On January 15, NASA's Stardust mission will blaze through Earth's atmosphere, returning a precious cargo of comet and interstellar dust. Those of you lucky enough to live in Northern California or Nevada should be able to see the "shooting star" of this re-entry around 1:15am Pacific Time on the morning of the 15th.
The Stardust mission was built to collect two samples of dust. One sample comes from the comet Wild 2 (pronounced like "Vilt") and was collected in January 2004, and about 1000 dust grains, or about 1/1000 of an ounce of comet material, will be returned to Earth and analyzed by scientists. The other dust sample is about 100 particles of interstellar dust, or dust from outside our own Solar System. This dust was created by other stars, and very little of it has ever been found or studied.
To collect dust without destroying it is hard, because the spacecraft was moving at 13,000 miles per hour relative to the comet dust. The spacecraft used something like a giant tennis racket filled with aerogel, or a foamy glass. I once visited the primary scientist in charge of the mission, Dr. Donald Brownlee, and he let me hold a chunk of aerogel. It is so light, you can barely feel it in your hand.
So, after almost seven years in space and three billion miles of travel, Stardust is almost home. Here's to a safe return!