NASA's Genesis spacecraft, the first mission to collect and return samples of the solar wind -- fast moving particles from the Sun -- is moving closer to launch. Scheduled for liftoff in February 2001, the mission will help scientists refine the basic definition of the Sun's characteristics, and understand how the solar nebula, a large cloud of gas and dust, gave rise to our complex solar system.
Genesis has received its final piece of science equipment: a solar wind collector made of a new formula of bulk metallic glass, composed of the same class of material as high-tech golf clubs. It and other solar wind collector tiles on the spacecraft will collect the first-ever samples of the solar wind as the spacecraft floats in the oncoming solar stream.
"Comparing differences in what the Sun and the Earth are made of yields interesting conclusions," said Dr. Don Burnett of the California Institute of Technology in Pasadena, the principal investigator for the mission and leader of the Genesis team. "What Genesis does is measure what the Sun is made of, so that many important comparisons can be made."
On its return to Earth in 2003, the sample collected by Genesis will be retrieved in midair by helicopters. Genesis will have collected elements of the solar wind such as isotopes of oxygen and nitrogen. The samples will be sent to laboratories for detailed analysis.
Bringing back samples of the solar wind will provide the next century of scientists with a databank of solar composition. Because the outer layers of the Sun are composed of almost the same material as the original solar nebula from which all our solar system came, scientists will also learn more about meteorites, comets, lunar samples, planetary atmospheres, and how these components evolved.
The mission is designed to measure the composition of isotopes in solar matter, to improve knowledge about the differing amounts of elements, and to obtain separate samples of different types of solar wind.
The body of the spacecraft contains a canister with collector plates that fold out like blades on a pocket knife to collect solar wind. The ions and particles that make up the solar wind will embed themselves and be trapped in small hexagonal plates on the circular blades.
A disk made of a mixture of metals that has properties similar to other glasses, about the size of a coffee cup lid, completes the science payload. It is a unique formulation of bulk metallic glass created especially for Genesis. The shaft on which the plates rotate is capped with the disk of new bulk metallic glass.
In an odd mix of science and sports, golfers and Genesis scientists both like bulk metallic glasses, but for different reasons. Premium golf clubs can be made with a kind of bulk metallic glass that is hard but springy. Scientists use a type that absorbs and retains helium and neon, important elements in understanding solar and planetary processes.
The new bulk metallic glass-forming alloy was designed by Dr. Charles C. Hays in the materials science laboratories of Dr. Bill Johnson of Caltech. It is a complex mixture of zirconium, niobium, copper, nickel, and aluminum. The atoms of metallic glasses solidify in a random fashion, unlike metals, which have an ordered crystalline structure. This disordered atomic state makes metallic glasses useful in a wide range of applications, from aircraft components to high-tech golf clubs. The Genesis metallic glass was prepared in a collaborative effort by Hays and George Wolter of the Howmet Corporation, Greenwich, Conn., using the same process the company uses for the high-tech Vitreloy- based golf clubs.
The surfaces of metallic glasses dissolve evenly, allowing the captured ions to be released in equal layers by sophisticated acid etching techniques developed by the University of Zurich, Switzerland. Higher-energy ions blast further into the metal's surface. When samples are back on Earth, special techniques will be used to etch the metal layer by layer, releasing the particles of gas for laboratory study.
"One exciting thing about bulk metallic glass is that it will enable us to study ions with energies higher than the solar wind. This allows Genesis to test proposals that the higher energy particles differ in composition from the solar wind," said Burnett. This will be the first time the theories about different kinds of solar wind can be tested by bringing back actual samples, he said.
To bathe in the solar wind, the spacecraft only needs to fly about 1.5 million kilometers (1 million miles) toward the Sun (about 1 percent of the Sun-Earth distance). When it is in the right position -- outside of Earth's magnetic field, between Earth and the Sun where the gravity of both bodies is balanced, called the Lagrange point -- the capsule will open its collector arrays and let ions barrage its panels.
For more information, see the Genesis home page at http://genesismission.jpl.nasa.gov/ .
Genesis is managed by JPL for NASA's Office of Space Science, in Washington, DC. It is part of NASA's Discovery Program of low-cost, highly focused science missions. JPL is a division of the California Institute of Technology.
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