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Preparing for Possible Killer Asteroid

By John Fleck
Journal Staff Writer
          If we ever need to use Los Alamos scientist Cathy Plesko's research, we're in nail-biting trouble. But at that moment we're likely to be very glad she did it.
        Plesko is trying to figure out how to deflect an asteroid on a collision course with Earth.
        "You hope you never need it, but you know, you hope you never need car insurance," said the 29-year-old researcher.
        Plesko uses the massive supercomputers at Los Alamos National Laboratory to simulate what would happen if we used nuclear weapons in deep space to nudge a threatening asteroid, deflecting it onto a new course so it misses Earth.
        Plesko acknowledges we are years away from knowing enough to pull it off. How big a blast is needed? Would we have to use more than one?
        But she is among a growing group of scientists who believe it is important to do the work now, before a threat emerges, so we have the tools in hand to deal with the situation if — when? — we spot the Big One headed our way.
        In a January report, a federally chartered National Research Council panel concluded that, given the small but very real risk of a planet-altering collision, we should be doing more to track killer asteroids and prepare a response should a threat be discovered.
        For now, the closest thing to a Big One out there that we know about is an asteroid named Apophis, which NASA scientists estimate has a one-in-250,000 chance of hitting Earth on April 13, 2036.
        An estimated 1,000 feet in diameter, Apophis would be big enough to destroy a country the size of Costa Rica, and maybe its neighbors, if it actually hit, according to Mark Boslough, a Sandia National Laboratories scientist who was a member of the National Research Council asteroid panel.
        Costa Rica is not a random choice. While the odds are against an impact, scientists have been able to calculate a "what if" scenario for the remote possibility of an impact. Costa Rica lies right in the middle of that possible Apophis impact path, along with Russia and vast stretches of ocean.
        Given the astronomically small odds that Apophis will hit Earth, it is mostly an intellectual curiosity at this point. The problem, according to the National Research Council panel's report, is that there likely are a lot more Apophis-sized asteroids out there that we don't know about.
        In 2005, Congress directed NASA to establish an asteroid survey aimed at finding the vast majority of the potentially threatening asteroids down to about half Apophis's size by 2020. But, according to the National Research Council report, funding for the surveys has lagged, and current efforts will not meet that goal.
        Funding for technologies to protect Earth once we find a killer asteroid lags even further. But a determined band of researchers like Plesko is plugging away at the problem.
        One idea being considered by scientists is the use of a nuclear blast to nudge an asteroid, changing its orbit so it misses Earth. If we had a decade or more of lead time, which is not out of the question, a small nudge would probably do it.
        But understanding in detail the effect of such a blast is a hard problem, Plesko said.
        In their most recent project, Plesko and her colleagues studied the effect of a nuclear explosion on a "rubble pile" asteroid — a common type of asteroid that is made up of a smaller rocks all bound together in a ball by the force of their own gravitational attraction. (Most of the asteroids that could threaten Earth are really gravitationally bound rubble piles, rather than big, solid rocks.)
        Their calculations showed that the blast would blow apart the rubble pile, but that the individual rocks' gravitational attraction would pull them back together in less than a day.
        When Plesko presented her results at a scientific meeting last month, some in the audience concluded the fact that the rubble pile ended up much as it was before the blast meant such a blast would be a failure. But that misses the point, Plesko said in an interview. The nudge from the nuke could nevertheless have changed the asteroid's path, she said.
        We're a long way from knowing enough about the problem to actually deflect an asteroid, Plesko said. But the research raises interesting questions about how society might go about using information developed by scientists like Plesko to make bet-the-planet decisions.
        On the surface, it looks like a simple problem — get the scientists' best advice, then act on it. But cases where we end up arguing about what really counts as their "best advice" are legion, from nuclear waste disposal to genetically modified foods to climate change.
        No matter how precise the calculations, there will be uncertainties attached. Rather than deflecting Apophis completely, would the nudge merely shift its path so it hits in the mid-Pacific, saving Costa Rica but creating a towering tsunami that destroys coastal California?
        Dan Sarewitz, an Arizona State University researcher who studies what happens at the interface of science and societal decision-making, thinks the asteroid problem would be easier to act on than something like climate change or nuclear waste disposal.
        If and when we discover an asteroid actually headed toward Earth, "There will be very little argument about whether that's a serious problem," Sarewitz said.
        Nukes are just one of the asteroid deflection strategies on the drawing board, and Plesko and her colleagues are working hard to reduce the uncertainties associated with their use, in terms of the amount of nudge a warhead would actually impart to the speeding asteroid.
        "This is really very much in its infancy," she said of the research.
        UpFront is a daily front-page opinion column. John Fleck can be reached at 823-3916 or jfleck@abqjournal.com.

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