Scientists have collected rare microscopic interstellar dust from Stardust, a spacecraft that's been delivering aerogel and aluminum foil dust from space to Earth.

They found seven dust motes that might came from outside the solar system, probably coming from a supernova explosion millions of years ago altered because of exposure to extreme space.

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Andrew Westphal from the University of California said that the interstellar dust are precious particles.

He said that the particles have crystalline materials like olivine, a magnesium-iron-silicate mineral, which might mean that the particles came from a disk around other stars which were modified in an interstellar medium.

The particles have a diverse chemical composition and structure, small particles are different from the big particles and may have different histories, he added.

Rhonda Shroud from the Naval Research Laboratory said that the particles collected from Stardust were a bit splattered but were very diverse.

It is sort of like a tossed salad, it was complex an agglomeration of other particles, she added.

Scientists found three particles that were a few tenths of micron across that contains sulfur compounds which might not have occurred in space.

They plan to analyze the remaining 95 percent of the foils to further understand the origins of the interstellar dust.

Aerogel-embedded particles called Orion and Hyrablook were also discovered, researchers said.

They will be subjected to further test to determine their oxygen isotope abundance, which could provide their origins.

In 1999, the Stardust spacecraft was launched to fly through the coma of comet Wild-2 and capture cometary dust using aerogel tiles and aluminum foils mounted on the front of the two-sided collector.

Its primary mission was completed on January 15, 2014, when its sample return capsule returned to Earth.