Wednesday, April 20, 2005

Too close for comfort

We can all rest easy - Asteroid 2004 MN4 probably won't hit the Earth on Friday, APril 13th, 2029. Instead it will miss us by 20,000 - 40,000 kilometres. But that's still far too close for comfort - only four to seven earth radii - and anything which passes inside the orbit of the moon is a real worry. Worse, it will be back for another shot - and the influence of the Earth's gravity makes it unpredictable exactly where it will go. So as early as 2034, somewhere could be getting 1000 Megatonnes of rock dropped on it...

What can we do? A first step would be to tag the asteroid with a transponder, so we know where in the hell it is. The data from this could be used to refine its orbit, and make a more accurate prediction of where and when it might hit. We also need to start thinking about how to move this cosmic traffic hazard somewhere safer - ideally before its too late. And we need to start finding other similar objects. We didn't notice this one until last year, when it seemed to be on a direct collision course; what if there's another one out there?

If we don't start doing this, then one morning we're going to wake up and find that Venice or New York or where-ever has been vaporised, or that San Francisco and Tokyo have been drowned by an asteroid-induced tidal wave. And while that's not the end of the world, it's certainly unpleasant enough to justify further action.


I'm not sure how a transponder would help - it'd be quite difficult to place - getting a spacecraft to rendezvous with the thing is one issue, as is how you'd attach the transponder to a gravityless asteroid, and ensure it was pointed in our direction.

It might be easier to have a better, possibly space-based, radar.

How are we going to move it anyway - you can't really send Bruce Willis you know? If you nuke it then you may just get lots of bits of rock flying around.

One way I've seen suggested would be some kind of solar sail to alter an asteroids orbit.

Posted by Rich : 4/20/2005 11:28:00 AM

A large spike, possibly. As for the right direction, use a unidirectional beacon, and hope its not screened by rock most of the time.

Radar is because of the physics involved - its suffers from the inverse-square problem twice (once to get the signal there, and once when it is bouncing back); with a beacon we only have to worry about it once.

As for moving the thing, you can try a nearby nuclear explosion to cause outgassing - but a solar sail might be less dangerous. We need good orbit data before we can do either, though - otherwise we might just be pushing it into ourselves.

Posted by Idiot/Savant : 4/20/2005 11:45:00 AM

Neh. Its less dangerous than lake Taupo, or any of about a dozen other active caldera volcanoes, or another 8 to 9 magnitude earthquake on the various pacific rim subduction zones.


Posted by Anonymous : 4/20/2005 12:02:00 PM

I wonder how much effort it would take to bring it into orbit and mine it. Depending on its composition it could be a valuable resource.

Posted by Anonymous : 4/20/2005 12:29:00 PM

Bill Bryson points out in A Brief History of Everything.. there's are plenty of rocks out there that are 99.9% dark, ie practically invisible to us, moving at speeds such that time from entering atmosphere to hitting earth is about 2 seconds..

Maybe the answer is to cozy up to your personal choice of deity ignore the rocks - science is pretty omnipotent in the face of them.

Posted by Anonymous : 4/20/2005 01:57:00 PM

Push it out of the orbital plane (ie. "South" in space). It will slingshot out of the solar system, and out into some other solar system. We could also accelerate it's orbit and watch it crash into Jupiter on the other side of the solar system.

If Earth's space agencies try to move it, it will likely be with the new Ion Engines they've been developing. They're cheaper than fuelled rockets, and they're more reliable than solar sails.

Posted by Geoff : 4/21/2005 04:25:00 PM