NASA's Stardust Comet Probe Catches Dust from Interstellar Space

This false colour image shows a diffraction pattern from the first interstellar dust candidate Orion, collected by NASA's Stardust spacecraft in 2004. 

Credit: Zack Gainsforth

Seven tiny grains of rock captured by NASA's comet-chasing Stardust probe in 2004 may be visitors from the vast reaches of interstellar space, researchers say.

These interstellar dust motes from Stardust are fluffier and more diverse than expected, findings that could one day shed light on the origins of the solar system, scientists added.

Interstellar dust motes are bits of rock that permeate the enormous spaces between the stars.

NASA's comet-chasing Stardust probe

Supernovas and ancient stars produce interstellar dust, which contains elements such as carbon, nitrogen and oxygen that are necessary for life.

"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."



NASA launched the Stardust spacecraft in 1999 on a mission to collect dust from the wake of Comet Wild-2 (pronounced "Vilt-2").

Stardust rendezvoused with the comet in 2004 and, in 2006, returned its sample container back to Earth via parachute.

This image shows a top-down view of a dust particle impact on NASA's Stardust spacecraft Al foil collector. 

Credit: Stardust ISPE/ NRL

But while Stardust captured samples of Comet Wild-2 on one side of the craft's collector tray, the other side was pointed away from the comet to catch bits of interstellar dust in a stream emanating from about the direction of the constellation Ophiuchus.

These 12 images are a good representation of the closest images of comet Wild 2. 

The temporal sequence starts at the upper left and continues left to right on the first three rows. 

The overexposed and out-of-sequence images at the bottom are long exposures taken for autonomous tracking and yield the best jet images. 

All images were scaled to a constant image scale.

Credit: NASA Stardust

The tray was exposed to space for 195 days to capture particles in tiles of silica aerogel, a porous material resembling frozen smoke, which possesses a sponge-like structure that is 99.8 percent air.

Now, nearly a decade after Stardust's samples reached Earth, a preliminary analysis of the material suggests that seven of the dust motes the probe caught may have origins outside the solar system.

If that is confirmed, these tiny flecks of rock will represent the first specks of interstellar dust a spacecraft has ever returned to Earth.

"These are the very first contemporary samples of solid material from outside the solar system that we've identified," Westphal told reporters.

"Instead of looking at interstellar dust with telescopes, now we get to look at samples we collected from space with microscopes."

The keystoning apparatus cuts a picokeystone out of NASA's Stardust spacecraft interstellar dust collector at the Johnson Space Center in Houston. 

Credit: ESA /Rosetta /NAVCAM