60-Second Space

Shoo Away Asteroids with a Coat of Paint

Heat radiating from an asteroid imparts a tiny push to the rock, meaning that we could subtly steer an asteroid by changing its reflectance. John Matson reports

Since that meteor streaked through Russian skies on February 15th a lot of people have been thinking about asteroid defense.

If an inbound space rock were discovered early enough, a spacecraft could divert it any number of ways: by nuking it, smashing into it or tugging it off course. Then there’s an idea advocated by aerospace engineer David Hyland of Texas A&M University: just spray a coat of paint on the asteroid and let the sun do the rest.

The proposal relies on the so-called Yarkovsky effect. The hottest part of an asteroid—where it’s afternoon, asteroid local time—radiates the most heat into space, and those thermal photons impart a gentle recoil force. It’s incredibly subtle, but it’s constant, so the Yarkovsky effect can significantly change an asteroid’s orbit over time.

A new study in the journal Icarus identifies more than 20 asteroids that have been noticeably shifted by the Yarkovsky effect, naturally. [Davide Farnocchia et al., Near-Earth Asteroids with measurable Yarkovsky effect] Paint would enhance or reduce the effect by changing an inbound asteroid’s reflectance, thereby steering it away from us.

Currently no asteroids that we know of present a real threat to Earth. But it’s good to be prepared. Ask the dinosaurs.

—John Matson

[The above text is a transcript of this podcast.]

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