The Man Who Guards The Planet

by Jeffrey Kluger,

Space is full of potential killer asteroids. Meet the astronomer who stands between you and them.

Don Yeomans leads JPL’s prosaically named Near Earth Object Program Office, charged with the mission of watching the skies for errant asteroids that are always out there, always moving at dive-bombing speed and always capable–depending on the vagaries of gravity, physics and simple bad luck–of putting Earth in their crosshairs. After decades of being dismissed as apocalyptic nonsense, the threat from incoming space rubble is at last being taken seriously. Funding is up–way up–telescopes and satellites are being assigned to the hunt, and real progress is being made in a cosmic census taking like none before. It’s high time.

The dinosaurs could tell you how a serious asteroid hit turns out–except they can’t because they’re all dead, thanks to a 6-mile asteroid that crashed off the Yucatán Peninsula 65 million years ago, throwing up a globe-cooling shroud of dust and debris that made Earth uninhabitable, at least for them. It’s the same kind of event that flattened 830 sq. mi. of trees across the Tunguska region of Russia in 1908 and the same kind that on the morning of Feb. 15, 2013, clobbered Russia again, this time near the city of Chelyabinsk, injuring 1,600 people and damaging 7,300 buildings.

Someone has to keep an eye on all that cosmic ordnance, and Yeomans, 72, got the job. He is responsible for figuring out ways to deflect rocks that are headed our way.

Yeomans and his team of six other astronomers are currently tracking over 600,000 asteroids, and something new is added to the tote board daily. Every day, we get hit by 100 tons of pebbly debris–all of which incinerates in the atmosphere–including at least one basketball-size object. Every eight months something comes in that’s as big as a small car.

Most of the objects the Near Earth Object (NEO) office is tracking are detected by one of three telescopes, which are in Arizona, New Mexico and Hawaii.

JPL astronomers have now found and plotted the trajectories of nearly 11,000 so-called near Earth asteroids, defined as those that come within 1.3 astronomical units of the sun. A single astronomical unit is the distance from the sun to Earth–93 million miles. So 1.3 AUs means close, but with a 30 million-mile margin of error. To qualify as what’s known as a potentially hazardous asteroid, the object must measure 460 ft. and come within 0.05 AU of Earth–or 4.65 million miles. Currently NASA knows of slightly fewer than 1,500 of these bruisers. The objective is to project orbital cycles at least a century into the future.

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