Mad about Science: Civilization killers

By Brenden Bobby
Reader Columnist

I am a ’90s dinosaur kid. That means for a third of my life, one thing in the world really scared me: planet-killing asteroids.

In an age before the terror attacks of 9/11 but after the fall of the Soviet Union, there was one unifying fear in the American cultural zeitgeist and that was civilization-ending asteroids. They were mysterious, faceless boogeymen from the stars that could strike at any moment and lay waste to everything people had worked so hard to build.

Movies like Deep Impact and Armageddon romanticized the idea of man versus nature, using grit, gumption and scientific know-how to save lives with complex plans and acts of sacrifice and heroism.

Apocalyptic asteroids aren’t exactly a new concept for Earth, but they are for human civilization. During the formation of Earth, the planet was consistently bombarded with fragments of molten rock ranging in sizes from a family sedan to something comparable to Mars. 

According to the “giant-impact hypothesis,” the formation of the moon may have resulted from a Mars-sized protoplanet referred to as Theia that impacted a young Earth about 4.5 billion years ago, causing both planets to break into a massive cloud of swirling molten rock that later coalesced into the two distinct bodies we know today.

Smaller asteroid impacts could be a different story, and it’s likely that the dinosaurs weren’t the only creatures driven to extinction by large scale asteroid impacts.

The triggering event that led to the extinction of the dinosaurs 65 million years ago was the 6.2-mile-wide asteroid that formed the Chicxulub crater in Mexico’s Yucatan Peninsula. 

By the time this asteroid impacted Earth, it was traveling at a speed of about 12 miles per second — more than 56 times the speed of sound. This released an absurd amount of energy in the form of superheated shockwaves so powerful that granite at the center of the impact site instantly shifted into a liquid state.

Much of that material blew outwards, but a central impact peak of molten granite rose as high as six miles before falling back into the impact ring. This would not have been visible to the dinosaurs as the impact likely appeared as blinding white light, like staring into the sun. In addition, colossal amounts of debris were ejected into the atmosphere, which caused a heat wave to strike Earth while igniting global wildfires as molten ejecta rained down across the globe.

Humans have a relatively strong presence in space, which gives us a tremendous edge over planet-killers that wiped out the dinosaurs. But how would we go about preserving mankind from giant  rocks traveling tens of thousands of miles per hour?

Asteroids, while appearing as large rocks, are not entirely solid. They can often be porous or are a collection of different kinds of rocks that have congealed beneath a rocky exterior membrane. You can think of a lot of asteroids like a collection of gravel in a flying sack. This is important when it comes to countering a planet-killer.

Movies like Armageddon have us believe that the strongest tool in our arsenal is a nuclear warhead. It makes sense, right? Use a huge amount of energy to counteract a huge amount of energy in hopes of blasting it into nothingness or redirecting it. Unfortunately, this isn’t viable. A nuclear weapon’s greatest strength on Earth is the atmosphere. Superheating air allows the heat to travel farther and creates powerful shockwaves of heated air. A nuke in space just throws the energy everywhere and dissipates, which does very little to redirect an asteroid.

Instead, one of the most powerful tools we as humans can use somewhat resemble the “Czech hedgehogs” of World War II — the metal tank barriers that were scattered along the beaches of Normandy to stall the Allied invasion. Scientists have designed long, pin-like structures made of tungsten steel that can be launched into space to create a minefield for incoming asteroids. The asteroid impacts the needles, which tear open the membrane and cause the rock inside to scatter into innumerable smaller pieces that can act like a midsummer meteor shower in the atmosphere.

What if the asteroid or comet is bigger? Much bigger?

A single tungsten lance would create so much heat energy from the impact and friction that the steel would melt and evaporate before the mass could break up. More of these would need to be utilized and lined up perfectly to strike one after another to dig deeper into the planet-killer. A sufficiently large object would also require a nuclear payload, which is normally useless in space, to be delivered deep into the core of the object and then detonated so that the energy is transferred to the surrounding structures to break the beast apart from the inside out.

This would also have to be done before the object passes Mars, which could be considered a nearly impossible feat and still presents the danger of peppering the inner solar system with scattered debris that would be virtually impossible to track.

Objects in space don’t travel in a straight line. They travel in an orbit around the sun or other celestial bodies. As the objects approach the sun, their speed increases as they are effectively falling toward the center of gravitational pull. This means that objects like planet-killers are reaching their maximum velocity right around the time they’re nearing the Earth, due to our proximity to our home star.

One could argue it reaches its peak speed moments before interacting with Earth’s atmosphere, so long as it’s on a collision course with us.

Stay curious, 7B.