Last week, our planet took two celestial shots. First, a meteor struck Russia, showering the Chelyabinsk region with fragments and injuring several hundred people, and then, Asteroid 2012 DA14 whizzed past. This coincidence of events should be a warning to humanity that meteors are not always as benign as "shooting stars," and that the next asteroid might not miss. Will we heed this warning?
DA14 can be seen as one of about 10,000 near-Earth asteroids that have been discovered in the past 15 years, threatening an impact. Since we have seen these asteroids and are currently tracking them, we can predict any upcoming impacts.
Earth has been hit by one of these relatively small DA14-sized asteroids about once every 300 years, on average. And "small" is far, far from insignificant. The DA14-like asteroid that hit Earth in 1908 did so in a remote region of Siberia, where the explosion (the equivalent of about 250 Hiroshima nuclear bombs going off at one time) destroyed over 800 square miles of the countryside.
Until just about a year ago, DA14 was one of about 1 million similarly sized, near-Earth asteroids, which we know are out there, statistically, but that we haven't yet seen. Until we find them in our telescopes, we are like sitting ducks in a shooting gallery.
Unbeknownst to most people, if we have adequate early warning, our current space technology is sufficiently advanced to deflect these asteroids. For smaller impacts, even a last-minute warning of several days could enable a local evacuation.
Several groups have recommended placing an infrared space telescope into orbit around the sun in order to discover the bulk of Earth-threatening asteroids. The B612 Foundation, a nonprofit organization of former astronauts, scientists, engineers and supporters, is mounting precisely such a mission. This Sentinel telescope is planned for launch in 2018; by the end of its planned lifetime, Sentinel will have discovered well over 90 percent of the asteroids that could destroy entire regions of Earth on impact.
The B612 Foundation has undertaken this project as a nongovernmental initiative. Our motivation is strictly to ensure the survival of life on Earth—all of it.
Rusty Schweickart is a former Apollo 9 astronaut and research scientist living in Sonoma.
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