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You may have heard that there is an 86 per cent chance that in a mere million years or so Gliese 710 will drift close enough to the solar system to perturb the Oort cloud and perhaps send a rain of comets down into the inner solar system.

Also, you have probably heard that there are hints of a certain periodicity in mass extinction events, perhaps linked to the solar system moving through the denser parts of the galactic disk, increasing the probability of similar close encounters.

So, the big bad is coming… sometime. It might just be a stray asteroid that’s in the wrong place at the wrong time and have little to do with what’s happening outside the solar system. In any case, we need to stay calm and carry on – and maybe print the following handy survival tips on a fridge magnet.

Immediate action: Fund sky surveys.

The Spaceguard Survey is underway aiming to identify near Earth objects down to the size of 140 meters. At present the survey might be finished in ten or fifteen years and it completely missed two small objects which are thought to have hit Earth in 2002 with impact energies approaching half a kiloton.

Uh, anyone think we could be doing more in this space?

Medium term action (0 – 10 years): Evacuate the area

The 2010 National Academy of Science (NAS) report uses the strange term civil defence, but really it just means run for your life (i.e. evacuate the anticipated impact site). City destroyers in the 140 meter plus range may only hit Earth every 30,000 years or so, but it doesn’t hurt to be ready.

Mass extinction objects in the ten kilometer range may only come every 65 million years or so. If it’s one of these… bummer.

Long-term action (10 years plus): Call Roger Ramjet

If we do have around 10 years notice, there’s maybe enough time to launch some of the nifty technology solutions we have at least developed on paper. Gravity tugs and mirror bees and various other deflection devices are recommended to deflect objects threatening to pass through a gravitational keyhole and shift onto a collision course next time around.

If the object is already on collision course, no-one’s ruling out ‘instantaneous force’ (IF) options, which are either crashing something into it (‘kinetic impact’) or just nuking it – although the NAS report notes a 500% uncertainty about the possible trajectory change resulting from an IF. Ideally, a ‘full deflection campaign’ involves an IF primary deflection followed by subsequent shepherding of one or more fragments onto a safer trajectory via your preferred deflection device.

And look, if it does all goes bad at least the next order of intelligent Earthlings might dig up all these fridge magnets with mysterious symbols printed on them and be able to figure out where we went wrong. My money is on the birds.

Recommended reading:

The Association of Space Explorers’ International Panel (chaired by Russell ‘Rusty’ Schweickart) report. Asteroid Threats: A Call For Global Response.

National Research Council report. Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies. Final Report.