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| Ultimi arrivi - 433-Eros: Pictures, Facts and Legends |
M0132558188F4-pseudoparabola.pngThe "Pseudo-Dish" is gone...103 visiteUn nuovo "tassello", nella Saga delle Leggende di 433-Eros: la "Parabola".
In questo frame, che riprende il nostro "oggetto misterioso" da un angolo visuale opposto rispetto a quello solito (e cioè l'angolo visto e stravisto nelle immagini che popolano Internet), anche l'Osservatore più sbadato potrà vedere e verificare che il rilievo che, per alcuni Appassionati di Anomaly Hunting, sembrava e/o assomigliava e/o era un oggetto discoidale (una sorta di "Parabola per la Trasmissione e/o la Ricezione di Segnali", si è detto e scritto), è in realtà un boulder vagamente rettangolare, che accede ad un outcrop di modeste dimensioni.
Maggiori dettagli ed informazioni al riguardo seguiranno nell'articolo che chiuderà la "Trilogia di 433-Eros", di prossima pubblicazione su TruePlanets.
Per Vostra opportuna informazione, il "Rilievo Controverso" (chiamiamolo in questo modo "neutro", così non facciamo torto a nessuno) si trova alle seguenti coordinate: 14,46° Latitudine Nord e 256,77° Longitudine Est). MareKromiumAgo 22, 2008
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20000410.jpgDifferent Lights, Different Visions59 visiteDuring the 28 days the NEAR Shoemaker Spacecraft circled Eros in a 200-Km (such as approx. 124-mile) altitude orbit, it imaged parts of the surface under a variety of lighting and viewing conditions.
The different views of the surface allow study of small-scale morphology, analysis of albedo and color variations, and construction of topographic models from stereo images.
This image, taken April 2, 2000, from a range of 199 Km (about 123 miles), shows the effects of lighting changes. At the bottom of the frame, sunlight illuminates the surface at a grazing angle. The strong shadows bring out subtle landforms like the gentle undulations in the surface, visible at the lower center.
At the top of the frame, sunlight strikes the surface at a high angle and shadows become subdued, bringing out brightness variations like those on the wall of the large, 5,5-Km (3,4-mile) diameter crater at left.
(Image 0130112939)MareKromiumAgo 11, 2008
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20000411.jpgEros' North Polar Region (natural colors; credits: Lunexit)56 visiteFor much of the past five weeks, imaging activities on the NEAR Shoemaker Spacecraft have focused on the high Northern Latitudes of Eros.
The point at which the Sun is directly overhead - known as the "subsolar point" - has been steadily moving from Eros' Northern Regions toward the Equator as the Asteroid's seasons progress.
As this happens, the Northern Hemisphere is illuminated less and less, and previously dark Southern Latitudes progressively come into view.
In this image, taken March 19, 2000, from a range of 205 Km (approx. 127 miles), the asteroid's North Pole is in the upper right of the frame. The whole scene is 7,4 Km (4,6 miles) across.
(Image 0128883708)MareKromiumAgo 11, 2008
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20000418.jpgUp-close and personal (natural colors; credits: Lunexit)54 visiteSince April 11, 2000, the NEAR Shoemaker Spacecraft has orbited Eros at an altitude of about 100 Km (approx. 62 miles) from the Asteroid's Center. Images acquired from this orbit will be used to make a HR map of the illuminated portion of the Asteroid. Each spot on the surface will be imaged under a variety of lighting and viewing conditions to bring out different features.
In this image, taken April 17, 2000, from a height of 101 Km (approx. 63 miles), the shadows highlight small-scale surface features. The surface is pockmarked with craters ranging in size up to the 2,8-Km (1,74-mile) diameter crater in the center of the image. The smallest craters which can be resolved are about 20 meters (65 feet) across.
In lower right corner of the image, 20-meter boulders can be seen that were not evident in images from higher altitudes.
(Image 0131288775)MareKromiumAgo 11, 2008
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20000428.jpgGroovy!... (natural colors; credits: Lunexit)57 visiteNEAR Shoemaker returns images that reveal not only what makes Eros distinctive, but also what it shares with other asteroids. This image, taken April 8, 2000, from an orbital height of 210 Km (about 131 miles), shows several of the linear troughs or "grooves" that mark the Asteroid's surface.
The largest one in this image, just to the right of the shadowed crater in the lower central part of the frame, is nearly 200 meters (656 feet) across. Grooves are also found on other asteroids and small asteroid-like moons, especially the Martian moon Phobos. They are thought to form when regolith - the loose surface material thrown out of impact craters - drains into subsurface cracks.
(Image 0130614349)MareKromiumAgo 10, 2008
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20000309.jpgOblique view of the "Large Crater" (natural colors; credits: Lunexit)54 visiteThis image, showing an oblique view of Eros' "Large (central) Crater", was taken at a resolution of about 20 meters (65 feet) per pixel. The brightness or albedo patterns on the walls of this crater are clearly visible, with the brighter materials near the tops of the walls and darker materials on the lower walls. Boulders are seen inside this crater and the smaller nearby craters. The higher density of craters to the left of the large crater implies that this region is older than the smoother area seen associated with the Saddle Region on the opposite side of the asteroid.
(Image 0127591846)MareKromiumAgo 08, 2008
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20000320.jpgThe North Polar Region of 433-Eros (natural colors; credits: Lunexit)56 visiteOn March 11, 2000, this image of Eros' North Polar Region was acquired by the imager on the NEAR Shoemaker Spacecraft, from a range of 206 Km (127 miles).
The area shown in the image is 10 Km (6,2 miles) across. Most of the North Polar Region is heavily cratered but the region to the left (part of the "Saddle") has a lower crater density, indicating that the surface has been modified since it first formed.
Eros' rotational axis lies nearly parallel to its orbital plane, much as with the planet Uranus, giving the asteroid exaggerated "seasons".
Now, it is Northern Summer and the North Pole is in continuous sunlight. The Sun will set there this June, at Eros' equivalent of Earth's Autumnal Equinox. At that time, Eros' South Pole will begin 12 months of continuous illumination while the North Pole shall remain in darkness.
(Image 0128166012)MareKromiumAgo 08, 2008
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20000322.jpg433-Eros in HR (True Colors; credits: NASA)62 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 1748 Km (about 1083 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 Km (about 175 miles) and shows much smaller details only 27 meters (89 feet) across.
The higher spatial resolution (by a factor of 6) 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.
(Product of images 0125748893, 0125748895, 0125748897, 0127229466, 0127229468, 0127229470)
MareKromiumAgo 08, 2008
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20000405.jpgOld Craters (natural colors; credits: Lunexit)59 visiteEros' many craters have a range of ages dating back to the last time the asteroid's surface was "wiped clean" by geologic processes. This NEAR Shoemaker image of the tip of the asteroid, taken March 6, 2000, from a range of 201 Km (about 125 miles), shows craters with a variety of shapes and sizes.
When small craters first form, they typically have sharp rims and round floors. As they age, progressively smaller craters are superimposed, rounding the rims and pitting the walls and floors until the original underlying crater becomes almost unrecognizable.
(Image 0127738155)MareKromiumAgo 08, 2008
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20000222.jpg54 visiteThis image mosaic of Eros was taken by the NEAR Spacecraft on Feb. 18, 2000 from a range of 224 miles (about 361 Km). The smallest detail visible on the surface is about 115 feet (35 meters) across.
At the time the Spacecraft was over the shadowed Southern Hemisphere, looking North at a crescent Eros.
Although this view of Eros is similar to others that have been returned, the coverage at different illumination and viewing geometries provides important information on the shapes of landforms.
(Mosaic of images 0126286145, 0126286419, 0126286483)MareKromiumAgo 08, 2008
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20000225.jpgThe "Two Faces" of Eros... (natural colors; credits: Lunexit)55 visiteOn February 23, 2000, the NEAR spacecraft obtained a sequence of image mosaics showing Eros' surface as the asteroid rotated under the Spacecraft. At that time the range to the surface was approx. 355 Km (about 220 miles). These two mosaics, part of that sequence, show the stark beauty of the two opposite hemispheres.
The smallest detail visible is 35 meters (120 feet) across. The top mosaic shows wavy brightness banding exposed in the interior walls of the Saddle. In the bottom mosaic, similar banding is visible in one of the craters near the limb at left. To the right, the angle of the illumination accentuates the quasi-linear troughs near the Terminator.
Successful firing of NEAR's thrusters yesterday, February 24, placed the Spacecraft on course for insertion into the next lower orbit, at a 200 Km (about 120 miles) altitude. Images from that orbit, commencing in early March, will have nearly twice the spatial resolution of data returned so far.
(Product compiled from images 0126712790, 0126713054, 0126713230, 0126723526, 0126723790, 0126723878)
MareKromiumAgo 08, 2008
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20000301.jpgThe "Profile" of 433-Eros (natural colors; credits: Lunexit)54 visiteNEAR takes several images mosaics of 433-Eros daily for purposes of navigating the Spacecraft. The one shown here was taken February 29, 2000, from a range of 289 Km (about 180 miles).
It shows features as small as 30 meters (100 feet) across. All of the mosaics show the same territory over and over, but changes in lighting plus the gradual decrease in the spacecraft's range to the surface are both constantly bringing out new details.
The very oblique illumination in this mosaic is ideal for bringing out small landforms. Many parts of the asteroid have "grooves", such as linear troughs about 100 meters (330 feet) wide and several kilometers long. Similar features have also been observed on other asteroids such as Gaspra, and they are especially numerous on Mars' moon Phobos.
Their origin isn't completely understood, but formation of the grooves probably involves fracturing of the asteroid's subsurface in some way.
(Mosaic of images 0127210446, 0127210510, 0127210574, 0127210656)MareKromiumAgo 08, 2008
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