickening the atmosphere helps to heat it. By now this might sound familiar, and so it should: We’re talking about initiating a runaway greenhouse effect on Mars.

There are two sane ways of heating the surface of Mars.

The first is a huge orbital mirror, to reflect and focus sunlight onto the Martian south pole. To achieve a 5 degree rise in temperature over a broad, low-latitude area and begin sublimating CO₂ we’ll need a mirror with a radius of about 100 kilometers. Even if we make this from the same lightweight aluminized mylar we use for solar sails it’ll weigh 200,000 tonnes. We’ll need to construct it in space, but the raw materials are on hand in asteroids or the Martian moons. The mining and construction are the only hard parts, because we already have the basic technology. In 2010 the Japanese deployed a 200square meter solar sail on the IKAROS spacecraft and sent it off towards Venus. NASA, the Russians and the British are all actively working on solar sail materials and their deployment.

The second method brings the industrial revolution to Mars by setting up factories to manufacture chlorofluorocarbon gases (CFCs). These CFCs will create the greenhouse effect we’re after. To generate a Mars-wide temperature rise of 5 degrees our factory would need a power requirement of 1,300 megawatts over twenty years. For comparison, a typical Earth-based nuclear power plant produces about 1,000 megawatts. As before, while the remote location of Mars makes building such a factory challenging, the technology is within our grasp and requires no leaps of faith.

Either approach will radically change the Martian climate within decades. Once kick-started, the ensuing release of CO₂ and the positive feedback loop of the greenhouse effect leads to an eventual temperature rise of about 70^o Celsius. Air pressure soars. The polar ice-caps start to melt, and the northern basins begin to flood. Liquid water returns to the Martian surface, to stay.

Even more dramatic methods are possible. Ammonia is a powerful greenhouse gas, and asteroids may contain billions of tons of it. We might capture a few such asteroids from the outer solar system, propel them towards Mars, and crash them onto the plains. In addition to providing huge amounts of volatile ammonia, the heat generated would warm the atmosphere and free up nitrates from the Martian soil. The downside is that a substantial asteroid impact packs the same punch as tens of thousands of megaton hydrogen bombs, a cataclysm that could delay human colonization of Mars for decades. This method also requires more speculative technologies, and a considerable amount of time.

***

Making Mars Breathable

So, a combination of orbiting mirrors and halocarbon factories, plus a few decades of global warming, will gently produce a Mars where we can walk around in regular clothes carrying our trusty breathing apparatus. That’s a great start. Next we need to activate the hydrosphere, oxygenate the planet, and install a sustainable ecosystem.

We’ll seed the Martian soil with anaerobic bacteria that can produce ammonia and methane from the existing water, carbon, nitrogen and phosphorus. Such bacteria will increase the fertility of the soil and release additional global-warming gases. Breeds of primitive, hardy plants can already thrive in the CO₂-rich atmosphere. We’ll add nutrients and organic content gradually, lichen and algae first, then fungi. Our space mirrors are still helping to raise the temperature, remember, and the amount of liquid water on the surface is continuing to increase. As we propagate our scrubby plants across the Martian surface and seed the incipient oceans with bacteria and algae (in this case, seaweed), our plants photosynthesize CO₂ into oxygen. We might genetically engineer new species of plant to thrive in Martian soil and produce oxygen more efficiently, but even if we don’t it’s just a matter of time before we progress to more advanced plants, and eventually trees.

With continued warming and the greening of Mars, we can generate air sufficiently oxygen-rich for humans and animals in under a thousand years. In a little less than a millennium you could be kicking back on a Martian seashore with lush tropical vegetation at your back and a drink in your hand.

Fixing Mars. It’s within our grasp.

***

Assessing the Rest of the Solar System

Mars may be practically begging to be terraformed, but the rest of the neighborhood is not so easy.

Venus at present seems to be the anti-Mars. Rather than stimulating planetary warming, we’d have to damp out the existing runaway greenhouse effect. First, we’d need to establish immense solar shades between Venus and the Sun, or install reflective materials into Venus’s upper atmosphere, to shield its surface and reduce its searing mean temperature of 460^o C. Then we’d have to devise some innovative means of sequestering the massive amounts of CO₂ in the dense Venusian atmosphere. While Mars is a welcoming, and relatively easy-to-make future home, Venus is a daunting prospect, and may not be worth the effort.

Saturn’s moon Titan has large amounts of available water ice, lakes of hydrocarbons at the poles, and an existing nitrogen atmosphere, but its frosty –180^o C temperature makes warming it a challenge. Jupiter’s moon Europa has a very thin oxygen atmosphere and an icy crust with liquid water beneath, but similar difficulties with the chill factor. Of Jupiter’s other Galilean moons, Ganymede and Callisto are composed largely of rock and water ice and may hold promise for terraforming once we’ve licked the temperature issue.

However, at this point we may as well make our way out of the Solar System altogether, and head out to perform our alchemy on planets around other stars. Because, if we can achieve such ambitious planetary engineering close to home, it’s not unreasonable to assume we will break the bounds of the Sun altogether and truly leave the nest.