Volume 2, No. 9                May 28, 1998

An illustrious panel of experts provided testimony at a House Science Subcommittee on Space and Aeronautics hearing (5/21/98) on the perils and opportunities posed by asteroids and comets. Chairman Dana Rohrabacher (R-CA) said the possibility of a large asteroid hitting Earth is "not science fiction" and their detection "deserves much more attention."

Over the next decade, NASA plans to spend about $1 billion on robotic missions to asteroids and comets. Yet the agency is expending only about $3 million a year to detect Near Earth Objects (NEOs) that potentially threaten our planet. Rohrabacher ridiculed NASA for not allocating more resources to address the hazards posed by NEOs, while it can find money for "GoreSat," a $50 million satellite proposed by Vice President Gore to generate a "live" full-size image of Earth for display on the Internet. The California Congressman called the project a "harebrained idea" and quipped that it would allow folks on Earth to watch from space as an asteroid smashed into our planet. Following are highlights of the testimony:

Dr. Clark Chapman, Southwest Research Institute

Only 245 (12 percent) of the 2,000 estimated one-kilometer near Earth asteroids have been discovered to date. According to Chapman, "any one of the other 88 percent -- 1,755 potential killer rocks out there -- could strike at any time, even this afternoon, without warning."

"For every kilometer-sized body," Chapman added, "there are a thousand others capable of 15-megaton impacts like the one that formed Meteor Crater 50,000 years ago or the 15-megaton blast over Tunguska in 1908."

Pilcher emphasized that "NASA is committed to achieving the goal of detecting and cataloging 90 percent of the NEOs larger than one kilometer in diameter within 10 years, and to characterizing a sample of these objects." In FY 1998, NASA doubled funding for NEO programs to $3 million annually. "We are developing and building instruments, and developing partnerships -- particularly with the Air Force -- which should lead to the necessary detection and cataloging capability being in place in one to two years," Pilcher said.

"Rapid, ground-based search for large NEOs is only part of the problem," Canavan warned. "It also is necessary to search for long period comets (LPC)." LPCs swing near Earth at periods greater than 220 years. Canavan said, "Most LPCs have not been observed" and "represent a significant fraction of threat." They "have more stringent detection requirements and require more rapid response." Many LPCs, he offered, "would be observed only on their approach to the Earth." Thus, while decades or even centuries may be available to respond to NEOs headed toward our planet, LPCs "require response times on the order of months to years." According to Canavan, the best way to search for LPCs "as well as other dimmer and smaller objects" is with space-based telescopes.

This November, Earth will experience the largest meteoroid storm since 1966. "Rather than 10 to 15 meteors per hour characteristic of a normal year," Ailor explained, "scientists predict we'll see 200 to 5,000 meteors per hour, and possibly more."

Meteor showers occur when Earth passes through a cloud of debris left behind by a comet. Each November, our planet moves through the remains of comet Temple-Tuttle. "In 1998 and 1999, the Earth is passing very close to the cometäs orbital path at a time when the comet has recently passed by," Ailor said.

"This meteoroid storm will be the largest such threat ever experienced by our critical orbiting satellite constellation," Ailor warned. Most of the comet particles are "smaller than the diameter of a human hair" and will burn up in the atmosphere. Satellites, however, will be "sand blasted" by the particles "traveling more than 100 times faster than a bullet."

In 1966, when the last "meteor storm" (as opposed to a "meteor shower") occurred, there were approximately 150,000 meteors per hour. During this Novemberäs meteor storm, Ailor said "It is possible that some satellites will be damaged, but the most likely source of damage will not be from a rock ‘blasting a holeä in a satellite, but rather from the creation of a plasma, or free electric charge on the spacecraft," which can "cause damage to computers and other sensitive electronic circuits."

The near Earth asteroid Amun, about 2,000 meters in diameter, "contains roughly 30 times as much metal as the entire amount of metals mined and processed over the history of mankind," according to Lewis. "A conservative estimate of the market value of this asteroid is five trillion dollars."

"The large majority of near Earth asteroids," Lewis explained, "contain high concentrations of extremely valuable precious and strategic metals, such as platinum, osmium, iridium, and palladium, and semiconductor components such as germanium, gallium, arsenic, antimony and indium." Additionally, asteroids are rich in water, carbon, nitrogen, sulphides, silicates, and phosphates.

Lewis said the "keys to successful importation of materials from space" are: 1) lower launch costs; 2) selecting targets that are most accessible and have the richest resource concentrations; and, 3) using robotic mining and extraction vehicles.

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