2011.03.30 Driving the gravity tractor

Written by David Green.

By DAVID GREEN

Can former astronaut Rusty Schweickart save us from extinction or will we go the way of the dinosaurs? Will we find someone to skillfully drive the gravity tractor or will we merely make things worse?

Those aren’t nice questions to ask on such a pretty, sunny morning. Oh, by the way, did you know that fireballs from space can be seen even on a sunny day like this, in broad daylight?

OK, so I just finished reading an article about NEOs (near-Earth objects). It sets you on edge for a while, but you soon forget about it and don’t even think about the asteroids flashing through our sky every night. Out of sight, out of mind. Unless you’re Rusty Schweickart.

Schweickart is considered a little loony by some people. They say he spent too much time in space and the radiation cooked his brain.

He doesn’t help himself when he makes statements like the following one. He talked to “New Yorker” writer Tad Friend about other space civilizations this way: “If there is a cosmic community out there, they will have already passed this test, of protecting themselves from asteroid impacts that could have wiped them out. If we want to join them, we have to do it, too.”

In other words, a few billion bucks will have to be spent on devising ways to deflect an asteroid that might be on a collision course with Earth.

It doesn’t happen often, but asteroid collisions are blamed by some scientists for three mass extinctions. The imprint of the most famous one is clearly visible in 3-D imaging from space. It’s on Mexico’s Yucatán Peninsula. That one is known as the dinosaur killer.

More recently, there was the mysterious explosion in Siberia in 1908 that flattened 830 square miles of desolate forest. Scientists believe there was no actual impact because there’s no crater. It’s believed that a sizable asteroid blew up before impact and sent an enormous shock wave to the Earth’s surface. That was the last major impact.

In 2008, an asteroid the size of an S.U.V. slammed into the desert in Sudan. Another was clearly visible streaking over Saskatchewan. A year later, one blew up high above Indonesia that was said to have the power of three atomic bombs.

Just last month a rock weighing several tons was seen blazing across the sky. People from Massachusetts to Maryland saw it—in daylight!

So what are we doing about it? We’re thinking. Some of us are worrying. 

NASA budgets about .03 percent of its funds to “planetary defense.” The consequences of a collision are huge, but the odds of it happening are small. This is when they start running the fatality-per-year numbers. The Yucatán incident, by the way, happened about 65 million years ago.

The Planetary Defense task force knows its job is a sticky wicket. You could send up a big bomb in an effort to deflect an asteroid off course before it hits Earth, but you first need to know what it’s made of. Some asteroids are solid rock; some are collections of rubble. The bomb might not deflect it; it might create dozens of smaller pieces.

There’s a big asteroid named Apophis that was once predicted to have a one-in-30 chance of hitting us in April 2029—on Friday the 13th, of all dates. Now the odds are down to about zero, but it could be trouble when it orbits back into our neighborhood in 2036.

So do we try to deflect its orbit? But wait, the calculations might be slightly off and our deflection could actually put it right on track for an impact. Just to make you feel more relaxed, I’ll mention that the Russian space agency already announced plans to deflect Apophis.

Another idea suggests using laser beams to change the temperature of the asteroid’s surface which will, in turn, alter its speed and orbit. Another, the gravity tractor, would position a space craft over the asteroid, with gravity altering the trajectory.

Maybe the money will be found to place a telescope on Venus so we’ll have a better view of what’s out there. That way, even though we won’t know what to do about it, at least we’ll have a much more precise reason to be scared to death.

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