Apocalypse averted: How NASA's Don Yeomans watches the sky for Near-Earth Objects

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First aired on Quirks & Quarks (12/01/12)

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Although from way down here on Earth outer space appears to be mostly empty, there's actually lots of stuff moving very fast way out there in the void. So if you run into something hurtling through space, it's probably going to be a fairly dramatic event -- just ask the dinosaurs. Don Yeomans has made a career out of studying things that hurtle through space, like asteroids and comets -- things that might someday hurtle our way, creating a situation straight out of the movie Armageddon.

Yeomans is a senior scientist at the Jet Propulsion Lab and the manager of NASA's Near-Earth Object Program Office. His job is to keep his eyes open for any apocalypse-inducing flying objects that might be on a trajectory heading towards Earth. And last week he spoke with Quirks host Bob McDonald about his ominously titled new book, Near-Earth Objects: Finding Them Before They Find Us.

According to Yeomans, this type of skywatching is relatively new. "Until about 20 years ago, people simply weren't looking for these objects. They're relatively small and relatively dark and they're hard to find, despite the fact that they've been zipping by the Earth for billions of years," he said. "But it was only in the past 20 years that people have started paying attention, particularly NASA."

The sky is full of all sorts of detritus, but what Yeomans defines as "near-Earth objects" is specific to comets ("rocky bodies with ices") and asteroids that are on orbits that come within 30 million miles of Earth's orbit. Yeomans says that the most dangerous asteroids are the ones that are on a similar trajectory to the Earth. "They orbit the sun at approximately one year intervals, and they can get very close to the Earth because they cross the Earth's orbit," he explained. "The ones that could cause extinction events that are a kilometre [across] or larger...we think there's about a thousand of those. But we've found about 900 and none of them represent a threat."

So can we rest easy? Not necessarily. Smaller asteroids and comets can cause damage too. "As they get smaller and smaller there are more and more of them," said Yeomans. A near-Earth object of about 40 metres could still do considerable damage, and there are potentially millions of those out there. "[A near-Earth object of] 40 metres or larger could actually punch through the Earth's atmosphere and cause an airblast that would cause significant damage on the ground."

In 1908, one did hit in Russian Siberia. "Fortunately, that wasn't a populated area, but it did wipe out trees in a 27-square-mile area, and cause severe burning events in the area, and knocked a gentleman off his chair some 20 kilometres away," Yeomans said. "So should an object like that hit over an inhabited city it would be catastrophic."

And we can all rest a little easier know that Yeomans is watching the skies for us.

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