Hollywood films have dramatized an event that scientists say could one day happen. An asteroid approaches the earth, threatening the planet, and a team of daring astronauts travels to space to stop it. Some scientists and engineers say the films were not realistic, but that the threat is real.

In the 1998 film Armageddon, Bruce Willis and his team landed on an asteroid and used a nuclear weapon to destroy it. Scientists say the movie was not accurate in its science, but that its central premise was authentic. An asteroid could one day strike the earth with devastating results.

In the past 600 million years, collisions with space objects have caused five mass extinctions. The best-known collision, 65 million years ago, helped kill off the dinosaurs. But the worst, nearly 200 million years before that, eliminated more than 90 percent of life on the planet. More recently, the 1908 explosion of an asteroid over Siberia flattened 2,000 square kilometers of forest.

Two years ago, a group of scientists, engineers, and astronauts created an organization to prevent another cosmic collision. Called the B612 foundation, it takes its name from the asteroid that was home to the fictional Little Prince in the story by French writer Antoine de Saint-Exupery.

Former astronaut Rusty Schweickart, chairman of the foundation, spoke about its goal at the Planetary Society in Pasadena, California. "To deflect an asteroid in a controlled manner by 2015. And we're not saying to write a paper about it, to think about it, to talk about it. We're saying our goal is to deflect an asteroid, that is, to move an asteroid, to change its orbit, by 2015," he says.

Mr. Schweickart was the lunar module pilot on the Apollo Nine mission in 1969, and he is urging the U.S. space agency, NASA, to support the deflection project.

He says it could be incorporated into an existing NASA program called Prometheus, which will send a nuclear-powered spacecraft to explore three of Jupiter's icy moons, and has a scheduled launch date of 2011 or later.

Scientists believe there are more than 1,000 near-earth asteroids at least one kilometer in size, but the likelihood is low that one that big will hit earth in the near future. So Mr. Schweickart wants the demonstration done on a smaller asteroid. "The smaller they are, the more frequent, therefore we pick not the crowd-killer of a one kilometer or something like that. It's only going to come once every million or two million or 10 million years. Instead, we wanted to pick something that was relatively frequent, a 200 meter object," he says.

A collision of an object of that size with the earth would cause a blast equivalent to hundreds of megatons of explosives.

Advocates of the project say an asteroid can be deflected to a safer trajectory with a tiny nudge of less than one centimeter per second, if the mission is undertaken at least a decade before the projected collision.

An Asteroid impact destroys Paris in the 1998 film Armageddon - Courtesy: Touchstone Pictures

In the movie Armageddon, the astronauts used a nuclear bomb to destroy the approaching asteroid, but that, says Mr. Schweickart, is not a good idea. Most 200 meter asteroids are piles of rubble, and one or more of the pieces could hit the planet. Moreover, says Dan Durda, senior scientist with the Southwest Research Institute, asteroids are rich in minerals and offer opportunities for extraterrestrial mining. "You can't mine an asteroid by nuking it. The same technologies that we're going to be demonstrating or hope to demonstrate in this particular case to move or deflect an asteroid to protect the planet, are exactly the same technologies and capabilities and techniques that we're going to be using to move an asteroid around the solar system to mine them and utilize them for their resources," he says.

It is not likely a large asteroid will collide with earth soon, but Mr. Schweickart and his colleagues say it is only a matter of time before one hits us. They add that for the first time in our planet's history, we have the technology to prevent it.