When planetary scientist H. Jay Melosh attended a meeting between nuclear weapons designers from the United States and the former Soviet Union in May 1995, he was surprised by how eagerly the ex-Cold Warriors sought to work together against an unlikely but dangerous extraterrestrial threat: asteroids on a collision course with Earth.
"It was a really bizarre thing to see that these weapons designers were willing to work together-to build the biggest bombs ever," said Melosh, a geophysicist at Purdue University and expert in space impacts who has an asteroid named after him.
Ever since, he
has been pushing back against relying on nuclear bombs for the Earth's defense, arguing that a non-nuclear solution-diverting the trajectory of asteroids by hitting them with battering rams - is both possible and much less dangerous.
Melosh said Dearborn "is reasonable, he tends to be pretty persuasive, he comes across as not being a rabid advocate of nuclear weapons for their own sake.
and Dearborn disagree, with Melosh asserting that since no large, Earth-killing, near-term threats are on the horizon, "the remaining smaller objects can be dealt with by non-nuclear means, kinetic detection being the most straightforward" and technically advanced.
"I think that the need for deflecting very large objects that might require nuclear detonations is waning and that a reevaluation of realistic needs is very much in order," Melosh
But the report also supported Melosh's
approach, ramming an asteroid with a heavy object.
Melosh also served on the National Research Council panel, but says he disagreed with some of the report's conclusions.
was the co-investigator on a 2005 NASA mission known as Deep Impact that launched an 820-pound copper-covered battering ram that gouged a crater out of the comet Tempel 1 in 2005, and measured its effect.
says the same basic approach could be used with asteroids that threaten Earth.
says the nuclear option would not work with existing weapons, but only with new, even larger nuclear explosives than exist in any arsenal.
said panelists were limited under the terms of the National Research Council study to suggesting approaches that could be used in the next twenty years - giving the nuclear option an advantage, because a stockpile of weapons is already available.
"I think in the long term there are much more effective efforts," he
Whatever the solution, Melosh
says, the human race has the time to pursue safer alternatives.
"A lot more people have been recorded to have died from nuclear weapons than have been recorded to have died from asteroid impacts," he