About a dozen comet particles thicker than a human hair and a least one larger than a millimeter (four hundredths of an inch) were visible to the naked eye, he said.
"We were totally overwhelmed by the ability to actually see this so quickly and so straightforwardly," he added.
The scientists estimate there may be more than a million specks of comet dust embedded in the aerogel.
Researchers will be studying the gel for years to glean clues about the origins of the solar system and the building blocks of life.
At the briefing, Brownlee unveiled the first enlarged image of a comet particle, which has already helped answer a key question about comets.
"It appears to be a transparent mineral grain, which scientifically is great, because there has been lots of discussion whether comets contain minerals, or glass, or whatever," he said.
"We've already got scientific results."
Now that Stardust's canister is safely at Johnson Space Center, mission scientists will prepare samples to send to experts around the world.
"We have something like 150 scientists worldwide poised to grab these samples in their own labs and study them," Michael Zolensky, Stardust's curator and a co-investigator, said at the briefing.
With so many qualified scientists working with the samples, results should come very quickly, he added.
Some groups will study the bulk composition of the samples, comparing them to meteorites.
Other researchers will look at the elements to learn about the history of the samples.
Additional experts will try to answer questions about whether comets delivered water and the building blocks of life to Earth.
In addition, scientists believe the spacecraft collected upwards of 200 grains of interstellar dust no larger than a micron (a millionth of a meter) in size.
The tiny grains, however, are lodged on a relatively large collector, which makes searching for them like looking for ants on a football field.
To help in this task, scientists at the University of California, Berkeley designed a computer programcalled Stardust@homethat allows individual computer-users to search through some 1.5 million images of the aerogel for the telltale tracks left by the grains.
"We already have more than 50,000 people signing up for this and we hope for many, many more [P]erhaps with this effort we'll find interstellar grains rapidly," Zolensky said.
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