| Ultimi arrivi - Asteroids and Comets |
EROS-PIA03129.jpgEros from above (2)62 visiteNEAR Shoemaker photographed this area of Eros on December 18, 2000, from an orbital altitude of 33 Km. This part of the asteroid's surface, like many others, appears vaguely "sculptured" due to its low, elongated ridges and depressions with seemingly consistent orientations. Some of the low spots also contain accumulations of smooth, pond-like materials. Neither the surface sculpturing nor the pond-like materials are well understood, and both will be investigated in detail using even higher-resolution images from NEAR Shoemaker's low passes over Eros in early 2001. The whole scene is about 1 Km across.Ott 16, 2004
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EROS-PIA02927.jpgEros' Boulders121 visiteNEAR Shoemaker images have shown many large boulders on Eros' surface, but seldom are the boulders as big and as close as the ones in this image taken on June 20, 2000, from an altitude of 51 Km. Nestled within the 700-meter (2300-foot) diameter crater at the center of the picture are four particularly large rocks whose tops protrude out from the shadowed crater interior and into sunlight. The center boulder, the largest, is about 100 meters (330 feet) across. The whole scene is approximately 1.9 Km across.Ott 16, 2004
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EROS-PIA02905-0.jpgEros (the BIG Pseudo-Anomaly)132 visiteThis image of Eros, taken from the NEAR Shoemaker spacecraft on May 1, 2000, is among the first to be returned from "low orbit." Between May and August, the spacecraft orbited at altitudes near 50 Km or less. This will be the prime period of activity for some of the spacecraft's science instruments. The X-ray / gamma-ray spectrometer will build up maps of chemical abundances, while the laser rangefinder measures the shape of Eros to within meters (a few feet). At the same time the magnetometer will watch for indications of Eros' magnetic field and the near-infrared spectrometer will map rock types. The imager will take pictures of the entire surface of Eros that capture features as small as 4 meters (13 feet) across. This particular image, taken from an orbital altitude of 53 Km, shows a scene about 1.8 Km across. Numerous craters and boulders as small as 8 meters (26 feet) across dot the landscape. The large, rectangular boulder at the upper right is about 45 meters across.Ott 16, 2004
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EROS-PIA02492.jpgEros in true colors82 visiteAs 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 Km 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 Km and shows much smaller details only 27 meters (89 feet) across.Ott 16, 2004
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DACTYL-PIA00298.jpgAsteroid Dactyl53 visiteWithin seconds of its closest approach to the asteroid 243 Ida on August 28, 1993, the Galileo spacecraft's Solid State Imaging camera caught this glimpse of Ida's previously unknown moon orbiting the asteroid. One frame of a 15-image set designed to capture a view of Ida at the highest possible resolution landed by chance with its edge right on the little moon. The range from the spacecraft was about 2.400 Km and each picture element spans about 24 meters (80 feet) on the surface of the moon. Only a small sliver of the sunlit crescent is visible at the edge of the frame (which was shifted inward toward the center in this frame). Dactyl is approximately egg-shaped, measuring about 1.2 x 1.4 x 1.6 Km (0.75 x 0.87 x 1 mile). At the time this image was shuttered, Ida was about 90 Km (56 miles) away from the moon, outside this frame to the left and slightly below center. The smoothly curving shape of the dark edge of Ida's moon can be seen on the left. The moon's observed darkside was just barely detectable.Ott 16, 2004
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DACTYL-PIA00297.jpgAsteroid Dactyl52 visiteThis image is the most detailed picture of the recently discovered natural satellite of asteroid 243 Ida taken by the Galileo Solid-State Imaging camera during its encounter with the asteroid on August 28, 1993. Shuttered through the camera's broadband clear filter as part of a 30-frame mosaic designed to image the asteroid itself, this frame fortuitously captured the previously unknown moon at a range of about 3,900 kilometers (2,400 miles), just over 4 minutes before the spacecraft's closest approach to Ida. Each picture element spans about 39 meters (125 feet) on the surface of the moon. More than a dozen craters larger than 80 meters (250 feet) in diameter are clearly evident, indicating that the moon has suffered numerous collisions from smaller Solar System debris during its history. The larger crater on the terminator is about 300 meters (1,000 feet) across.Ott 16, 2004
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Comets-Shoemaker-Levy_9_before_collision.jpgThe Shoemaker-Levy 9 Comet just before colliding with Jupiter145 visiteCaption NASA originale:"The comet's original single nucleus was torn to pieces by Jupiter's strong gravity during a close encounter with the Solar System's largest planet in 1992. The pieces are seen in this composite of HST images to be "pearls" strung out along the comet's orbital path.
In July of 1994 these pieces collided with Jupiter in a rare and spectacular series of events". Lug 24, 2004
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