Wednesday night

So where did it come down? People in the San Francisco Bay area are still puzzling over the fireball that went shooting across the sky Wednesday evening, making an audible boom and, perhaps, spreading debris across the suburbs and vineyards north of the city.

Scientists said the object was a meteor, most likely an errant hunk of rock from the asteroid belt between Mars and Jupiter, traveling in an orbit that happened to send it tearing into the atmosphere over California.

Astronomers have been trying to calculate its trajectory from eyewitness reports, and there's been natural disagreement over where any meteorites - fragments of a meteor that survive entry into the atmosphere and reach Earth's surface - might have come down. Bill Cooke of NASA's Meteoroid Environment Office in Alabama said he thought most debris would have ended up out in the Pacific. Peter Jenniskens of the SETI Institute, a meteor hunter by background, suggested debris may have crashed near California suburbs such as Novato or Martinez.

But in a case like this, calculations only do you so much good. If you're interested in meteorites, there is only one thing to do - go out and look for them.

So Jenniskens, according to his office, was out in the field today, looking for shards of rock that, to the trained eye, would likely have been survivors of a trip from space. They may just be pebbles, or they may be larger than your fist, but they're often smoothed and rounded by friction with the atmosphere.

Jenniskens' office said he would be organizing people who came on their own to look. One person, asking not to be quoted since meteorites are Jenniskens' subject, said this is a delicate issue. Fresh meteorites are rare - so they have a market value. This person said that Jenniskens, searching in the name of science, may find himself in a race against other meteorite hunters who see the potential for profit.