Physicist plans asteroid deflection system

Posted by Emma Woollacott

Lasers could be used to deflect asteroids on potential collision courses with Earth, according to a new study.

The asteroid Apophis - at least 1,100 feet in diameter, 90 stories tall, and weighing around 25 million tons - will make two close passes by Earth at a distance of about 22,600 miles in 2029 and 2036.

And while an impact is unlikely, says  New York City College of Technology associate professor of physics Gregory L Matloff, it could be potentially catastrophic.

But Matloff’s research indicates that an asteroid could be diverted by heating its surface to create a jet stream, which would alter its trajectory, causing it to veer off course.

His team has been working on a solar collector (SC) - a two-sail solar sail configured to perform as a concentrator of sunlight - which over the course of a year could concentrate the sun’s rays on an asteroid, burn off part of the surface and create the jet stream.

To do that, it's necessary to know how deeply the light would need to penetrate the NEO’s surface. "A beam that penetrates too deeply would simply heat an asteroid," explains  Matloff. "But a beam that penetrates just the right amount — perhaps about a tenth of a millimeter — would create a steerable jet and achieve the purpose of deflecting the asteroid."

His team has been experimenting with red and green lasers to see how deeply they penetrate asteroidal rock, using samples from the Allende meteorite that fell in Chihuahua, Mexico in 1969.
 
In a related study, assistant professor of physics Lufeng Leng narrowed the red laser beam and scanned the surface of a thin-section sample, discovering that differences in the depth of transmitted light exist, depending on the composition of the material through which the beam passes.

From their results, they concluded that lasers aimed from a space probe positioned near an NEO could help determine its surface composition. Using that information, solar sail technology could more accurately focus the sun’s rays to penetrate the asteroid’s surface to the proper depth, heating it to the correct degree for generating a jet stream that would re-direct the asteroid.

"For certain types of NEOs, by Newton’s Third Law, the jet stream created would alter the object’s solar orbit, hopefully converting an Earth impact to a near miss," Matloff states. However, he warns, "Before concluding that the SC will work as predicted on an actual NEO, samples from other extraterrestrial sources must be analyzed."

There's something of a debate going on now about what exactly to do about Apophis. The Russians believe that a mission should be scheduled before the first bypass, because gravitational effects from Earth during that initial pass could conceivably alter the asteroid's trajectory.

But the US thinks this is risky: we should be experimenting instead on an asteroid that runs no risk of ever threatening the planet.