March 1, 2006
Last month a flying saucer hurtled through the Earth’s atmosphere at record-breaking speeds, creating a spectacular fireball in the sky for early-rising sky-watchers before deploying a parachute and floating to a gentle rest on the floor of the Utah salt flats. Although the saucer didn’t contain any little green men, it carried something just as exciting to the team of scientists that anxiously awaited its return: dust.
Seven years ago, the National Aeronautics and Space Administration, better known as NASA, launched the Stardust mission with the aim of collecting and returning the first-ever comet samples to Earth. This was the first sample return mission from a solid solar system body since the Apollo missions to the moon.
Two years ago, after traveling more than 3 billion kilometres at an average speed of 78,000 km/h, the Stardust probe rendezvoused with comet Wild 2 (pronounced Vilt 2) and captured dust samples from the comet’s tail using a tennis racket-sized collector. This collector was made from a revolutionary material called aerogel, a rigid silica-based sponge that holds the record as the lowest-density solid ever created.
Then on January 15th of this year, after an additional one-and-a-half billion kilometre journey home, the capsule containing the precious cargo successfully returned to Earth. After examining the capsule at the Johnson Space Center in Houston, TX, NASA scientists believe they've captured thousands of comet particles in the areogel collector, most of them smaller than the diameter of a human hair!
By building a collector out of variable density aerogel, NASA scientists were able to prevent the comet particles from simply smashing into the speeding spacecraft’s collector; instead, the particles gently slowed down as they embedded themselves within the material and in doing so, remained intact. Aerogel was also chosen for its transparency, which makes finding the embedded particles much easier than if an opaque material had been used.
So, why are scientists so excited at the chance to get up close and personal with some bits of dust?
Comets are like ancient time capsules of the solar system; they are made up of left-over solar system debris, after its formation 4.6 billion years ago. Many comets – such as comet Wild 2 – have remained largely unchanged throughout this time, and could help scientists to better understand the formation and evolution of the solar system, by providing a “snapshot” of its early conditions.
The Stardust mission, however, captured more than just comet dust. On its way to comet Wild 2, the spacecraft was instructed to periodically expose the reverse side of its collector to space. This side of the collector, scientists hope, has successfully captured dust particles spewed into the galaxy by dying stars - particles that NASA scientists are hoping could reveal clues about the inner workings of stars and the composition of interstellar space. Hence the name: Stardust.
Based on previous measurements of the density of interstellar space, scientists estimate that the collector managed to capture a mere 45 grains of star dust. NASA now faces the huge task of examining 1.6 million images of the aerogel collector in search of a scant, few dozen particles - a task they liken to finding 45 ants on a football field.
So, here’s where YOU are needed! To speed things up, NASA is enlisting the public's help to sort through the images and to identify the interstellar particles embedded in the collector by searching for carrot-shaped tracks formed by the particles as they tore through the aerogel before finally coming to a stop (see picture).
Although you’d be working for NASA, the whole process isn’t as complicated as you might think. The interactive, Internet-based search, called Stardust@home, asks interested volunteers to complete a web-based training session followed by a test that must be passed in order to participate in the project…I know what you’re thinking: do I really want to volunteer to take a test? But come on, there’s no grades involved; and besides, how often do you get the chance to work for NASA, for goodness’ sake?
After passing the test you’ll be able to download images from the collector along with a virtual microscope that will work on your own computer. There’s no minimum amount of work involved, so you can scan as many or as few of the images as you want.
Any particles that are found and confirmed will be removed for study and the original discoverers will be given the honour of naming it, as well as appearing as a co-author on any scientific paper announcing the particle’s discovery. The search is scheduled to begin in March and is expected to be completed by October of this year.
So, are you excited at the prospect of finding that first track? Then log on to the Stardust@home website to pre-register and get ready to make history.
For more information about the mission check out:
For more information about the Stardust@home project and how you can participate, check out:
For more current science online check out the Ontario Science Centre’s website:
Suzanne Taylor holds an honours bachelor's degree in astrophysics from the University of Toronto and spent four years developing public programs and exhibits at the Ontario Science Centre before making the switch to journalism. She is currently enrolled in the Masters program in journalism at the University of Western Ontario and hopes to write about science and society after graduating this spring.