NASA scientists have confirmed the Stardust return capsule contains cometary samples and interstellar dust.

"The collection of cometary particles has exceeded our expectations," said Dr. Donald Brownlee, Stardust principal investigator. "We were absolutely thrilled to see thousands of impacts on the aerogel." Aerogel is a sponge-like solid made of 99 percent empty space, ideal for capturing tiny particles.

Stardust landed in Utah on Sunday after a seven-year, three-billion-mile journey in space; the samples arrived in at NASA's Johnson Space Center in Houston Tuesday.

Brownlee and other researchers will hold a press conference Thursday at 11 a.m. EST at the Johnson Space Center. Later that afternoon from 5 p.m. to 7 p.m. EST, the researchers will be available for media interviews.