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Space Topics: Stardust

Mission Objectives

Wild 2
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A view of both the 4-kilometer (2.5-mile) nucleus and the jets of comet Wild 2 is made possible by the superimposition of a long- and a short-exposure image. Credit: NASA / JPL

Stardust’s principal goal was to collect dust from comet Wild 2 and return it to Earth for scientific investigation. If successful, it will be the first mission to return samples from beyond the Moon.  It will be considered a success if its sample return capsule lands safely on Earth with more than one thousand particles of cometary dust larger than 15 microns in diameter.  Secondary goals included the collection and return of interstellar dust particles and the acquisition of images and data of the comet nucleus during the flyby.

Scientists hope to learn a great deal from the samples, not only about the nature and composition of comets, but also about the history of the solar system. This is because comets have remained almost unchanged since the formation of the solar system 4.5 billion years ago. At that time, the protoplanetary disc of gas and dust surrounding the Sun congealed into the separate planets we know today. In the far reaches of the solar system, however, the particle cloud was not dense enough for the accretion process that produced the planets to take place. As a result, the region known to us as the Kuiper belt remains populated by large and small iceballs. Far as they are from the Sun, they have not been modified by the effects of solar heat and radiation and have remained much as they were billions of years ago.

When these iceballs are deflected from their ancient orbits and stray into the inner solar system, they appear to us as comets -- ancient fossils of the primordial solar system. By comparing them to the highly processed and differentiated world we see around us, scientists hope to be able to draw conclusions about the history and development of the planets.

Furthermore, many scientists believe that comets supplied Earth with water and organic compounds, during an intense cometary bombardment of the young planet that ended 3.9 billion years ago. Studying actual cometary samples will help scientists substantiate the theory, refute it, or -- most likely -- revise and enlarge their knowledge of the origins of life on Earth.

Stardust's samples will be brought back to laboratories to be analyzed for its physical properties, including:

  • elemental makeup;
  • the proportions of isotopes of different elements;
  • mineralogical and chemical properties;
  • and possible biogenic properties.

The samples of comet dust will help scientists understand the processes and conditions that prevailed when the Sun and the solar system were forming.  Specific questions that the Stardust team will be addressing include:

  • How do the particles compare to other primitive materials, such as meteorites?  Can their differences illuminate the different conditions that existed from place to place within the ancient solar nebula?
  • How were these materials transformed within the solar system by forces such as heating and exposure to ultraviolet light?
  • How were they distributed among planetary bodies, and in what molecular and mineral forms?
  • For the interstellar grains, what can they tell us about the compositions and life cycles of nearby stars?

Answering these questions will help researchers find similar conditions in other parts of the universe -- and maybe even find life there, too.