The Stardust Mission
Kye Ewing - February 1, 2000
We earthlings are used to being able to use our senses to learn about the nature and composition of things. It would be difficult to tell the difference between a porcupine's quills and a flower with soft, fluffy spikes without the sense of touch! This however is exactly what theorists have been limited to when trying to make conclusions about the Universe outside our neighborhood of the solar system. Our sense of touch has so far only reached past Earth with missions to the Moon and nearby planets. However, a giant leap forward in our knowledge about what the Universe is made of is about to occur. The StarDust spacecraft will collect samples of the basic building blocks of our solar system and samples of matter that formed outside the solar system, neither of which have ever been sensed directly.
On February 9, 1999, the StarDust spacecraft was launched on a seven year journey to pass very close to Comet Wild2. The craft will sweep past the comet at 136,000 MPH (twenty times the speed of a bullet) and then return to earth with the first samples ever recovered from such a distant object. Scientists are anxious to get a look at the returned material, since the comet originated in the Oort Cloud of our solar system. The primitive particles being collected could reveal secrets to the formation of our solar system and could lead to more accurate theories of stellar evolution.
Acting like a catcher's mitt, a substance called "aerogel" will intercept delicate comet particles from Wild2's gaseous corona. The trick will be to capture these tiny particles without damaging or changing them. Developed in the 1930's, aerogel was largely ignored until its potential began to be realized in the late 1970's when the aerospace industry went looking for a substance that was extremely light weight and highly heat resistant. This strange form of silicone, 1000 times less dense than the silicone glass we are used to, was most recently used on the Sojourner Mars Rover in 1997. As night fell on Mars, the temperature dropped to around -88ºF. The sensitive instruments inside the rover remained at a comfortable 70ºF, preventing damage from extreme temperature changes and conserving fuel which would otherwise be needed to keep things from freezing.
The primary goal of the StarDust mission is to capture both comet samples and interstellar dust and return them to earth. Aerogel fit the bill, with very high damping properties for all types of energy transfers. This is a critical feature, since the particles will disburse a lot of energy when they are caught by the aerogel and that usually involves the creation of a LOT of heat! The impact will be so powerful that with any other known substance the particles would either be vaporized or become too distorted to be useful for study. When the dust particles hit the aerogel they will drill through the material, gradually slowing down, creating furrows that scientists can use to track the paths of the tiny stardust particles. Like an airplane landing on a runway, they will be easily found at the ends of the furrows. The same aerogel mitt will be used during the journey to collect interstellar dust particles. This dust is part of a newly discovered beam of particles streaming into our solar system from other stars. The direction of the furrows produced will tell researchers whether they are looking at comet dust or interstellar dust, since the mitt is two-sided and one side will face the comet while the other side will face the interstellar dust stream.
After the encounter with Wild2, the aerogel collector will be retracted into a return capsule for the trip to Earth. Two years later the journey will end when the craft lands (?) on the desert of Utah. Scientists expect to capture about 1,000 particles large enough for individual study, and millions more smaller samples which can be studied in groups. The craft will also take the most detailed photographs ever made of a comet's surface features. It is hoped that the detailed study of these particles may even reveal information about the origins of life on earth. This mission could provide ground truth information on interstellar models and possibly reveal processes that were previously unforeseen.
* 5/99 "Aerospace America" magazine by AIAA
* NASA JPL's Stardust homepage
* NASA's Liftoff Academy