Collecting Killer Asteroids in Earth Orbit

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A couple weeks ago I wasn’t far from “ground zero,” with asteroid hunter Dave Trilling of Northern Arizona University. I’m not referring to any site of a terrorist attack, but rather a marauder from deep space.

About 50,000 years ago, a meteorite one-and-a-half times the length of a football field slammed into the Colorado plateau, unleashing the energy of 150 Hiroshima atomic bombs.

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The awareness of the gaping mile-wide impact crater it left behind near Flagstaff, Ariz., made the conversation with Trilling all the more relevant.

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He estimated that there are 10 million asteroids bigger than the lunch table we were sitting at. Thankfully, something the size of the Arizona meteorite comes along only about once every 30,000 years.

Trilling has used NASA’s Spitzer Space Telescope to do a census of asteroids. He finds that asteroids are a mixed breed. They can be as white as snow or black as tar. Bright ones are rogue comets. The darkest are mostly made up of organic compounds. They range in density such that some would float in a bathtub, while others are more like a ball of solid iron.

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Trilling doesn’t know why the asteroid population is so diverse. “Good science projects give you more questions than answers,” he shrugged. Certainly, there has been a lot of mixing of the primordial asteroids since the birth of our solar system.

Trilling explained that there’s sort of a conveyor belt process where debris from the Kuiper belt — just beyond the orbit of Neptune — fall inward toward the sun. Many pieces of ice get slingshot away when crossing the orbit of the outer planets, like the video game character Frogger trying to cross lanes of traffic.

There’s an emerging view that our planet’s fate in is intimately intertwined with these cosmic interlopers.

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Life appeared on Earth shortly after the last asteroid bombardment four billion years ago. Did the asteroids import water and the necessary organic compounds to Earth for life? Or did the heavy bombardment simply obliterate life until it could only re-emerge after the rocky deluge ended?

Humans are here today thanks to the Cretaceous–Tertiary impact event that turned over evolution’s card table 65 million years ago. This mass extinction allowed for mammals to replace the dinosaurs as rulers of the Blue Planet.

The next global life extinguishing asteroid collision is due within the next 40 millions years — that’s based on statistics, not ridiculous predictions from interpritations of the Mayan calendar.

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Asteroid Farm

But our charge for the future is to not simply to figure out ways of deflecting doomsday asteroids, but instead capturing them for the vast resources they contain. If you park a near-Earth object (NEO) into a tidy Earth orbit, it can’t be a threat anymore, even to Chicken Little.

There have been numerous studies about deflecting asteroids away from Earth, but leave it to the mind of a science fiction writer to imagine the unimaginable — and not be intimidated by the limits of present technology.

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Author and self-described futurist Stephen Covey asserts that an investment of perhaps $20 billion could yield $1 trillion in asteroid resources. That’s a fifty-fold gain, with tremendous benefits for all of humanity, he writes. “We should never forget that capturing a potentially hazardous asteroid converts a dangerous threat into a resource of immense value.”

A well-known Earth threatening asteroid is named Apophis. At the length of an oil supertanker, Apophis will approach Earth to within 16,000 miles on April 13, 2029. (By the way, that happens on a Friday, for superstitious type to sweat over.) Apophis will sweep below orbits of our geostationary satellites. The pesky intruder comes back again in 2036.

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But Covey estimates that if it were snagged and placed into orbit around the Earth it would provide enough material — 27 million tons — to construct about 125 solar power satellites (SPS). They would each generate five gigawatts of energy beamed to Earth ground receivers.

Covey says that the material would also be used to build a cylindrical rotating space habitat for the SPS constructions workers and families, numbering a population of 100,000.

Iron from Apophis could build a radiation shied around the habitat. Oxygen freed from iron compounds would provide breathable air.

Building such a space colony by lofting materials out of Earth’s deep gravity well will never happen because of the cost per payload pound. Even NASA’s Space Launch System is estimated to cost at least $5,000 per pound of payload.

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“I believe that humanity will view Earth-crossing, potentially hazardous asteroids as low-hanging fruit, and each future discovery of an asteroid on a possible collision path will be followed by a gold-rush style race culminating in another new moon for our planet,” Covey wrote.

Even a small asteroid weighs millions of tons. But “warp drive” doesn’t have to be invented or some other form of exotic physics to tow it around. It’s all in the simple application of Newtonian physics.

So, where there’s a political will there’s a way.

Among numerous scenarios, Covey suggests modifying the asteroid’s orbit such that it makes a subsequent close approach to the moon with a relatively low velocity. This can drop that asteroid into a highly eccentric Earth orbit with a nine-day orbital period.

The fuel needed to nudge Apophis via rocket motors would be less than 10 tons, depending on the efficiency of the propulsion engine, he estimates.

Private industry might undertake such a space-mining mission that would be funded by selling electricity to Earth from SPSs. The revenue could be $150 billion per year according to Covey.

But filing a, ahem, environmental impact statement might be problematic. Would countries see captured asteroids as a celestial Sword of Damocles?

Advanced extraterrestrial civilizations might routinely harvest asteroids in this manner. Extraordinarily powerful space telescopes of the far future would be capable of recording transits of numerous small bodies across the face of an exo-Earth.

The only plausible explanation might end up being that they were deliberately placed in orbit about the planet. After much debate, the observations might be accepted as indirect evidence for a technological civilization elsewhere in the galaxy.

Image credits: National Space Society, Space Studies Institute, NASA

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