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Only nukes can stop planetsmash asteroids, say US boffins

Nix on the 'world free of nuclear weapons', Mr President

Top American boffins have warned that the US government's efforts to prevent global apocalypse caused by meteor strike are inadequate. The scientists add that nuclear weapons are the only practical means of defence against large, planet-wrecker sized asteroids.

In a new report, the US National Research Council says that so-called Near Earth Objects (NEOs) fall broadly speaking into three classes.

First and most terrible are large NEOs bigger than 1km (eg roughly Vatican sized and up) which would release energies in the hundred-thousand-megaton range - more than a global nuclear war, and with similarly catastrophic consequences for human civilisation or even survival. NASA has got most of these NEOs logged in its databanks, but not all - there are likely to be a few on orbits which only bring them within observation at very long intervals.

Apart from planet-busting big jobs like these, however, there are also a lot of quite hefty space boulders, snowballs etc in the 140m+/cathedral size range. These, owing to their terrific speed, would tend to cause destruction in the hundred-megaton range on impact - equivalent to a limited nuclear bombardment.

NASA was ordered by the US Congress to log 90 per cent of these medium-sized NEOs by 2020, and according to the National Research Council analysts this simply isn't going to happen as things stand - in large part because the politicians didn't assign any extra funds and the administration has asked for none. The $4m per annum the US currently spends on sky-search activities is seen as inadequate.

That said, the NRC's new report offers some alternative ways ahead which could see most of the threatening space objects spotted - either on time by 2020 using an expensive space-based telescope system, or taking a bit longer using cheaper ground instruments. The boffins also say that NASA should start scanning for smaller, 30-50m (ordinary church) sized objects, as these would still be very nasty if they hit in a populated area.

This much had already been mostly stated in a preliminary report released last year, but the NRC boffins have now gone further and taken a look at the various tactics humanity might use in the event of a dangerous NEO being detected. There are many of these, some of them quite delicate and refined - using the gravitational pull of a spacecraft's own mass to minutely drag an asteroid off course, for instance.

But "slow push/pull" methods like these are practical, according to the NRC, only for smaller NEOs and "would likely require decades of warning". Even "kinetic" plans where a spacecraft crashes into an asteroid would only work on less potent sub-Vatican threats, and again "may require decades of warning".

In the current state of human technology, the NRC warns, the only way to be sure is to nuke 'em from orbit:

Nuclear explosions are the only current, practical means for dealing with large NEOs (diameters greater than 1 kilometer) or as a backup for smaller ones if other methods were to fail.

It would seem that current plans by President Obama to strive for "a world free of nuclear weapons" would in the end - sooner or later - be a death warrant for humanity, rather than its salvation.

The full NRC report can be read here. ®

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