In cosmic terms, we’re insects crawling over a big space rock – and so at times it’s worth pondering whether anybody has called the exterminator. In The Independent, astronomer Chris Impey looks to brighten your day by pointing out the various ways in which the world could end, from asteroid impacts to the end of the Universe itself (and not a restaurant in sight, damnit!). Here’s what he has to say on the Earth as a target in a planetary shooting gallery:
Every century or so, a 10-meter meteor slams into the Earth with the force of a small nuclear device. Tunguska was the site of the last, in 1908, and it was pure luck that that meteor landed in the uninhabited wilderness of Siberia. Every few thousand years, Earth can pass through unusually thick parts of the debris trail of comets, turning the familiar light show of a meteor shower into a deadly firestorm.
Roughly every 100,000 years, a projectile hundreds of meters across unleashes power equal to the world’s nuclear arsenals. The result is devastation over an area the size of England, global tidal waves (if the impact is in the ocean), and enough dust flung into the atmosphere to dim the Sun and kill off vegetation. That could ruin your day. Then there’s the "Big One". About every 100 million years, a rock the size of a small asteroid slams into the Earth, causing global earthquakes, kilometre-high tidal waves, and immediately killing all large land animals. Creatures in the sea soon follow, as trillions of tons of vaporised rock cause drastic cooling and the destruction of the food chain based on photosynthesis. There’s good evidence that this happened 65 million years ago and our tiny mammal ancestors were the beneficiaries as the giant lizards were extinguished.
A hundred million years sounds like a safe buffer, but the next one could happen at any time. But you can take it off your worry list – astronomers have it covered. A network of ground-based telescopes scans the skies for bits of rogue rubble larger than a few hundred meters. That’s ample time to dust off the nuclear arsenals for an interception mission if we had to.
I can’t help but feel that Impey is a little optimistic about our current ability to locate all imminent threats, given how many times recently we’ve only had a day’s notice of some ‘near-Earth’ fly-bys. Not to mention multiple Jupiter impacts over the past two decades, including this one just a fortnight ago (though to be fair, Jupiter’s size and gravity make it the Solar System’s prime impact destination). But I think in the last few years this threat has finally been recognized as a valid one, and the commissioning of facilities like the asteroid hunting Pann-Starrs telescope in Hawaii this week can only be a step in the right direction.
You can find out more about the discovery and tracking of near-Earth objects (NEOs) at NASA’s NEO website.
