Heating Mars On The Cheap [Hackaday]

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Mars is fairly attractive as a potential future home for humanity. It’s solid, with firm land underfoot. It’s able to hang on to a little atmosphere, which is more than you can say about the moon. It’s even got a day/night cycle remarkably close to our own. The only problem is it’s too darn cold, and there’s not a lot of oxygen to breathe, either.

Terraforming is the concept of fixing problems like these on a planet-wide scale. Forget living in domes—let’s just make the whole thing habitable!

That’s a huge task, so much current work involves exploring just what we could achieve with today’s technology. In the case of Mars, [Casey Handmer] doesn’t have a plan to terraform the whole planet. But he does suggest we could potentially achieve significant warming of the Red Planet for $10 billion in just 10 years.

Giga-Scale Production

Handmer doesn’t hope to give Mars a comfortable climate and fully breathable atmosphere in one go. Instead, the idea is first to warm Mars up significantly and release additional carbon dioxide. The hope is that this would help create a warmer blanket around the planet as a starting point for further terraforming works. His plan involves no nuclear reactors, chemical seeding, or big mining operations. Instead, it’s about maximising the amount of heat pumped into Mars for the lowest cost.

The concept is simple. By increasing the amount of sunlight falling on to Mars, its temperature can be increased significantly. That additional warmth would ideally release CO2 from cold storage in carbonate deposits already on  Mars. This would further accelerate warming just as it does on Earth via the Greenhouse effect. Ideally, pump enough heat in initially to get that CO2 into the atmosphere, and our favorite greenhouse gas might just do the rest.

To get more sunlight on Mars, Handmer proposes using solar sails. Not just one, or two, or a hundred, but solar sails in their billions. They would use light from the sun to travel from Earth to Mars on a timescale of months. When arriving at Mars, they would be stationed at the Sun-Mars L2 Lagrange point, where the required orbital corrections would be at a minimum. From that point, the solar cells would position themselves to reflect sunlight on to the Martian surface to provide heating.

The sun already provides energy on the level of roughly 600 watts per square meter on the Martian surface. That sums up to about 21,600 terawatts across the entire planet. Compare that to the 8 gigawatts or so put out by our largest nuclear reactor, and it’s easy to see the sun is providing a lot more energy than we could hope to achieve with any kind of operation on the Martian surface. Reflect more of that sun, and that number goes up nicely.

Handmer notes that a reflector covering 1,000 square meters would reflect 600 kW of sunlight towards Mars. 1,000 sails of this size would effectively add a square kilometer of surface to Mars’s existing cross-sectional area of 36,000,000 square kilometers. That’s not really a whole lot.

As mentioned above, the key is to scale into the billions. The idea is that these simple solar sails could be manufactured on the cheap. Handmer posits that a 1,000 gram sail craft could cover the aforementioned 1,000 square meters. He estimates a production cost on the order of $100, roughly equivalent to a modern cellphone. For electronics, the sail would need a processor, a telemetry radio, a small solar panel, and a camera to act as a star tracker for navigation. It would then use LCD panels to act as reflectively-variable elements to change its direction under the influence of the sun. At that weight, launch costs would be around $2000. Add that on to the manufacturing cost, and you’ve got 1,000 square meters of Mars reflector for just $2100. Advances could shave manufacturing costs and weight down further, slashing launch costs which are heavily weight dependent.

If these solar sails could be manufactured with the same efficiency we churn out smartphones, we could churn out hundreds of millions of these craft in a few years. Handmer suggests a decade of launches could net 1.5 billion sails in position around Mars, which would be good enough for increasing energy input to the planet by 4%. In turn, Mars’ thermal radiation would have to increase by 4% to balance this extra energy input, which suggests its basic temperature would rise from 210 K to 212 K—or roughly -61.15 Celsius.  He costs all this out at around $10 billion, which sounds awfully cheap in the grand scheme of things.

Worth It?

Okay, so that still sounds terribly cold. And it is! But that rise of two degrees isn’t to be sniffed at. As Handmer points out, that’s more than we’ve achieved here on Earth in 250 years of rampant fossil fuel use.  He also notes that the shining solar sails would make for a brilliant view from Mars’s surface, though it’s perhaps unlikely many humans would be there to see it, at such cold temperatures.

Further gains could be made with some strategy. If cold deposits of stored carbon dioxide were spotted on the surface, the sail network could ideally be aimed to some degree to prioritize warming of those areas first. Done right, this could speed temperature rises on Mars quite significantly.

Reality Check

It’s a brilliant idea, and one we’d like to see explored further. At the same time, it’s unlikely to get real legs any time soon. There’s little will to terraform Mars right now, given we haven’t even sent a human over for look just yet.

Furthermore, even if Mars was warmed significantly, there’s still the question of whether the atmosphere and environment could be made livable. Humans need oxygen, and we like a certain atmospheric pressure and lots of water. Getting Mars into the right ball park on all these measures would be tough, and maintaining it would involve countering the effects of the solar wind, which has stripped the planet’s atmosphere in the past.

The plan also glosses over some finer points of the engineering required. It’s one thing to build 1.5 billion solar sails, and another thing entirely to launch them all and get them to Mars. Once there, they’d need to be very well organized to avoid crashing into each other and turning into one big tangled blob in orbit.

Handmer has put together a very compelling plan to warm Mars, and to do it on the cheap. Whether it would work is an open question, but this is the kind of wide-ranged blue-sky thinking that’s required to solve the space-based problems of tomorrow. Terraforming an entire planet isn’t something you do on the small scale; it’s something that requires the massed industrial outputs of entire societies. That’s a lesson we must learn, not just on Mars, but on Earth.