Astronomy - February 2014

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Some particles even preserve remnants

of presolar silicate and organic grains, from

which scientists can learn about processes

occurring in other stars and in the inter-

stellar medium (the space between stars).

Researchers find the organics in cosmic

dust particularly intriguing because these

grains could have seeded the early Earth

with the raw materials necessary for life.

The Stardust mission

Rather than waiting for cometary and

asteroidal dust to fall on us, two spacecraft

missions have returned dust particles from

WHAT IS AEROGEL?

COSMIC DUST?

PARTICLES FROM THE STARDUST MISSION

Meenakshi Wadhwa is director of the Center

for Meteorite Studies and a professor in the

School of Earth and Space Exploration at

Arizona State University. She wrote this article

while appointed as visiting scientist at the Lunar

and Planetary Institute in Houston.

NASA’s ER-2 high-altitude aircraft carries a Large Area Collector cosmic dust sensor under its wing. When the aircraft reaches 65,000 feet (19,800 meters), the

clamshell-like doors (inset) open to reveal plates coated in silicone oil that trap dust particles.

Aerogel is a silicon-based solid with a

density about 1,000 times less than typ-

ical glass and a sponge-like structure

that is 99.8 percent air. It was devel-

oped by American scientist Samuel Ste-

phens Kistler in 1931. The block of

aerogel above is similar to those used in

the Stardust collector tray.

The main image shows two

comet particle tracks in Stardust

aerogel. The longer one stretches

0.43 inch (1.1 centimeters) while the shorter measures 0.33 inch (0.85cm). The five other

images are comet particles found toward the end of the two tracks.