Ida's moon: a sharper view.
Last spring, images radioed by the Galileo spacecraft from a 6-hour encounter with the asteroid 243 Ida revealed a tiny satellite orbiting this rocky body- the first moon of an asteroid ever photographed (SN: 4/2/94, p.214). NASA NASA: see National Aeronautics and Space Administration.
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Independent U.S. recently released Galileo's sharpest view of the moon, taken a year ago and radioed in June. The image of the kilometer-size, egg-shaped moon resolves features as small as 50 meters across.
The picture shows more than 12 craters that exceed 80 m in diameter, indicating that the tiny body has taken quite a battering from solar system debris. In fact, this suggests that the moon can't be more than a few hundred million years old, says Michael J.S. Belton of the Kitt Peak National Observatory Kitt Peak National Observatory, astronomical observatory located southwest of Tucson, Ariz.; it was founded in 1958 under contract with the National Science Foundation and is administered by the Association of Universities for Research in Astronomy. in Tucson. An older object this small probably wouldn't have survived the additional impacts, he adds.
Belton suggests that the direct ancestor of the moon is not the same one that fragmented to create Ida. But both the asteroid and its satellite ultimately stem from the breakup of the much larger body that formed the Koronis asteroid family he says. Infrared spectra taken by Galileo also suggest that Ida's moon isn't just a chip gouged from Ida. These data show that the surface abundance of the minerals pyroxene pyroxene (pī`rŏksēn), name given to members of a group of widely distributed rock minerals called metasilicates in which magnesium, iron, and calcium, often with aluminum, sodium, lithium, manganese, or zinc occur as X in the chemical and olivine olivine (ŏlĭv`ēn), an iron-magnesium silicate mineral, (Mg,Fe)2SiO4, crystallizing in the orthorhombic system. on the moon differs from that on Ida, says Robert W. Carlson of JPL (language) JPL - JAM Programming Language. .