MOUNTAIN VIEW (CBS SF/AP) – An event similar to the meteor explosion in the sky over Russia Friday morning, which blasted out countless windows and injured as many as 1,000 people, could happen without much warning in California, according to a local space scientist.

Seth Shostak, a senior astronomer at the SETI Institute in Mountain View, wasn’t entirely surprised by what happened, considering there are 40,000 to 50,000 small space rocks in the solar system that have yet to be, as the experts say, “categorized.”

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“Because we haven’t yet mapped them they come in sort of, if you will, unexpectedly,” Shostak explained. “They’re coming in through the back door and you only know about them when they finally hit the atmosphere, by which time of course it’s entirely too late to think about doing anything about them.”

Predictable incident or not, Shostak was up early and watching news coverage of the incident closely.

The Russian Academy of Sciences said the meteor entered the Earth’s atmosphere going at least 54,000 kph (33,000 mph). It shattered about 30-50 kilometers (18-32 miles) above the ground, releasing several kilotons of energy above the Ural Mountains.

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“Given the density of these things, it’s on the order of the size of a truck or a bus or something like that. It’s relatively small, maybe as big as a small house,” said Shostak.

Amateur video, broadcast on Russian television, showed an object speeding across the sky just after sunrise, leaving a thick white contrail and an intense flash.

The obvious question on the ground was can or will it happen again?

“There are tens of thousands of those,” pointed out Shostak. “It’s going to take a long while to catalog them all, and even if you do that, it’ll be hard to avoid the occasional hit from these small visitors from space.”

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