Landing data confirm Eros' primitive nature.When a spacecraft for the first time left its footprint on an asteroid this past February, it was more than an engineering feat. By landing on the city-length rock called 433 Eros (SN: 2/17/01, p. 103), the spacecraft enabled its gamma-ray spectrometer to make measurements of unprecedented accuracy. The data, collected over 7 days, support earlier evidence that this near-Earth asteroid Near-Earth asteroids (NEAs) are asteroids whose orbits are close to Earth's orbit. Some NEAs' orbits intersect Earth's so they pose a collision danger. On the other hand, NEAs are most easily accessible for spacecraft from Earth; in fact, some can be reached with much less fuel is a primitive rock, unaltered since its formation at the birth of the solar system solar system, the sun and the surrounding planets, natural satellites, dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The sun is by far the most massive part of the solar system, containing almost 99.9% of the system's total mass. , says Jacob I. Trombka of NASA's Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately 6.5 miles northeast of Washington, D.C. in Greenbelt, Md. This week, Trombka, the principal investigator Noun 1. principal investigator - the scientist in charge of an experiment or research project PI scientist - a person with advanced knowledge of one or more sciences of the gamma-ray spectrometer aboard the NEAR (Near Earth Asteroid Rendezvous) Shoemaker spacecraft, shared some of his team's findings with SCIENCE NEWS. Further details will appear in the November METEORITICS meteoritics Study of the chemistry and mineralogy of meteorite samples that have been collected on Earth and of meteors as they pass through Earth's atmosphere. These studies provide information about the age of meteorites, the conditions under which they formed, where they & PLANETARY SCIENCE planetary science or planetology, study of planets and planetary systems as a whole. Planetary science applies the theories and methods of traditional disciplines such as astronomy, geology, physics, chemistry, and mathematics to the study of . [GRAPH OMITTED] The gamma-ray spectra show that Eros has a low abundance of iron and aluminum relative to magnesium. That's the same signature found in the sun and ordinary chondrites--meteorites that rank among the oldest relics in the solar system. X-ray spectra recorded during NEAR Shoemaker's yearlong orbit of Eros had already indicated that the rock was a well-preserved chunk of the early solar system (SN: 6/10/00, p. 375), but the gamma rays Gamma rays Electromagnetic radiation emitted from excited atomic nuclei as an integral part of the process whereby the nucleus rearranges itself into a state of lower excitation (that is, energy content). reveal the elemental composition beneath the asteroid's surface--to a depth of about 10 centimeters. The gamma rays were recorded from just one spot on Eros. Other regions could have different compositions, says Trombka although that's unlikely. The X-ray spectra collected from several regions indicate that Eros has a uniform surface composition, he notes. Moreover, the craft's motion around the asteroid also reveals, that the asteroid has a uniform density. The findings suggest that Eros remains much as it was when it formed some 4.5 billion years ago. Had it undergone significant melting and cooling, for example, the asteroid's density and composition would now vary. Data from any one experiment doesn't prove that the asteroid is an unaltered relic, but the combined data make a compelling case, says Trombka. The gamma-ray data reveal, however, that Eros has less abundant sulfur than do other bodies that formed early in the solar system's life. Trombka speculates that numerous collisions with space debris could have heated the surface and caused the sulfur to evaporate. "Having a primitive body [such as Eros] come close enough to study ... brings us a little closer to understanding how our solar system formed," says Zoe M. Leinhardt of the University of Maryland University of Maryland can refer to:
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