ANSMET meteorites have had a tremendous influence on understanding of chondritic meteorites. Most ANSMET chondrites fall within previously known classes, supporting the canonical framework of nebular materials and conditions. However, some specimens fall within gaps in the existing framework. An example of this is the L/LL chondrites whose characteristics are intermediate to those of previously defined L and LL groups, suggesting a relatively smooth variation in nebular conditions and materials instead of discrete and distinct nebular zones. Other ANSMET samples have served to define previously unknown nebular materials or conditions. ANSMET meteorites help to define the distinct EH and EL chondrite groups, which represent materials that solidified under highly reducing conditions within the solar nebula. R chondrites (previously called Carlisle-Lakes-like) represent the opposite end of the spectrum, exhibiting features consistent with formation under conditions much more oxidizing than previously encountered. CR and CH chondrites are carbonaceous groups particularly rich in Fe and other nonvolatile metals, and deficient in volatile elements. These features yield important clues as to the degree of metal/silicate fractionation in the solar nebula and the mixing of materials of low- and high- temperature origin. CK chondrites are another unique group of carbonaceous chondrites partially defined by ANSMET meteorite discoveries. While most carbonaceous chondrites have experienced little thermal metamorphism, the CK chondrites exhibit equilibration temperatures as high as 850 degrees C, suggesting significant processing after incorporation into a parent body setting. An unusual degree of thermal processing of ordinary chondrites is also suggested by several ANSMET specimens exhibiting features consistent with melting.

The geology of the asteroids
Meteorites are fragments of debris produced during energetic collisions between parental bodies in the asteroid belt. Thus meteorites represent not only samples of the surfaces of individual asteroids but their interiors as well. The stochastic nature of this process means that the full range of asteroidal materials is not represented by what falls to Earth over a short period of time. The recovery of large numbers of Antarctic meteorites, which represent an unbiased, long term collection, has provided tremendous advances in our understanding of the asteroids. ANSMET meteorites have shown that the asteroids are not simply a collection of a few dozen "primitive" bodies, with a few more complex bodies thrown in; instead we see a set of complex, miniature planets, exhibiting features consistent with gradational levels of planetary processing, involving both traditional and decidedly exotic geological activity. As noted earlier, ANSMET meteorite finds have extended the known boundaries of parent body metamorphism and shown that impact processing has had an extensive influence on the evolution of asteroids. ANSMET recoveries have vastly improved our understanding of previously known igneous meteorites by extending the range of materials known to exist on these parent bodies. Antarctic meteorites from the Howardite-Eucrite-Diogenite clan, thought to be samples from the surface of the asteroid 4 Vesta, portray a parent planet with a rich history of differentiation, partial melting, fractional crystallization and crystal settling. At the same time, new aubrite specimens have strengthened the case for their origin as products of partial melting of an E chondrite parent. ANSMET meteorites have revealed the presence of many more disrupted parent bodies than previously thought, through the presence of iron meteorites with unique compositions. ANSMET meteorites have provided many new samples of previously unique igneous lithologies, revealing them to be samples of geologically active parent bodies rather than oddballs or curiosities. These include the angrites and brachinites, distinct olivine- and feldspar- rich igneous rocks suggesting various degrees of partial melting on primitive, chondritic parent bodies. They also include much more complex scenarios of partial melting and mixing of partially differentiated protoplanets, as evidenced by the acapulcoites, lodranites and ureilites. Finally, it should be noted that there are still some achondrites of "unknown" affinity within the ANSMET collection, and only further recoveries can establish their place in the history of the solar system. ANSMET meteorites continue to reveal a new level of complexity among the asteroids, and serve as important analogs now that direct study of asteroids by spacecraft has begun.

Mass transfer between the planets, and the geology of the moon and Mars
One of the most important discoveries based on ANSMET meteorites was that some samples were actually derived not from the asteroids but from the moon and Mars. The conventional wisdom 20 years ago was that any specimens knocked off a planet- sized body by an impact would be altered beyond recognition if not completely vaporized. This paradigm was completely overturned by the discovery of ANSMET meteorite ALH81005, an anorthositic breccia so similar to Apollo lunar highlands samples that all investigators agreed it had to have come from the Earth's Moon. Since that time ANSMET has recovered many more lunar specimens, providing a random, global sample of the lunar surface, illustrating the global distribution of basaltic and anorthositic lithologies, and confirming bulk lunar characteristics. Since that time, several researchers have created models examining the pathways and predicting the number of meteorites that may be reaching our planet from various sources. Equally important was the discovery of new members of the SNC group of igneous meteorites, whose young crystallization age distinguished them from "normal" achondrites. Speculation as to the parent planet of the SNC meteorites effectively ended when it was found that shock-produced glass in the ANSMET meteorite EETA 79001 contained a suite of trapped noble gases identical to the current atmosphere of Mars, as measured by the Viking landers. These specimens have become windows into the geology of Mars, as the only available samples from that planet. In general terms, their study has provided an absolute chronology for igneous events on Mars; allowed direct study of the composition and properties of the Martian crust, core and bulk planet; provided information on the size and behavior of the volatile inventory of the planet; and opened doorways to exploration of the possible support of life on Mars sometime in the distant past; and showed the presence of organic compounds. In addition, the martian meteorites provide the best possible "analog" for upcoming robotic and sample return missions to Mars.

Stardust
One of the most exciting revolutions in meteorite studies is taking place today, and ANSMET meteorites play a subtle but important role. As already noted, chondritic meteorites are thought to represent samples of the solar nebula, and are carefully studied to help understand the kinds of materials and conditions that were present at the beginning. But some chondrites exhibit puzzling isotopic signatures, particularly among the noble gases, that do not make sense in terms of the bulk qualities of the solar nebula. Researchers expended great effort to find the carriers of these strange isotopic signatures, in the hopes that a more concentrated sample would yield clues as to their origin. This research required breaking down valuable samples into their most stable, inert components through extremely destructive mechanical and chemical extractions. Such destructive techniques are hard to justify when samples are rare, and hard to replace- but the abundant chondritic material represented by Antarctic meteorites help make this work plausible. Eventually, carrier phases of these strange isotopic signatures were isolated as dispersed, very rare components of chondritic meteorites. These phases include diamond, silicon carbide, aluminum oxide, graphite, and other refractory minerals, each with a distinct isotopic signature that could not have been produced by known solar-system processes. Different stellar environments provide the only plausible source for these grains. Many distinct environments have been isolated so far, including the extended envelope of red giant stars, the explosive shell of recent supernovae, and active Wolf-Rayet stars). In essence, these grains derived from meteorites provide us with samples of different stars, and allow researchers to perform astrophysical studies based on samples rather than observation or theory. Although this field is literally only a few years old, it is already revolutionizing our understanding of stars and the interstellar medium. Without the large numbers of readily available samples provided by ANSMET and other Antarctic meteorite sources, this kind of research could not have progressed so rapidly.