The Deep Impact space probe found the first evidence that comets have ice on their dusty surfaces, raising the possibility that comets may have delivered life-giving water to a primeval Earth, NASA scientists said Thursday.

The findings were reported in an online edition of the journal Science.

The copper-tipped space probe collided with comet Tempel 1 about 83 million miles from Earth on July 4, setting off a celestial fireworks display and baring the comet's primordial interior.

Researchers analyzing data recorded by the probe's mother ship concluded that the comet has three pockets of thin ice that cover 300,000 square feet of its 45 square miles. About 6 percent of the ice is pure, while the rest is mixed with dust.

"It's like a seven-acre skating rink of snowy dirt," said Peter Schultz, a Deep Impact investigator who co-wrote the Science report.

Scientists long ago concluded that comets are frozen, dusty remnants from the formation of our solar system 4.6 billion years ago. Some have theorized that comets smashing into the early Earth delivered primitive organic compounds and water that helped give rise to life.

Scientists have identified some dust thrown off by Deep Impact's collision as being carbon-based.

Jessica Sunshine, lead author of the Science article, said in statement that understanding comets' composition can illuminate the role they played as "a possible source that delivered water to Earth."

"Add the large organic component in comets and you have two of the key ingredients for life," she said.

The Deep Impact project was managed by NASA's Jet Propulsion Laboratory in Pasadena.