“such objects are expected to impact the Earth on average every 2 – 12 years”

A reported meteorite strike in Latvia turned out to be a publicity stunt by a telecommunications company, who are now facing some awkward questions from the Latvian government – BrandRepublic has the video. But, as the Belfast Telegraph noted, there was an unexpected celestial visitor earlier in October – a 5-10m wide asteroid exploded at a height of around 15-20 km over Indonesia on October 8th. Nasa’s Near Earth Object Program reports that the explosion was detected up to 18,000km away and released about as much energy as 50,000 tons of TNT, making it one of the largest asteroid explosions ever observed. There’s an online Indonesian news report with video of the subsequent dust trail. Unlike asteroid 2008 TC3 this one wasn’t spotted in advance. As the NewScientist report points out.

No telescope spotted the asteroid ahead of its impact. That is not surprising, given that only a tiny fraction of asteroids smaller than 100 metres across have been catalogued, says Tim Spahr, director of the Minor Planet Center in Cambridge, Massachusetts. Yet objects as small as 20 or 30 metres across may be capable of doing damage on the ground, he says. “If you want to find the smallest objects you have to build more, larger telescopes,” says Spahr. “A survey that finds all of the 20-metre objects will cost probably multiple billions of dollars.”

Well, our neighbours have seen what can happen. And we can still see the old scars on Earth..