Those that closely follow space-related news will no doubt have already heard of Stardust@Home, but I decided I would wait until the Stardust probe made it safely back to Earth before I wrote about it. Well, that has happened, NASA’s Stardust probe has returned safely (an infrared image of a helicopter landed at the touchdown site is shown at the right), hopefully bearing millions of particles shed by Comet Wild 2 (pronounced “Vilt 2″ and shown in a composite image below) and as many as 100 particles from the Interstellar Medium outside the solar system itself. The mission is something of a milestone, as it represents only the second time that particles have been successfully returned from beyond our Moon (Genesis was the first), and it may give us our first opportunity ever to see particles from a comet and from the Interstellar Medium.
Stardust flew past comet Wild 2 on January 2nd, 2004 collecting dust particles as it flew through the comet’s coma. These dust particles embedded themselves in Stardust’s remarkable aerogel collectors, dissipating their fantastic energies without destroying themselves in that amazing material. Mission scientists expect that millions of tiny particles were collected in the cometary flyby, among which perhaps as many as 1,000 will be large enough for a detailed compositional analysis. As a bonus, Stardust flew through a newly-discovered track of interstellar particles coming from the direction of the constellation Sagittarius (sounds like the plot from Contact). Perhaps as many as 100 particles were collected in that encounter, and particles are expected to be very very small.
The job of detecting and isolating fewer than 100 interstellar needles in a very expensive haystack falls at the feet of Dr. Andrew Westphal of UC Berkeley and the Planetary Society. Scientists working for Westphal will process the aerogel samples by sending them into a special robotic microscope that detects and images particle tracks in the aerogel (see the image to the right). This robotic microscope (pictured below, left) will be used to detect the millions of particles from Wild 2’s coma, flagging the deepest tracks for direct analysis and sample extraction. However, the smaller particles that are too small to be analyzed by other instruments will not penetrate as deeply, and at those shallow depths there are hundreds of tiny fractures and imperfections in the aerogel material.
This is not a problem for the coma fragments because 1 million/1 thousand is still pretty good signal/noise ratio, but if 100 particle tracks from the interstellar medium are buried in perhaps thousands of aerogel imperfections, the robotic detection system will not provide accurate results. Thus, all of the images from the segments of the aerogel exposed to the interstellar particles will be pooled and sent out to thousands of volunteer image analysts. The Stardust@Home website (linked above) provides details on how to volunteer. Prospective volunteers must first go through a short training exercise online and pass a quiz before they are deemed qualified to tell genuine particle tracks from mere cracks.
The robotic microscope takes a series of images focused on a range of depths at each location on the collector surface. Unlike the image above, the tracks will appear as small circles when viewed from above. Every image in which particle tracks are detected are then sent to a large number of other volunteers (approximately 100), and high-scoring detections in which a significant number of volunteers find that same track are then sent to scientists in Westphal’s lab for expert analysis.
Amateur astronomy is one of the few areas of science in which non-scientist amateurs can productively participate. Among other legitimate scientific activities, amateur astronomers monitor supernovae and variable star brightnesses, and search for comets and asteroids. Stardust@Home represents a new field of amateur scientific contribution: astrogeochemistry. This may be a one-of-a-kind chance to spend a few hours advancing science, so don’t miss out! Each interstellar grain of material detected will be one more than all of humanity has ever before seen.
