Will Nuclear Megaton Shockwave Avert Earth-bound Asteroid?

From: http://www.iwatchnews.org/2012/03/14/8394/looking-interplanetary-defense-work

Looking for interplanetary defense work?

A quick take on Earth's defense system against asteroids, and a possible contractor for the job

By R. Jeffrey Smith

2:30 pm, March 14, 2012 Updated: 2:31 pm, March 14, 2012

We were shocked to read on Discover magazine’s website last week that an asteroid 450 feet across, lurking just now on the other side of the sun, stands a (remote) chance of smacking us — or someone else on earth — in about 29 years. Scientists presently judge the probability to be around 1 in 625, which seems like a substantial upgrade from the usual estimate of a one in 5,000 chance that a major asteroid will hit Earth in the next century.

More will be known next year, after new calculations, and everything hinges on the asteroid — with the mild name of AG5 — passing through what astronomers are calling a space “keyhole” that could bend its orbit toward earth sometime in 2023. So there will be some time to prepare. But frankly we can see the opportunity for some defense industry contracts right now, and it’s not hard to pick out a front-runner.

With uncanny foresight, some scientists from Los Alamos National Laboratory prepared a video that was uploaded to YouTube in the middle of last month extolling how their newest Cray supercomputer can model the impact of an “energy source” on an asteroid. Robert P. Weaver, identified only as an R&D scientist at the New Mexico lab, narrates how the shock wave from a one-megaton-sized explosion — he never mentions the “n” word, for the nuclear weapons at the heart of the lab’s work — would blast a much larger asteroid into smaller bits of rock.

There’s no discussion about the consequences of creating so much debris in space, where the clutter is already threatening satellites and the space station. But it’s good to know we might not be defenseless. NASA has actually studied what’s engagingly called “planetary defense,” but so far it has deflected, so to speak, a call from former astronaut Rusty Schweickart to begin a special study of the threat of attack by the rock known as AG5.

From: http://planetary.org/about/press/releases/2012/0315_Asteroid_2012_DA14_Discovery_Enabled_by.html
CONTACT:
Mat Kaplan
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E-mail: mat.kaplan@planetary.org

Asteroid Will Pass Closer To Earth Than Many Satellites--
Discovery Enabled by Planetary Society Grant

In less than a year, an asteroid that is half the size of a football field will pass within just a few thousand miles of our planet. The discovery of this object, dubbed 2012 DA14, was made possible by a Shoemaker Near Earth Object (NEO) grant provided by the Planetary Society.

Click to enlarge > Processing method to reveal fast-moving asteroids Credit: Courtesy Jaime Nomen, La Sagra

The giant space rock was discovered on February 22, 2012 by La Sagra Observatory in southern Spain. One of the observatory's telescopes had recently been upgraded through the Planetary Society grant. Its new camera enabled detection of fast moving objects like 2012 DA14 – requiring very fast imaging for discovery and determination of their paths. The upgraded instrument has far outperformed the Observatory's other telescopes. It has found more than ten NEOs, along with a previously unknown comet.


At fifty meters across, 2012 DA14 is similar in size to the object that caused the Tunguska air burst over Siberia in 1908, leveling 2,000 square kilometers of forest. Fortunately, there is no danger of impact during the next pass of 2012 DA14.


“This asteroid is a wakeup call for the importance of defending the Earth from future asteroid impacts,” says Bill Nye, Chief Executive Officer of The Planetary Society. “Big impacts don’t happen often, but they will happen.”


2012 DA14 will come closest to Earth on February 15, 2013. It will zoom to within about 3.5 Earth radii or about 22,500 km from the Earth’s surface, well within the orbit of geostationary communications satellites (35,800 km). Current estimates are that it will be about magnitude 7 in brightness – not quite visible to the naked eye, but within reach of binoculars or a small telescope. It will fly across the sky at about one Moon diameter per minute.


Additional follow-up by observers around the world has resulted in this accurate prediction of the asteroid's current orbit by scientists at the Jet Propulsion Laboratory's Near Earth Object Program Office. Knowing the close approach is coming will allow astronomers to study the characteristics of the asteroid. A major goal will be greater refinement of its orbit so that future close approaches and even possible impacts can be predicted and prepared for.


Jaime Nomen and his colleagues at La Sagra Observatory have introduced observing strategies designed to improve the probability of discovering asteroids that larger surveys may miss. Nomen reports, “We try to find smaller objects located close to Earth that generally move at high angular speed. They may appear anywhere in the sky, even if that sky region had already been thoroughly searched just days before.”


The strategy paid off. With the new CCD telescope camera configured to shoot rapid, short exposures, Nomen and his colleagues captured 2012 DA14 as it moved across the sky at almost 11 arcseconds per minute. This is slower than a satellite but quite fast for a NEO. It's equivalent to a lunar diameter every three hours. The asteroid was already heading away from Earth after passing the planet about a week before, and at much greater distance than next year's encounter. Its path across the eastern sky, fast angular motion, quite faint (and fading) brightness, and high declination (far above the ecliptic plane in which most of the planets travel) could easily have allowed 2012 DA14 to escape undetected.


Planetary Society Gene Shoemaker grants are awarded to amateur observers, observers in developing countries, and professional astronomers who, with seed funding, can greatly increase their programs' contributions to NEO research. The program, begun in 1997, is named for Gene Shoemaker, a highly respected leader in the study of impact structures, and an advocate for NEO discovery and tracking programs.


The Planetary Society supports several projects that are helping to find near Earth objects and test techniques that may allow humanity to deflect a NEO that is headed toward a potentially catastrophic impact. The Society is committed to planetary defense. "Discovery, follow-up, and characterization of asteroids enabled by our Shoemaker grants is one of our most gratifying rewards,” says Bruce Betts, the organization's Director of Projects. “We want to help humanity avoid the world’s only preventable natural disaster. Astronomers like those at La Sagra Observatory are critical to that goal. Their discovery and next year's close approach will result in a scientific and planetary defense treasure trove of data.”


The 2012 DA14 flyby in 2013 will also serve as a warm-up for a similar fly by in 2029 by the much larger Apophis, a 270-meter asteroid co-discovered by Shoemaker NEO grant winner Roy Tucker.


For more information, including an update on the discovery and follow-up from Jaime Nomen of La Sagra Observatory, visit http://planetary.org/programs/projects/neo_grants/