THE sight of the solar system's biggest planet being battered by the broken remains of a comet in 1994 left a vivid reminder of our own planet's vulnerability. The scars that remained after the series of giant impacts on Jupiter were more prominent even than its great red spot, and remained visible for months.
This dramatic spectacle was enough to loosen government purse strings, and the funding has supported telescope surveys to hunt down asteroids that could wallop us. A decade and a half after comet Shoemaker-Levy 9 smashed into Jupiter, those surveys have catalogued more than 80 per cent of the near-Earth asteroids larger than 1 kilometre across.
Now we have seen the results of the first exercise ever to test plans for what to do if an asteroid is on collision course with Earth (see Asteroid attack: Putting Earth's defences to the test), and they do not inspire confidence. We still have a long way to go before we can say we are prepared for this cosmic threat.
Improved early-warning capabilities are one cost-effective solution.
There are telescopes on the drawing board that could find objects as small as 140 metres in diameter. That's a big advance on what we can do now, even if objects 30 to 50 metres across are more numerous and therefore arguably more dangerous.