DEFENDING THE PLANET against asteroid strikes. “If you don’t typically follow the debate on planetary defense, you could be forgiven for thinking Earth-crushing asteroids are more the stock in trade of big-budget action filmmakers than an actual concern for the taxpaying American. It might surprise you to learn that John Holdren, director of the White House’s Office for Science and Technology Policy, recently wrote Congressional leaders to recommend that NASA spearhead a multi-agency effort to assess asteroid-deflection technologies.”