Fair Warning, Deadly Response
In 2005 the U.S. Congress asked NASA to look into the asteroid threat to Earth, but the agency's report has Near-Earth Object hunters raising more questions.
By Leonard David
As it has in the past, Earth will be on the receiving end of a big bruiser of an asteroid in the future—but exactly when is more a matter of celestial pinball wizardry.
Our planet has the wounds to show just how mean things can get when a near-Earth object (NEO) meets terra firma. As example, take your own flyby of that hole in the desert created some 20,000 to 50,000 years ago in a tourist spot now dubbed Arizona's Meteor Craters near Winslow.
Another case in point is next year's celebration of the 100th anniversary of the Siberia-smacking Tunguska event of a 150 to 170 feet (45 to 50 meter) diameter NEO. Had it struck just a few hours later, London or Moscow might have felt the wrath of this cosmic interloper. Instead, it cleared out 800 square miles (1,300 square kilometers) of Siberian forest—maybe taking out a few reindeer in the process.
But NEO history lessons are one thing. You should keep an eye to the sky in 2029 as the asteroid Apophis sails by Earth, zipping closer to us than where geosynchronous satellites reside. There's a slim but still real chance that the space rock could hit Earth on its return pass in 2036.
While the NEO threat is small, it is not zero. Such a real risk deserves real action planning. Over the years, there has been no shortage of ideas on how to fend off unfriendly fire from the cosmos, be they utilizing laser beams, space tugboats or solar sails, or even using powerful anti-NEO bomb blasts, conventional explosives as well as nuclear.
Last year NASA began a congressionally mandated, fact-finding appraisal of how best to detect, track, catalog and characterize near-Earth asteroids and comets. Furthermore, U.S. lawmakers asked the civilian space agency to identify what could be done to deflect an object found on course to strike our planet.
Back in late June 2006, leading experts from a variety of fields met in Vail, Colorado, brought together under the banner of the NASA workshop Near-Earth Object Detection, Characterization and Threat Mitigation. The meeting was a unique, idea-gathering event—meant to provide lawmakers with an executable program. Congress had asked NASA, in part, to use its "unique competence" to deal with the potential hazard faced by Earth from NEOs and help establish a warning and mitigation strategy.
Last March the NASA report titled "Near-Earth Object Survey and Deflection Analysis of Alternatives"—a 27-page data dump taken from a more than 270-page evaluation—landed upon the desks of lawmakers.
One key suggestion from the report was a way to divert a potentially hazardous object—labeled PHO: namely, that nuclear standoff explosions were 10 to 100 times more effective than the non-nuclear alternatives analyzed. Non-nuclear kinetic impactors, the report noted, are the most mature approach and could be used in some deflection/mitigation scenarios, especially for NEOs that consist of a single small, solid body.
Wrong, Wrong, Wrong
One early responder to the report is not too pleased, calling the document replete with errors of both omission and commission.
"NASA did a terrible technical analysis," complained Russell "Rusty" Schweickart, a former Apollo astronaut. "It's wrong, wrong, wrong," he told attendees of this year's International Space Development Conference (ISDC) meeting in Dallas.
Schweickart is chairman of the B612 Foundation board of directors, a confab of scientists, technologists, astronomers, astronauts and other specialists dedicated to significantly altering the orbit of an asteroid in a controlled manner by 2015.
"Right now, I put NASA in the same category of technical accuracy as Hollywood with Deep Impact and Armageddon," Schweickart noted, referring to those two less-than-factual movies about dealing with NEOs on a deadly course with Earth. "The report as it stands is not valid. The recommendations that they made are based on an exceptional set of asteroids that they picked rather than what is most likely to be needed to be deflected," Schweickart said. "It's a flawed report."
Taking a pro-nuke approach is wrongheaded, Schweickart said at the ISDC. Rather, using existing robot impactor technology as well as a gravity-tractor method of altering the asteroid's trajectory ever so slightly would give you both the oomph and the precision that you need to redirect an NEO from an impact with Earth.
"In terms of responding to Congress regarding what possible alternatives there are, NASA picked ridiculously improbable events...and you end up with something incredibly big, like a nuclear blast. That's not a reasonable answer. When you are looking at a supply of something, you've got to first look at the demand to say what's required. And if you look at the demand side, the most likely things to happen are much smaller than that...and that's not a way to answer responsibly to Congress, in my view," Schweickart told Ad Astra.
Another Schweickart gripe about the NASA NEO study is that the space agency's analysis makes the assumption that deflecting an approaching NEO consists only of causing it to miss the planet at the time of the nominal impact. The analysis does not account for the fact that there are hundreds of resonant return points and associated impact "keyholes" located along the path of deflection. If a deflection fails to account for these keyholes, the NEO may miss the Earth at the time of impact only to return in a year or two for another impact. NASA's analysis assumes that the stronger the deflection, the better.
Schweickart and planetary scientist Clark Chapman have separately reviewed NASA's NEO report and have provided their technical critiques to NASA, going as far as appealing to NASA Administrator Mike Griffin to review and revise the report to Congress correcting technical errors and rethinking the study's recommendations and conclusions.
Meanwhile, Donald Yeomans, manager of the NASA Near Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California, said that, in his mind, the report has been unfairly treated by some members of the community.
Congress asked the agency to analyze possible alternatives that NASA could employ to divert an object that is on a probable collision course with Earth, Yeomans pointed out. The analysis, he added, found that some deflection techniques require far less advance knowledge of the object's physical characteristics than others. "For a relatively large threatening object for which there was little warning time, stand-off nuclear blasts might be the only viable option since this technique, as controversial as it may be, is relatively insensitive to the object's density and rotation characteristics and can impart significant energy for the deflection. But clearly, this option would only be used when necessary."
Yeomans advised that the analysis does not preselect or prefer any particular option and shows that a number of the analyzed options could be appropriate in some scenarios. Furthermore, the report does not recommend any particular deflection options, he said, and the analysis of alternatives only provides guidelines for initial discussions of which options may be appropriate.
On June 18 there was a high-level meeting on the NEO report to Congress, held at the space agency's Office of Program Analysis and Evaluation at NASA headquarters, in Washington, D.C.
Chapman rated the NASA meeting as a "sad day" for those hoping to move constructively toward systematic thought on how best to deal with the potential hazard of a dangerous space rock smacking into Earth. "From my perspective, the meeting was very disappointing," he said, adding in a post-meeting report: "I think it is a shame that the American space agency, looked upon for its expertise around the world, should treat this global issue in such a shoddy fashion."
Indeed, despite the current debate over the NASA report, how best to deal with NEOs should be a worldwide worry. In any dealings with space rocks, there is need for early warning, a deflection capability and an international decision-making capability. And in this regard, Schweickart wears another hat as chairman of the Association of Space Explorer's (ASE) Committee on Near Earth Objects. Through the ASE organization a set of international workshops, stretching over a year and a half, are being held to further detail the NEO threat and promote a global response to potential Earth-threatening objects. The results of these workshops are to be submitted in the spring of 2009 to the U.N. Committee on the Peaceful Uses of Outer Space.
Schweickart tags the NEO issue a "cosmic natural hazard"—one that nobody is currently responsible for in terms of handling the threat, be they within the U.S. government or any other government. In the next 15 years, the population of the world is going to be concerned about this issue, he predicts, and urges that "Mission Rules" for NEO deflection be drawn up by the international community.
"If we do our homework right, never again should an asteroid that can do damage on the ground impact the Earth," Schweickart stresses. "We're living at a time—with our technology—we have the capability to eliminate this major shaper of evolution...the evolution of life on this planet."