Asteroid Imagery

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Image and caption from NASA/JPL press release photo #P40450.
Processing of this image was a joint effort between USGS at Flagstaff,AZ, Cornell University Ithaca, NY, and JPL.

Original Press Release Caption:
This picture of asteroid 951 Gaspra is a combination of the highest-resolution morphology and color information obtained by the Galileo spacecraft during its approach to the asteroid on October 29,1991. The sun is shining from the right; phase angle is 50 degrees. The base image is the best black-and-white view of Gaspra (resolution 54 meters/pixel) on which are superimposed the subtle color variations constructed from violet, green, and near-infrared (1000 nanometers) images taken in an earlier sequence at a resolution about 164 meters/pixel.

In this false-color view, the bluish areas represent regions of slightly higher albedo, which are also regions of slightly stronger spectral absorption near 1000 nanometers, probably due to the mineral olivine. These bluish areas tend to be associated with some of the crisper craters and with ridges. The slightly reddish areas, apparently concentrated in topographic lows, represent regions of somewhat lower albedo and weaker absorption near 1000 nanometers. In general, such patterns can be explained in terms of greater exposure of fresher rock in the brighter bluish areas and the accumulation of some regolith materials in the darker reddish areas.

Gaspra is an irregular body with dimensions about 19 x 12 x 11 kilometers (12 x 7.5 x 7 miles). The portion illuminated in this view is about 18 kilometers (11 miles) from lower left to upper right.

Original Press Release Caption:
This is the first full picture showing both asteroid 243 Ida and its newly discovered moon (Dactyl) 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.

*Ida's moon was named "Dactyl".