No, and it’s almost impressive how many ways this could backfire and make global warming worse.
The idea of using a comet to cool the planet, famously featured in the Futurama episode None Like It Hot from 2002, might sound quirky and fun. It plays on the image of dropping an ice cube into a drink to cool it down. However, in reality, this approach wouldn’t work and would actually exacerbate the problem of climate change. Let’s explore why.
One fundamental issue is the immense heat generated when objects fall from space. Think about it: when anything falls, it gains kinetic energy. And when that falling motion stops, that energy has to convert into something else – usually heat. Consider Niagara Falls; as water plunges 50 meters, the kinetic energy gained is enough to warm it by about 0.1°C by the time it reaches the bottom. (Interestingly, evaporation has a cooling effect on the way down, so the actual temperature might be slightly colder).
But space is much higher than Niagara Falls.
The immense fall through Earth’s gravity well means anything coming from space gains a tremendous amount of kinetic energy. An ice chunk from space falling to Earth would gain so much energy it would heat up, melt, boil into vapor, and then superheat that vapor to thousands of degrees – all from the energy of its fall. Imagine a waterfall of ice from space; it would arrive at the Earth’s surface as a river of superheated steam. Smaller ice chunks would completely disintegrate and vaporize high in the atmosphere, warming the upper layers. Larger comets could survive to impact the ground, but then they would vaporize on impact, releasing all that kinetic energy as a massive burst of heat. This heat energy would be about 100 times greater than the energy needed just to warm a very cold comet to room temperature. So, paradoxically, a comet falling from space would heat the Earth about 100 times more than any potential cooling effect it might have.
Let’s put aside the fiery entry for a moment and imagine we could somehow lower a comet gently, perhaps with a magical space crane.
Comets are often visualized as giant snowballs, but they’re actually more like dusty snowballs – a mix of dust and ice, and not very dense. A small piece of comet might float briefly in the ocean, but it would quickly become waterlogged, melt, and break apart. A full-sized comet wouldn’t be structurally sound enough to hold its own weight in Earth’s gravity. It would likely crumble and collapse like a poorly made sandcastle.
Even if we managed to place a comet in the ocean intact, the cooling effect would be incredibly minimal. The added ice would cool the entire ocean by only about a millionth of a degree. If we placed it on land, it might briefly cool the air by a fraction of a degree, but the atmosphere holds far less heat than the oceans.
So, maybe we just need thousands of comets, right? A constant barrage of icy space rocks gently lowered into the ocean?
Unfortunately, there’s another major problem: comets contain carbon dioxide (CO2). As a comet melts, this CO2 is released into the atmosphere. CO2 is a greenhouse gas. It traps heat and warms the planet. Over a few years, the CO2 released from a comet would trap more heat than the ice could ever absorb. Over decades and centuries, this greenhouse effect would accumulate, leading to even more warming. In the long run, the CO2 released from the comet would raise Earth’s temperature as much as if we had simply let it crash into the planet and vaporize instantly. While a slow decay might be better than a high-speed impact (ask any dinosaur), it’s still a terrible climate solution.
But wait, there’s a twist! Your “What If” scenario could actually help fix global warming, just not in the way you initially imagined.
Remember that magical crane we imagined for gently lowering comets? If we hooked that crane up to a generator, we could harness the energy of the slowly descending comet to produce electricity.
A single comet, lowered from space to the Earth’s surface, could potentially supply the entire world’s energy needs for a whole year! Sure, it would release some CO2, but that would be dwarfed by the pollution from our current fossil fuel-based energy sources. A “comet crane generator” could drastically reduce our greenhouse gas emissions from energy production, bringing them close to zero. In this scenario, the comet itself isn’t the solution; the crane is!
Sadly, we don’t have the technology to build giant comet-lowering space cranes, at least not anytime soon to address current climate change. However, this idea of harvesting orbital energy is intriguing! While it might not solve global warming with comets, perhaps someday, far in the future, we’ll face a different problem for which a giant comet crane is the perfect, albeit outlandish, solution.
