Too late to duck

Russell Schweickart has an article in The New York Times about asteroids:

A few weeks ago, an asteroid almost thirty feet across and zipping along at 38,000 miles per hour flew 28,000 miles above Singapore. Why, you might reasonably ask, should non-astronomy buffs care about a near miss from such a tiny rock? Well, I can give you one very good reason: asteroids don’t always miss. If even a relatively little object was to strike a city, millions of people could be wiped out.
Thanks to telescopes that can see ever smaller objects at ever greater distances, we can now predict dangerous asteroid impacts decades ahead of time. We can even use current space technology and fairly simple spacecraft to alter an asteroid’s orbit enough to avoid a collision. We simply need to get this detection-and-deflection program up and running.
President Obama has already announced a goal of landing astronauts on an asteroid by 2025 as a precursor to a human mission to Mars. Asteroids are deep-space bodies, orbiting the Sun, not the Earth, and traveling to one would mean sending humans into solar orbit for the very first time. Facing those challenges of radiation, navigation, and life support on a months-long trip millions of miles from home would be a perfect learning journey before a Mars trip.
Near-Earth objects like asteroids and comets— mineral-rich bodies bathed in a continuous flood of sunlight— may also be the ultimate resource depots for the long-term exploration of space. It is fantastic to think that one day we may be able to access fuel, materials, and even water in space instead of digging deeper and deeper into our planet for what we need and then dragging it all up into orbit, against Earth’s gravity.
Most important, our asteroid efforts may be the key to the survival of millions of people, if not our entire species. That’s why planetary defense has occupied my work with two nonprofits over the past decade.
To be fair, no one has ever seen the sort of impact that would destroy a city. The most instructive incident took place in 1908 in the remote Tunguska region of Siberia, when a 120-foot-diameter asteroid exploded early one morning. It probably killed nothing except reindeer, but it flattened 800 square miles of forest. Statistically, that kind of event occurs every 200 to 300 years.
Luckily, larger asteroids are even fewer and farther between, but they are much, much more destructive. Just think of the asteroid seven to eight miles across that annihilated the dinosaurs (and 75 percent of all species) 65 million years ago.
With a readily achievable detection and deflection system, we can avoid their same fate. Professional (and a few amateur) telescopes and radar already function as a nascent early warning system, working every night to discover and track those planet-killers. Happily, none of the 903 we’ve found so far seriously threaten an impact in the next one hundred years.
Although catastrophic hits are rare, enough of these objects appear to be or are heading our way to require us to make deflection decisions every decade of so. Certainly, when it comes to the far more numerous Tunguska-sized objects, to date we think we’ve discovered less than a half of one percent of the million or so that cross Earth’s orbit every year. We need to pinpoint many more of these objects and predict whether they will hit us before it’s too late to do anything other than evacuate ground zero and try to save as many lives as we can.
So, how do we turn a hit into a miss? While there are technical details galore, the most sensible approach involves rear-ending the asteroid. A decade or so ahead of an expected impact, we would need to ram a hunk of copper or lead into an asteroid in order to slightly change its velocity. In July of 2005, we crashed the Deep Impact spacecraft into comet Tempel 1 to learn more about comets’ chemical composition, and this proved to be a crude but effective method.
It may be necessary to make a further refinement to the object’s course. In that case, we could use a gravity tractor: an ordinary spacecraft that simply hovers in front of the asteroid and employs the ship’s weak gravitational attraction as a tow-rope. But we don’t want to wait to test this scheme when potentially millions of lives are at stake. Let’s rehearse, at least once...
The White House Office of Science and Technology Policy has just recommended to Congress that NASA begin preparing a deflection capacity. In parallel, my fellow astronaut Tom Jones and I led the Task Force on Planetary Defense of the NASA Advisory Council. We released our report a couple of weeks ago, strongly urging that the financing required for this public safety issue be added to NASA’s budget.
This is, surprisingly, not an expensive undertaking. Adding just $250 million to $300 million to NASA’s budget would, over the next ten years, allow for a full inventory of the near-Earth asteroids that could do us harm, and the development and testing of a deflection capacity. Then all we’d need would be an annual maintenance budget of $50 million to $75 million.
By preventing dangerous asteroid strikes, we can save millions of people, or perhaps even our entire species. And, as human beings, we can take responsibility for preserving this amazing evolutionary experiment of which we and all life on Earth are a part.
Russell Schweickart, a former astronaut (known then as Rusty), was the co-chairman of the Task Force on Planetary Defense of the NASA Advisory Council.

Rico says he wouldn't want to be the one to explain to the few species surviving a major impact why we weren't willing to spend a couple hundred million dollars (not billions, though it'd be worth it) to save the planet...