This is the first full picture showing both asteroid 243 Ida and its newly
discovered moon to be transmitted to Earth from the National Aeronautics
and Space Administration's (NASA's) Galileo spacecraft--the first
conclusive evidence that natural satellites of asteroids exist. Ida, the large
object, is about 56 kilometers (35 miles) long. Ida's natural satellite is the
small object to the right. This portrait was taken by Galileo's charge-coupled
device (CCD) camera on August 28, 1993, about 14 minutes before the
Jupiter-bound spacecraft's closest approach to the asteroid, from a range of
10,870 kilometers (6,755 miles). Ida is a heavily cratered, irregularly shaped
asteroid in the main asteroid belt between Mars and Jupiter--the 243rd
asteroid to be discovered since the first was found at the beginning of the 19th
century. Ida is a member of a group of asteroids called the Koronis family.
The small satellite, which is about 1.5 kilometers (1 mile) across in this view,
has yet to be given a name by astronomers. It has been provisionally
designated '1993 (243) 1' by the International Astronomical Union. ('1993'
denotes the year the picture was taken, '243' the asteroid number and '1' the
fact that it is the first moon of Ida to be found.) Although appearing to be
'next' to Ida, the satellite is actually in the foreground, slightly closer to the
spacecraft than Ida is. Combining this image with data from Galileo's
near-infrared mapping spectrometer, the science team estimates that the
satellite is about 100 kilometers (60 miles) away from the center of Ida. This
image, which was taken through a green filter, is one of a six-frame series
using different color filters. The spatial resolution in this image is about 100
meters (330 feet) per pixel.
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