The balloon climbed to a height of over 30,000 metres (100,000 ft). It carried a Webcam so that Net users could follow the experiment as it happened.

The dust particles, or meteoroids, are typically no more than a few thousands of a millimetre across. They enter the Earth's atmosphere at high speed and burn up, leaving a trail of light most people will know as shooting stars.

Researchers, from Nasa's Marshall Space Flight Center, are keen to know more about these extremely small pieces of dust.

Comet debris

They conducted a similar experiment last November during the Leonid meteor shower, a regular astronomical event which occurs when the Earth passes through the debris left in space by Comet Tempel-Tuttle.

A Leonid fireball in the Hong Kong sky

Saturday's flight was intended to help the scientists better understand the data they gathered at the end of last year.

"It's a simple control experiment," says John Horack from the Marshall Space Flight Center.

"We've flown one balloon when the meteoroid flux at the very top of the atmosphere was high, and now we're going to fly another when the expected flux is low."

Chemical composition

The particles of dust are caught in a special type of gel slung beneath the balloon. Back in the lab, the meteoroids can be analysed to reveal their precise chemical composition.

A remotely-controlled Webcam attached to the balloon recorded Saturday's ascent into the stratosphere.

Nasa issued an appeal for skywatchers to count and report back via e-mail the number shooting stars they saw during the period of the experiment.