This first image of asteroid 253 Mathilde, returned by the NEAR spacecraft just before 10:00 AM EDT on June 27, 1997, was taken from a distance of 1800 kilometers (1120 miles). Sunlight is coming from the upper right. The part of the asteroid shown is about 59 kilometers (36 miles) across, and the scale is approximately 230 meters (780 feet) per pixel. The surface is heavily cratered, and the large shadowed area on the left may be a single impact gouge well over 10 kilometers (6 miles) deep. The angular form of the edge of the shadowed area suggests that large impacts may have spalled large pieces off the asteroid. This asteroid is very dark, reflecting only about 4% of the light falling on it, but was imaged easily by the sensitive NEAR multispectral camera
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.
Voir l'image PIA02476: First NEAR image of Mathilde sur le site de la NASA.
This view of 253 Mathilde, taken from a distance of about 1,200 km (748 miles), was acquired shortly after the NEAR spacecraft's closest approach to the asteroid. In this image, the asteroid has been rotated so that the illumination appears to come from the upper left. This portion of Mathilde shows numerous impact craters, ranging from over 30 km to less than 0.5 km (18.. 0.3 miles) in diameter. Raised crater rims suggest that some of the material ejected from these craters traveled only short distances before falling back to the surface; straight sections of some crater rims indicate the influence of large faults or fractures on crater formation. The number of craters as a function of size, and the number of each size within the visible area, are similar to values seen on asteroid 243 Ida, viewed by the Galileo spacecraft in 1993. A major difference between Ida and Mathilde appears to be the abundance of very large craters: Mathilde has at least 5 craters larger than 20 km in diameter on the roughly 60% of the body viewed during the encounter.
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.
Voir l'image PIA02478: Abundance of Very Large Impact Craters on Mathilde sur le site de la NASA.
Two different views of asteroid 253 Mathilde were obtained by the NEAR spacecraft on June 27, 1997. The image at left was obtained as the spacecraft approached Mathilde with its camera pointed near the direction of the Sun; only a few of the prominent ridges on Mathilde are illuminated. The visible area at left is 29 km (18 miles) high, and the phase angle (the angle from Sun-Mathilde spacecraft) is 136°. As the spacecraft receded from Mathilde, it observed the asteroid (about 60 km or 38 miles across) almost fully lit by the Sun at a phase angle of 43° (right image). Mathilde's irregular shape results from a long history of severe collisions with smaller asteroids. The largest visible crater is 30 km (19 miles) in diameter.
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.
Voir l'image PIA02479: Two Views of Mathilde sur le site de la NASA.
This image mosaic of asteroid 253 Mathilde is constructed from four images acquired by the NEAR spacecraft on June 27, 1997. This was taken from a distance of 2,400 km (1,500 miles). Sunlight is coming from the upper right. The part of the asteroid shown is about 59 by 47 km (36 by 29 miles) across. Details as small as 380 meters (1,250 feet) can be discerned. The surface exhibits many large craters, including the deeply shadowed one at the center, which is estimated to be more than 10 kilometers (6 miles) deep. The shadowed, wedge-shaped feature at the lower right is another large crater viewed obliquely. The angular shape of the upper left limb of the asteroid results from the rim of a third large crater viewed edge-on. The bright mountainous feature at the far left may be the rim of a fourth large crater emerging from the shadow. The angular shape is believed to result from a violent history of impacts.
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.
Voir l'image PIA02477: Mosaic of Mathilde sur le site de la NASA.
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.
Voir l'image PIA02494: Two Very Different Asteroids sur le site de la NASA.