It's a nightmare mass extinction event that scientists are racing to avoid and Hollywood loves to portray in Doomsday disaster movies: an asteroid impact that destroys Mankind and wipes out most life on Earth.
Now space scientists suggest such a terminal event may be averted using a one-megaton nuclear bomb propagating a powerful shockwave that would push the incoming monster away.
The plan is one of the few that could be employed in the event that a dangerous space object that could threaten the Earth is only discovered mere weeks or months before impact.
Many countries, including the United States and Russian Federation, have been pushing for a planetary defense system against Near Earth Objects (NEOs) that could present varying degrees of danger to Earth. Some NEOs—about 300 to 500 feet across—are only large enough to potentially vaporize a city. Other NEOs have mass and speeds capable of converting enough kinetic energy to destroy a continent if they impact on land, or create a supersonic tsunami if they crash into the ocean.
The planet killers—those with a mass large enough to destroy Earth's biosphere—have impacted in the past. At least two mass extinction events were triggered by such impacts, one killing off the dinosaurs when a six mile wide asteroid struck precipitating the Cretaceous–Tertiary extinction event and creating the Chicxulub crater off the Yucatan Peninsula some 65 million years ago .
Scientists know it's only a question of time before the next such impact occurs.
While astronomers and astrophysicists recognized the planetary danger from NEOs decades ago, most governments around the world were slow to react.
U.S. Representative George E. Brown, Jr. was one of the first U.S. officials to support an effort to protect Earth from catastrophic space events. Brown had a keen interest in anything scientific and once said, "I was interested in science before I even knew what science was."
The Air & Space Power Chronicles quoted Brown's strong support for projects designed to protect the planet from space threats: "If some day in the future we discover well in advance that an asteroid that is big enough to cause a mass extinction is going to hit the Earth, and then we alter the course of that asteroid so that it does not hit us, it will be one of the most important accomplishments in all of human history."
Strategies to avoid Doomsday
The great majority of strategies to avoid NEO Doomsday events rely on early detection of the threat. Most defense methods require years—even decades—to work.
Ideas that propose ways to avert NEO impacts fall into two categories: delaying the impact or destroying the object. Each approach has plusses and minuses.
Destroying the object with a nuclear explosion may not fully vaporize an asteroid or comet. If the result of such a blast just breaks the NEO into thousands of fragments all will impact the Earth and conceivably cause a rain of flaming death across much of the world. Theoretically the event could be as bad—or worse—than an all-out nuclear war.
Another strategy called a "kinetic impact" basically nudges the object incrementally. While the difference in the object's trajectory is very slight, if done years in advance the NEO would miss Earth by millions of miles.
Steering the dangerous object away with ion rockets is suggested by C.Bombardelli and J.Peláez from the Technical University of Madrid. The two scientists call their concept the "Ion Beam Shepherd."
Former NASA astronauts Edward T. Lu and Stanley G. Love envision a project that would launch a very large robotic rocket to rendezvous with the NRO. If the mass of the rocket were big enough, the gravitational effect would slowly change the orbital path of the object. To be effective, the dangerous object would have to be detected many years in advance.
Many other ideas have been advanced, some relatively simple, others exotic like mass drivers and solar sails.
The Los Alamos anti-asteroid shockwave defense
The approach to deflect incoming NEOs away from Earth that has been conceived by a team at the Los Alamos National Laboratory is adaptable to defending against threats that are detected so late that only a short time remains before impact.
Running out of time to avert a planetary catastrophe is one of the greatest worries those working to save Earth from future space threats have.
The facility in New Mexico, a part of the United States Department of Energy, used the power of a supercomputer to test the feasibility of detonating a one-megaton atomic bomb creating a shockwave powerful enough to change an approaching NEO's orbit. The 32,000 processors of the Cielo supercomputer, working with a 3D model, churned through the problem given it and spit out a positive result: the idea works beautifully.
The simulation revealed a one-megaton explosion near an approaching 1,650-foot-long asteroid would deflect it enough to save Earth.
The required blast is roughly 50 times more powerful than the detonation of the Fat Man atomic weapon that occurred in the closing days of WWII over Nagasaki, Japan. Delivering the nuke and detonating it near the target are well within existing technological capability.
The encouraging results are explained in a video released by the Los Alamos lab. The video appears on Youtube.
In the video presentation, Bob Weaver, a Los Alamos researcher, explains that, “Ultimately this one-megaton blast will disrupt all of the rocks in the rock pile of this asteroid, and if this were an Earth-crossing asteroid, would fully mitigate the hazard represented by the initial asteroid itself."
The new defense strategy comes none too soon as several NEOs have a chance of hitting Earth over the next 50 years.