Nittler is Part of the Stardust Research Team that Discovered 7 Grains from Outside our Solar System

NASA's Stardust spacecraft, which collected comet and interstellar dust in 2004 and later delivered the tennis racket-shaped dust collectors to Earth via parachute. (Credit: NASA.)
Friday, August 15, 2014 

Where did our solar system come from? In 2006, NASA’s Stardust spacecraft returned to Earth with samples of a comet’s dust grains containing clues that could help researchers answer this question. Now, almost a decade later, scores of scientists have researched these dust particles and identified 7 grains that most likely came from outside our solar system. 

In 1999, the Stardust spacecraft launched into space aboard a Delta II rocket from Cape Canaveral Air Station, Florida. Its objective was to fly through the wake of comet Wild-2 near Jupiter and capture cometary dust in aerogel tiles and aluminum foils mounted on the front of a two-sided collector. In addition, collectors were mounted on the rear of the spacecraft to catch particles from the snowstorm of interstellar dust streaming through the galaxy. In 2006, Stardust flew by Earth and dropped by parachute the separate tennis racquet-shaped comet and interstellar dust collectors. Since then, a research team consisting of 66 scientists from 7 different countries along with 30,000 citizen scientists, self-proclaimed “Dusters” using the online Stardust@home project, have been examining millions of microscopic images of interstellar dust.

DTM Staff Scientist Larry Nittler is the 13th among the 66 authors on Stardust’s paper in the August 15th issue of Science entitled, “Evidence for interstellar origin of seven dust particles collected by the Stardust spacecraft, detailing the results from Stardust.”

Nittler used scanning electron microscope to search for the rare and tiny (smaller than one millionth of a meter) impact craters made by interstellar dust grains impacting Stardust’s dust collector trays. He also used DTM’s NanoSIMS ion microprobe to measure oxygen isotopic composition in the interstellar crater candidates. Twelve other papers about the project will appear next week in Meteoritics & Planetary Science.

"By analyzing interstellar dust, we can understand our own origins," said lead study author Andrew Westphal, a planetary scientist at the University of California at Berkeley. "Just as people go to Africa to look for fossil hominids, say, 4.5 million years old, trying to understand the origins of humanity, we want to look at stuff that helped form the solar system 4.5 billion years ago."

These interstellar dust motes Stardust returned to Earth are extremely tiny. “A trillion of them would fit onto a teaspoon,” Westphal told  "We think those are much older then the solar system, survivors of the violent process involved in converting the solar nebula into the solar system," Westphal said. "They don't fully represent what interstellar dust is like, since they had to be tough to survive, while other stuff that is more fragile did not survive well at all."

Additional tests still need to be done to confirm that these grains are indeed from outside our solar system, but Westphal and his team can comfortably say these pieces of debris are most likely from interstellar space. Until now, the origin and evolution of interstellar dust could only be observed from astronomical observations with telescopes. Today, they can be observed on the microscopic level in a laboratory or on a computer screen like Stardust@home. This is only the beginning of a very thorough look into the outer limits of our universe. 

Written by Robin A. Dienel
15 August 2014