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Two Very Different Asteroids
| Title |
Two Very Different Asteroids |
| Description |
The NEAR Shoemaker spacecraft has scored two important firsts in the exploration of asteroids: it's the first to orbit an asteroid, Eros, and the first to encounter a denizen of the outer reaches of the asteroid belt, the C-type asteroid Mathilde. In a scheme that reflects how they have historically been a topic for astronomy, not geology, asteroids are classified into groups based on their colors as observed through telescopes. The two major classes of asteroids are called S-types and C-types. S-types, whose colors are consistent with "stony" or rocky compositions, prevail among asteroids that orbit closer to the Sun than the mid-point of the asteroid belt. Eros and the two asteroids encountered briefly by the Galileo spacecraft on its way to Jupiter -- Gaspra and Ida -- are all S-types. C-types like Mathilde have a dark gray color consistent with a "carbonaceous" composition, rich in carbon compounds and other dark materials. They prevail in the outer part of the asteroid belt. In this montage, Mathilde (at left) and Eros (at right) are shown at the same scale, as they were imaged by NEAR Shoemaker from about 1,800 kilometers (1,116 miles) on June 27, 1997, and February 12, 2000, respectively. Mathilde is 56 kilometers (35 miles) across, and Eros is 33 kilometers (21 miles) long and 13 kilometers (8 miles) wide. However, Mathilde's brightness is greatly exaggerated for viewing purposes -- it's actually six times darker than Eros, with about the same reflectivity as soot! Built and managed by The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, NEAR was the first spacecraft launched in NASA's Discovery Program of low-cost, small-scale planetary missions. See the NEAR web page at http://near.jhuapl.edu for more details. |
| Date |
03.30.2000 |
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Eros' Bland Butterscotch Col
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PIA02475
Sol (our sun)
Multi-Spectral Imager
| Title |
Eros' Bland Butterscotch Colors |
| Original Caption Released with Image |
These color images of Eros was acquired by NEAR on February 12, 2000, at a range of 1800 kilometers (1100 miles) during the final approach imaging sequence prior to orbit insertion. A five and one-half hour long sequence of images covering visible and infrared wavelengths was taken at that time, to provide a global overview of the color and spectral properties of the asteroid. The images show approximately the color that Eros would appear to the unaided human eye. Eros' subtle butterscotch hue at visible wavelengths is nearly uniform across the surface. Two days after these images were taken, mapping by NEAR's infrared spectrometer showed that Eros exhibits a great deal more variety at longer wavelengths. These variations could be due to differences in texture or composition of the surface. Both NEAR's multispectral imager and infrared spectrometer will be used extensively during the month of March to map Eros' color and spectral properties from an altitude of 200 kilometers (120 miles). The images to be returned will show details as small as 20 meters (68 feet) across, providing a new perspective on the asteroid's many fascinating landforms discovered so far by NEAR. Built and managed by The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, NEAR was the first spacecraft launched in NASA's Discovery Program of low-cost, small-scale planetary missions. See the NEAR web page at http://near.jhuapl.edu for more details. |
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Eros in color
PIA02470
Sol (our sun)
Multi-Spectral Imager
| Title |
Eros in color |
| Original Caption Released with Image |
This color image of Eros was acquired by NEAR's multispectral imager on February 12, 2000, at a range of 1100 miles (1800 kilometers). It is part of the final approach imaging sequence prior to orbit insertion and is intended to map the color properties of Eros across all of the illuminated surface. The image shows approximately the color that Eros would appear to the unaided human eye. Its subtle butterscotch hue is typical of a wide variety of minerals thought to be the major components of asteroids like Eros. Built and managed by The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, NEAR was the first spacecraft launched in NASA's Discovery Program of low-cost, small-scale planetary missions. See the NEAR web page at http://near.jhuapl.edu for more details. |
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NEAR Road to Eros
PIA02462
Sol (our sun)
Multi-Spectral Imager
| Title |
NEAR Road to Eros |
| Original Caption Released with Image |
This montage shows a selection of images of the asteroid 433 Eros that were acquired from the NEAR spacecraft over three weeks from January 22 through February 12, 2000, as the spacecraft's distance from its target shrank from 18,000 to 1260 miles (29,000 to 2025 km). As the spacecraft closed in on its target, the resolution of the images increased from 1.7 to 0.12 miles (2.8 to 0.19 km) per pixel. At 20x8x8 miles in size (33x13x13 kilometers), Eros is the second largest near-Earth asteroid and spins on its axis once every 5 hours, 16 minutes. During the early stages of NEAR's approach, Eros appeared as a small blob only a few pixels across. The apparent size of Eros and the resolution of the pictures increased continuously, at first only slowly and later dramatically day by day until, on February 9, the level of detail visible exceeded that during NEAR's first flyby of Eros on December 23, 1998. In the last images shown here, details of Eros's surface have become visible. Heavy cratering has pockmarked the irregular asteroid's surface. One side is dominated by a scallop-rimmed gouge, and the opposite side by a conspicuous, raised-rimmed crater. Built and managed by The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, NEAR was the first spacecraft launched in NASA's Discovery Program of low-cost, small-scale planetary missions. See the NEAR web page at http://near.jhuapl.edu for more details. |
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Two Very Different Asteroids
PIA02494
Sol (our sun)
Multi-Spectral Imager
| Title |
Two Very Different Asteroids |
| Original Caption Released with Image |
The NEAR Shoemaker spacecraft has scored two important firsts in the exploration of asteroids: it's the first to orbit an asteroid, Eros, and the first to encounter a denizen of the outer reaches of the asteroid belt, the C-type asteroid Mathilde. In a scheme that reflects how they have historically been a topic for astronomy, not geology, asteroids are classified into groups based on their colors as observed through telescopes. The two major classes of asteroids are called S-types and C-types. S-types, whose colors are consistent with "stony" or rocky compositions, prevail among asteroids that orbit closer to the Sun than the mid-point of the asteroid belt. Eros and the two asteroids encountered briefly by the Galileo spacecraft on its way to Jupiter -- Gaspra and Ida -- are all S-types. C-types like Mathilde have a dark gray color consistent with a "carbonaceous" composition, rich in carbon compounds and other dark materials. They prevail in the outer part of the asteroid belt. In this montage, Mathilde (at left) and Eros (at right) are shown at the same scale, as they were imaged by NEAR Shoemaker from about 1,800 kilometers (1,116 miles) on June 27, 1997, and February 12, 2000, respectively. Mathilde is 56 kilometers (35 miles) across, and Eros is 33 kilometers (21 miles) long and 13 kilometers (8 miles) wide. However, Mathilde's brightness is greatly exaggerated for viewing purposes -- it's actually six times darker than Eros, with about the same reflectivity as soot! Built and managed by The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, NEAR was the first spacecraft launched in NASA's Discovery Program of low-cost, small-scale planetary missions. See the NEAR web page at http://near.jhuapl.edu for more details. |
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Eros Color at Higher Resolut
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PIA02492
Sol (our sun)
Multi-Spectral Imager
| Title |
Eros Color at Higher Resolution |
| Original Caption Released with Image |
As the NEAR Shoemaker spacecraft descends into lower orbits around Eros, it continually returns higher spatial resolution images of the asteroid. The true color image at left was taken February 12, 2000, from a range of 1,748 kilometers (1,083 miles), and shows details only as small as 180 meters (590 feet) across. It was taken two days before orbit insertion, as part of an image sequence designed to provide moderate-resolution color mapping of Eros at a near-constant viewing geometry. The true color image inset at right was taken February 29 from a range of 283 kilometers (175 miles) and shows much smaller details only 27 meters (89 feet) across. The higher spatial resolution (by a factor of six) brings out a whole class of surface details that were either invisible or at the margin of visibility in the earlier images. For example, the bright material on the wall of the large crater in the inset image is barely evident in the lower-resolution image at left, but by virtue of its limited spatial coverage the inset image lacks information on the crater's regional geologic setting. NEAR Shoemaker's imaging strategy makes use of both types of images, with lower-resolution images providing "context" for higher-resolution images that bring specific features into sharper focus. Built and managed by The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, NEAR was the first spacecraft launched in NASA's Discovery Program of low-cost, small-scale planetary missions. See the NEAR web page at http://near.jhuapl.edu for more details. |
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A Changing Picture of Eros
PIA03116
Sol (our sun)
Multi-Spectral Imager
| Title |
A Changing Picture of Eros |
| Original Caption Released with Image |
As NEAR Shoemaker has descended to lower orbits around Eros and returned higher spatial resolution pictures, knowledge of surface landforms has grown dramatically. The effect of changing spatial resolution can be illustrated by comparing these pictures of the large, 5.3-kilometer(3.3-mile) diameter crater taken at different distances above the surface. All of the views are shown with north to the top. The upper left picture, taken February 12, 2000, from 1,682 kilometers(1,045 miles) above the crater, shows the feature's outline with several smaller craters superimposed on its southern section. There are only hints of bright materials on the north wall of the crater. The upper right view, taken April 2 from 193 kilometers (120 miles) above the crater, provides 8.7 times higher spatial resolution. The change in appearance is dramatic, details in the craters on the south rim are clearly visible and the patterns in brightness variation on the north wall are easily discerned. However, there are only the vaguest hints of boulders on the surface. The picture at lower left was taken June 14 from 44 kilometers (27 miles)above the crater, and the picture at lower right was taken July 19 from 32 kilometers (20 miles) above the crater. These views provide 4.4 and 6times higher spatial resolution than in the view at upper right. Again, the increase in spatial resolution reveals a new level of detail. Boulders have become easily visible, as have fine, dark streaks pointed downslope within the bright material. Variations in brightness also appear at even smaller spatial scales than could be seen before. When NEAR Shoemaker flies to within 5.3 kilometers (3 miles) of Eros' surface on October 26, spatial resolution will increase by another 4 to 6times compared to the two lower views shown here. A whole new level of detail in the shapes of rocks and patterns of brightness variation will be visible - and features not yet seen at all may be revealed. Built and managed by The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, NEAR was the first spacecraft launched in NASA's Discovery Program of low-cost, small-scale planetary missions. See the NEAR web page at http://near.jhuapl.edu for more details. |
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