Comet, Wild

Although information on the chemical composition and reactivity of interstellar ices can be obtained only from remote observations and laboratory simulations, cometary ices and dusts are subject to direct studies, eg within Vega and Giotto (comet Halley), Stardust (comet Wild 2) and Rosetta (comet Churyumov-Gerasimenko) missions (Figure 8.12). 

Presolar grains are found in small quantities (with concentrations of ppb to several 100 ppm, see Table 2.1) in all types of primitive Solar System materials (Lodders Amari 2005 Zinner 2007). This includes primitive meteorites (the chondrites), IDPs, some of which might originate from comets, Antarctic micrometeorites (AMMs), and samples from comet Wild 2 collected by NASA s Stardust mission. Presolar grains are nanometer to micrometer in size. The isotopic compositions, chemistry, and mineralogy of individual grains with sizes >100 nm can be studied in the laboratory. Important analysis techniques are secondary ion mass spectrometry (SIMS) and resonance ionization mass spectrometry (RIMS)... 

With the success of the Stardust mission, tests of our models for solar nebula, and thus protoplanetary disk evolution, are no longer limited to asteroidal bodies (meteorites), but now can be applied to cometary bodies as well. Stardust returned dust grains that were ejected from the surface of comet Wild 2, a Jupiter-family cometthatis thought to have formed at distances of >20 AU from the Sun (Brownlee et al. 2006). Thus, we now have samples of materials from the outer solar nebula that can be studied in detail. 

In order to consider the processes of dust coagulation in the early Solar System, we first review the characteristics of this material. Of considerable importance is the fact that these samples - represented principally by chondritic meteorites, but also by IDPs and by samples from Comet Wild 2 collected by the Stardust mission - all come from parent bodies of different kinds. As a result, even the most primitive of these materials has been processed, both physically and chemically, to different degrees. The processes that affected Solar System dust may have occurred in different environments such as the solar nebula (e.g. evaporation/condensation, annealing) and asteroidal parent bodies (aqueous alteration and/or thermal processing, mild compaction to extensive lithihcation). A major challenge is to understand the effects of this secondary processing. 

Both the analysis of Comet Wild 2 dust particles (Brownlee et al. 2006) and infrared spectroscopy of dust particles from comets Halley, Hale-Bopp, and Tempel 1 (Lisse et al. 2006) have shown that crystalline silicates are common constituents of comets. The presence of crystalline silicates in comets indicates that the crystallization of amorphous interstellar silicates occurred in the comet-forming region... 

Fortunately, and perhaps surprisingly, the Universe provides a means to address these important questions. Today we are witnessing as the answers emerge to these age-old questions. We now know that asteroids and comets of the Solar System have preserved a detailed record of the dramatic events that four billion years ago gave birth to our planetary system in only a few million years. Gravity and radiation pressure conspire to deliver almost pristine samples of the early Solar System to Earth in the form of meteorites and interplanetary dust particles. We have also taken this process one step further with the successful return of particles from the coma of comet Wild 2 by NASA s Stardust mission. Detailed chemical and mineralogical analyses of these materials allow for the reconstruction of the history of our planetary system. 

The obvious source of comet samples is by direct collection at a comet with Earth return. Stardust, the first comet sample mission (Brownlee et al., 2000), will collect the positively identified particulate samples from a comet and return them to Earth. Stardust, a NASA Discovery mission, will collect thousands of particles from the coma of SP comet Wild 2 and return them in 2006. Hopefully future sample return missions will, in addition, recover subsurface samples of ice and dust and return them to Earth with cryogenic preservation. 

Comet, wild water Fanlaslik spray Formula 409 Mr. Clean Murphy Pinesol... 

This photograph of Comet Wild-2 was taken by the Stardust spacecraft s navigation camera on January 2, 2004, at a distance of about 300 miles (500 km) from the comet. (NASA/Photo Researchers, Inc.)... 

Comet and Interstellar Dust Analyser (CIDA) is a time-of-flight mass spectrometer aboard NASA s Stardust spacecraft launched in February 1999 to explore comet Wild 2 (mission 1999-2006). CIDA has been fabricated by Hoerner Sulger, under contract by the German Space Agency. 

Stardust, a U.S. National Aeronautics and Space Administration (NASA) spacecraft, used silica gel to collect particles of debris from the tail of comet Wild-2. 

The mission for this spacecraft was to collect dust and carbon-based samples from the comet Wild 2. 

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