Ebay and other Web sites pulse with hundreds of sales pitches. “The pieces below have an exceptional patina,” a site called Star-bits.com said of 10 pictured fragments.

The ads are for chunks of meteorites, bits of asteroids that have fallen from the sky and are as prized by scientists as they are by collectors. As more meteorites have been discovered in recent years, interest in them has flourished and an illegal sales market has boomed — much to the dismay of the people who want to study them and the countries that consider them national treasures.

“It’s a black market,” said Ralph P. Harvey, a geologist at Case Western Reserve University who directs the federal search for meteorites in Antarctica. “It’s as organized as any drug trade and just as illegal.”

The discovery of a rich and historically significant meteorite crater in southern Egypt, just north of the Sudanese border, has shown the voracious appetite for new fragments. Just as scientists appeared to be on the cusp of decrypting the evidence to solve an ancient puzzle, looters plundered the desolate site, and the political chaos in Egypt seems to ensure that the scientists will not be going back anytime soon.