"The stardust grains we discovered are typical of the kinds of dust that were available at the beginning of our solar system, these were the building blocks of the sun and planets," said Dr. Lindsay Keller, an author of the paper and a researcher in the Office of Astromaterials Research and Exploration Science at NASA's Johnson Space Center, Houston. "Comet samples are the logical place to look for preserved stardust. They formed in a region of the solar system where they escaped the extensive processing that affected other solar system materials," he said. Before the sun formed, our solar system was a swirling cloud of dust and gas, the remnants of dead stars from other parts of the galaxy. Some of this dust survived the formation of the solar system unchanged to end up in comets. These comets contain the ingredients of the early solar system, the ingredients for which came from the remnants of early stars in the universe.
"The fact that these IDPs are rich in stardust and molecular cloud material suggests that they have remained essentially unchanged from the time the solar system formed, 4.5 billion years ago," said Dr. Scott Messenger, lead author of the paper and an astrophysicist at Washington University in St. Louis.
The discovery was made possible by using a new kind of ion microprobe at Washington University, which measures isotopic ratios on scales much smaller than previously possible. This is essential for identifying stardust grains, because, "they have isotopic ratios very different from anything in the solar system," Messenger said. Most collected IDPs range in size from 5 to 50 millionths of a meter, and often contain crystalline grains clumped together in sizes of 100 to 500 billionths of a meter.