Stardust used an aerogel device to capture material from the comet. The  spacecraft contained a collecting device that was over 155 square inches (1,000 square centimeters) in area that contained ninety blocks of aerogel in a metal grid. NASA scientists described it as an ice cube tray-looking contraption about the size of a tennis racket.

Its structure is made up of aerogel, a low-density solid-state material that is a very good insulator and feels like polystyrene (Styrofoam®). It is made up of a gel in which the liquid portion has been removed and replaced with gas. Some of its nicknames are frozen smoke, solid smoke, and blue smoke.

The spacecraft then flew back to Earth and, on January 15, 2006, released a sample return capsule (SRC) full of material it had captured. It was sent back into Earth’s atmosphere, where it deployed a parachute and landed in the Great Salt Lake desert near the U.S. Army Dugway Proving Grounds. The Stardust spacecraft then fired its engines and went into orbit about the Sun.

Scientists at Lawrence Livermore National Laboratory (California), along with other collaborators, are finding that its samples contain material from rocky material, which usually makes up asteroids and are normally found in the inner solar system, rather than tiny stardust material, which usually makes up comets and are normally found in the outer solar system.

Tiny grains of stardust (material formed around stars) were expected to be found on Comet Wild 2. Stardust consists of tiny grains of glass, minerals, and carbon that are less than one micrometer (one-millionth of a meter) in size. They are thought to have formed in the outer fringes of the solar system, where these interstellar particles have changed little for billions of years.

When scientists looked in the aerogel, they did find very small particles but not as many as they expected. Instead they found many relatively large particles that formed very close to the Sun when it was first forming. When the particles from Comet Wild 2 impacted the aerogel, they made deep tracks that were shaped like carrots.” Such tracks into the aerogel would have needed the strength of large particles.

They were really expecting tiny bowl-shaped tracks, much shallower than what they saw. Instead they found particles millions of times larger than the tiny interstellar stardust grains they were expecting.

The scientists also did not find particles they were expecting to find. Please read on.