Imagine this: NASA scientists have predicted an asteroid will soon slam into Earth. It would be more than a mile wide, traveling at about 20,000 miles per hour. The impact would be comparable to 2 million atomic bombs. Hitting the ground would turn whole cities into craters. Hitting the ocean could cause a Tsunami wave hundreds of feet in height. The dust in the air would cause months of darkness. What exactly should you do with information about a giant speeding rock careening toward Earth?
Basically, nothing. It’s probably just the plot of a movie. “There are millions of asteroids out there in orbits that do come close to Earth’s orbit, and impacts have happened many times in Earth’s past, and it will happen again in the future. It’s just a matter of when,” Lindley Johnson, NASA’s asteroid expert and director of its Near-Earth Objects Program, explained to American Survival Guide.What is an Asteroid?
Call it a speeding rock in space, or call it a small planetary body and one without an atmosphere. Asteroids are usually found orbiting the sun in what’s called the Main Asteroid Belt between the orbits of Mars and Jupiter. According to NASA, asteroids are thought to be “primordial material prevented by Jupiter’s strong gravity from accreting into a planet-sized body when the solar system was born 4.6 billion years ago.” The first—and largest—asteroid, Ceres, was discovered in 1801. “An asteroid less than about 30 feet in size is commonly called a meteoroid while still in space before it hits Earth’s atmosphere, becoming a meteor that burns up on entry before it hits the surface,” explained Johnson. Asteroid impact is what scientists consider a very low probability, but high-consequence event.
“Once a year, there’s a car-size asteroid that does hit Earth’s atmosphere and makes a fire-ball spectacle of itself, then burns up before reaching the surface. And every 2,000 years or so, an asteroid about football-field size does hit Earth and causes catastrophic damage to the impact area. But it’s only about once in a million years that something large enough hits Earth to threaten civilization. NASA’s team sets out to find any asteroid that might pose an impact hazard to Earth, and to know that information far enough in advance to do something about it. Scientists detect any asteroids in Earth-approaching orbits, “and then we do what we call propagate the orbit,
which is to predict the movement of those objects well into the future,” Johnson said. “In fact, we’re pretty high precision now to 100 years in the future of where that asteroid will be in relation to where the Earth is, and not only the Earth, but also for all the major bodies in the solar system.” The group has already found pretty much the entire population of large Earth-approaching objects out there, anything bigger than three-quarters of a mile across, even knowing how big and small they are. “As of today, we are tracking some 11,508 near-Earth asteroids,” noted Johnson. “Any asteroid that would be the size that would annihilate Earth, we have already found.” But he also noted that there are estimated to still be tens of thousands of asteroids larger than a football stadium that can come near Earth and are still undiscovered.
Here’s the thing: Earth is impacted by stuff every day (like those meteor showers we rush to watch), and the planet also collects about 100 tons of material a day, like sand and dust coming in from space. And Mother Earth does a pretty good job of protecting herself. “The object is moving so fast, the molecules in the Earth’s atmosphere can’t really get out of the way so they build up pressure and cause friction on the object.
Enough heat and friction on a smaller object in the atmosphere cause it to break up, explode, and disintegrate before it hits the surface,” Johnson explained. “But a larger object coming at a high velocity, its internal strength is greater than what the atmosphere can handle, so it is able to make it all the way through the atmosphere before that pressure and heat build up to the point that it explodes.”
“As of today, we are tracking some 11,508 Near-Earth Asteroids.”
The way in which we’re most likely to survive a true asteroid threat is based on the fact that scientists, once the object is found by telescopic surveys, can predict where it would hit the Earth’s surface and would then be able to evacuate the area, similar to the preparation for a hurricane that’s heading for the coast. But there are high-tech procedures that could prevent this from happening while the asteroid is still in space.
It works like this: They find an object that might be an impact threat many years—if not decades—before possible impact and put a force upon it that either increases its speed slightly or decreases its speed slightly. “You only have to change the velocity of an object maybe an inch per second many years in advance and by the time that it gets to where it would have impacted Earth, it’s in a completely different place in its orbit,” explained Johnson. Smaller objects, say 300 feet wide, can be hit with a spacecraft at a relative velocity to it, like eight miles per second—the kind of velocity orbital trajectories have. This technique is called kinetic impactor, and it will slow down the object, and then several years later when it would have impacted Earth, it will be in a different place of its orbit. Scientists could also utilize a spacecraft for something called gravity tractor, “where we hover in what we call a halo orbit in front of or behind the asteroid, and mutual gravity attraction between the spacecraft and the object will eventually change its velocity and have the same effect as the kinetic impactor.”
However, if there isn’t enough time for these techniques to have an effect, then to get a spacecraft to the object to be able to deflect it or disrupt it, a nuclear device could be used. In December 2005, President Bush signed into law the NASA Authorization Act (also called the George E. Brown Jr. Near-Earth Object Survey Act), which stated, “the objectives of the George E. Brown, Jr. NEO Survey Program are to detect, track, catalogue, and characterize the physical characteristics of NEOs equal to or larger than 140 meters in diameter with a perihelion distance of less than 1.3 AU (Astronomical Units) from the sun, achieving 90 percent completion of the survey within 15 years after enactment of the NASA Authorization Act of 2005.”
The study team “assessed a series of approaches that could be used to divert a NEO potentially on a collision course with Earth. Nuclear explosives, as well as non-nuclear options, were assessed,” and “nuclear standoff explosions are assessed to be 10-100 times more effective than the non-nuclear alternatives analyzed in this study. Other techniques involving the surface or subsurface use of nuclear explosives may be more efficient, but they run an increased risk of fracturing the target NEO. “There’s certainly no reason to panic that the earth is going to be hit by an asteroid anytime in the near future,” Johnson explained. “We are tracking objects that are in orbits that approach the Earth, but none have significant probability of impacting the earth in the next 100 years.”Asteroid Dangers,1908-2029
There was a pause heard round the world in 2004 when an asteroid about 1,000 feet wide was spotted on an orbit that comes close enough to Earth that initially it was calculated to have some probability of smashing into us in April 2029—Friday the 13th, in fact. Its official designation was 2004 MN4, although the discoverer named it Apophis after the Egyptian god of destruction. Back in 2005, Paul Chodas, an orbit analyst with NASA’s Near-Earth Object office responded, “We weren’t too worried, but the odds were disturbing.”
“…it was calculated to have some probability of smashing into us in April 2029 — Friday the 13th, in fact.”
The object thought to wipe out Earth and dinosaurs 65 million years ago was estimated to be about six miles in size, “but we certainly would know of any object that size now, and there are none that big that will impact the Earth any time in the foreseeable future nor thousands of years into the future, as a matter of fact,” Johnson explained.
The Barringer Crater in the Arizona desert is a recent example of impact on Earth, although by recent, it’s estimated to be 50,000 years old. The 640-plus-foot-deep and mile-wide crater was caused by an approximately 150-foot-wide, 300,000-ton asteroid. Something like that “hitting close to a metropolitan area would do a lot of damage and there would be a lot of casualties,” Johnson said.
In 1908, an asteroid about 100 feet in diameter blew up over a remote part of Siberia, destroying more than half a million acres of forest. And in 1989, an asteroid about a quarter-mile wide and cruising at 24,000 mph came about 450,000 miles from Earth. Scientists believed the asteroid and Earth had actually passed through the same point in space by a difference of just six hours.
Editor’s note: A version of this article first appeared in the Doomsday 2016 issue of American Survival Guide.