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| Risultati della ricerca nelle immagini - "Deimos" |
Deimos-HiRISE-090309.jpgDeimos in Natural Colors and HR (credits: NASA/JPL-Caltech and Univ. of Arizona)78 visiteThese color-enhanced views of Deimos, the smaller of the two moons of Mars, result from imaging on Feb. 21, 2009, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.
Deimos has a smooth surface due to a blanket of fragmental rock or regolith, except for the most recent impact craters. It is a dark, reddish object, very similar to Mars' other moon, Phobos. For a comparison, see HiRISE images of Phobos taken on March 23, 2008.
These Deimos images combine HiRISE exposures in Near-InfraRed, Red and Blue-Green wavelengths. In the enhanced color, subtle color variations are visible -- redder in the smoothest areas and less red near the fresh impact craters and over ridges of topographic highs (relative to Deimos' center of gravity). The color variations are probably caused by exposure of surface material to the space environment, which leads to darkening and reddening. Brighter and less-red surface materials have seen less exposure to space due to recent impacts or downslope movement of regolith.
Deimos is about 12 Km (approx. 7,5 miles) in diameter. Its orbital period is 1 day, 6 hours, 17' and 54".
These two images were acquired 5 hours and 35 minutes apart.
The Sun was to the upper left in the first (left) image, and to the right in the second image. The viewing geometry is similar in the two images, but surface features appear very different due to the change in illumination.
With an image scale of about 20 mt (66 feet) per pixel, features 60 mt (197 feet) or larger can be discerned.
These images are products from observations catalogued by the HiRISE team as ESP_012065_9000 and ESP_012068_9000. Other products from these observations are available at http://hirise.lpl.arizona.edu/deimos.php .MareKromium
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Deimos-PIA02699.jpgDeimos, from MRO55 visiteCaption NASA originale:"This image showing the position of the Martian moon Deimos against a background of stars is part of a successful technology demonstration completed by NASA's MRO before arrival at Mars. The spacecraft's Optical Navigation Camera (ONC) was used in February and March 2006 to demonstrate the use of pictures from a small camera for calculating precise location of a Mars-bound spacecraft by comparing the observed positions of Mars' two moons to their predicted positions relative to background stars. While this technique was not necessary for the Mars Reconnaissance Orbiter's own navigation, the demonstration prepares the way for relying on it for navigating precise arrivals for future missions that land on Mars.
This example image from the ONC was taken on March 6, 2006, at a distance of 1,08 MKM (about 671.000 miles) from Deimos. That moon, the smaller of Mars' two, has a diameter of about 15 Km (approx. 9 miles), and orbits 23.459 Km (approx. 14.577 miles) above Mars' surface".
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ESP_012065_9000_COLOR.JPGDeimos (Natural - but enhanced - Colors; credits: NASA/JPL/Univ. of Arizona)76 visiteHiRISE captured this enhanced-color image of Deimos, the smaller of the two moons of Mars, on 21 February 2009.
Deimos has a smooth surface due to a blanket of fragmental rock or regolith, except for the most recent impact craters. It is a dark, reddish object, very similar to Phobos.
There are subtle color variations — redder in the smoothest areas and less red near fresh impact craters and over ridges or topographic highs (relative to its center of gravity).
These color variations are probably caused by the exposure of surface materials to the space environment, which leads to darkening and reddening. Brighter and less-red surface materials have seen less exposure to space due to recent impacts or downslope movement of regolith.
With an image scale of about 20 mt/pixel, features 60 mt or larger can be discerned.MareKromium
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ESP_012068_9000_COLOR5.JPGDeimos (Natural - but enhanced - Colors; credits: NASA/JPL/Univ. of Arizona)53 visiteThis second image of Deimos was acquired 5 h. and 35' after the first one; so the Sun was to the upper left in the first (ESP_01265_9000) image and to the right in this second one (ESP_01268_9000). Although the viewing geometry is similar in the two images, surface features appear very different due to the changes in illumination.
Nota Lunexit: il concetto sancito dagli Amici di Pasadena nell'ultima riga (...Although the viewing geometry is similar in the two images, surface features appear very different due to the changes in illumination...) è ASSOLUTAMENTE FONDAMENTALE per la corretta visione, comprensione ed analisi di quanto mostrato da immagini orbitali o, comunque, ottenute da notevoli distanze rispetto al luogo/rilievo osservato. MareKromium
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Esp_012065_9000_color.jpgDeimos (possible True Colors; credits: Lunar Explorer Italia)57 visitenessun commentoMareKromium
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N-Deimos.jpgDeimos (Natural Colors; credits: NASA/JPL)54 visiteCaption NASA originale:"Color pictures of the two Martian moons have confirmed Earth-based spectra by also showing both satellites to be gray. The Viking imaging data showed the surfaces to be uniformly gray over the complete surface to a resolution of a few hundred meters. No significant color differences were seen on either surface, including areas around craters and those within the bright albedo features on Deimos.
The color indicates composition is of a carbonaceous chondritic material. Deimos, here, is at a range of 2100 km from the Viking 1 Orbiter. In these pictures, color differences have be en exaggerated; most of the color differences are due to noise or are artifacts of the processing, especially around craters and the limb".
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Phobos-400-455-20091201.jpgBig Brother and Little Brother54 visitePhobos and Deimos RAW (left panel) and processed images (right panel).
In a first, ESA’s Mars Express Orbiter imaged the Martian Moons Phobos and Deimos together on November, 5th, 2009.
Apart from their ‘wow’ factor, these unique images will help the HRSC team validate and refine existing orbit models of the two moons.
The images were acquired with the Super Resolution Channel (SRC) of the High Resolution Stereo Camera (HRSC). The camera took 130 images of the moons on November 5th at 09:14 CET in a span of 1,5 minutes at intervals of 1", speeding up to 0,5" intervals toward the end. The image resolution is 110 m/pixel for Phobos and 240 m/pixel for Deimos — Deimos was more than twice as far from the camera.
The Super Resolution Channel of the HRSC uses an additional lens, which has a very narrow field of view of just 0,5°, providing four times the magnification than otherwise providing four times the resolution of the HRSC colour stereo channel.
Phobos, the larger of the two moons, orbits closer to the Red Planet, circling it every 7 hours and 39 minutes. It travels faster relative to Mars than the Moon relative to Earth.
Phobos was about 11.800 Km from Mars Express when the images were taken. Deimos, instead, was about 26.200 Km away.MareKromium
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Phobos_Deimos-PIA10117.jpgCRISM Views Phobos and Deimos53 visiteThese 2 images taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show Mars' 2 small moons, Phobos and Deimos, as seen from the MRO's low orbit around Mars. Both images were taken while the spacecraft was over Mars' night side, with the spacecraft turned off its normal nadir-viewing geometry to glimpse the moons. The image of Phobos, shown at the top, was taken at 01:19 UTC on October 23, 2007 (19:19 EDT on Oct. 22), and shows features as small as 400 mt (1320 feet) across. The image of Deimos, shown at the bottom, was taken at 20:16 UTC (00:16 EDT) on June 7, 2007, and shows features as small as 1,3 Km (0,8 miles) across.
Both CRISM images were taken in 544 colors covering 0.36-3.92 micrometers and are displayed at twice the size in the original data for viewing purposes.
Phobos and Deimos are about 21 and 12 Km (13,0 and 7,5 miles) in diameter and orbit Mars with periods of 7 hours, 39,2 minutes and 1 day, 6 hours, 17,9 minutes respectively. Because Phobos orbits Mars in a shorter time than Mars' 24 hour, 37.4-minute rotational period, to an observer on Mars' surface it would appear to rise in the West and set in the East. From Mars' surface, Phobos appears about one-third the diameter of the Moon from Earth, whereas Deimos appears as a bright star. The moons were discovered in 1877 by the astronomer Asaph Hall, and as satellites of a planet named for the Roman God of War, they were named for Greek mythological figures that personify fear and terror.
The first spacecraft measurements of Phobos and Deimos, from the Mariner 9 and Viking Orbiter spacecraft, showed that both moons have dark surfaces reflecting only 5 to 7% of the sunlight that falls on them. The first reconstruction of the moons' spectrum of reflected sunlight was a difficult compilation from 3 different instruments, and appeared to show a flat, grayish spectrum resembling carbonaceous chondrite meteorites. Carbonaceous chondrites are primitive carbon-containing materials thought to originate in the outer part of the Asteroid Belt. This led to a commonly held view among planetary scientists that Mars' moons are primitive asteroids captured into Martian orbit early in the Planet's history. More recent measurements have shown that the moons are in fact relatively red in their color, and resemble even more primitive D-type asteroids in the outer Solar System.
Those ultra-primitive bodies are also thought to contain carbon as well as water ice, but to have experienced even less geochemical processing than many carbonaceous chondrites.
The version of the CRISM images shown here were constructed by displaying 0.90, 0.70, and 0.50 micrometer wavelengths in the red, green, and blue image planes. This is a broader range of colors than is visible to the human eye, but it accentuates color differences. Both moons are shown with colors scaled in the same way.
Deimos is red-colored like most of Phobos. However, Phobos' surface contains a second material, grayer-colored ejecta from a 9-Km (5,6-mile) diameter crater.
This crater, called Stickney, is located at the upper left limb of Phobos and the grayer-colored ejecta extends toward the lower right.
These CRISM measurements are the first spectral measurements to resolve the disk of Deimos, and the first of this part of Phobos to cover the full wavelength range needed to assess the presence of iron-, water-, and carbon-containing minerals.MareKromium
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Q-viking_1_gallery.pngMoments of Phobos and Deimos108 visitenessun commentoMareKromium
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SOL590-PIA06339_modest.jpgPhobos, Deimos and "The 7 Sisters" - Sol 59054 visiteOriginal caption:"(...) In this view, the Pleiades, a star cluster also known as the "Seven Sisters", is visible in the lower left corner. The bright star Aldebaran and some of the stars in the constellation of Taurus are visible on the right. Spirit acquired this image the evening of Sol 590 (Aug. 30, 2005). The image on the right provides an enhanced-contrast view with annotation.
Within the enhanced halo of light is an insert of an unsaturated view of Phobos taken a few images later in the same sequence (...)".
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SOL590-PIA06340.gifMartian Night - Sol 340 (GIF-Movie)53 visiteTaking advantage of extra solar energy collected during the day, NASA's Mars Exploration Rover Spirit recently settled in for an evening of stargazing, photographing the two moons of Mars as they crossed the night sky. In this view, the Pleiades, a star cluster also known as the "Seven Sisters," is visible in the lower left corner. The bright star Aldebaran and some of the stars in the constellation Taurus are visible on the right. Spirit acquired this image the evening of Sol 590 (such as August, 30th, 2005).
The image on the right provides an enhanced-contrast view with annotation. Within the enhanced halo of light is an insert of an unsaturated view of Phobos taken a few images later in the same sequence.
"It is incredibly cool to be running an observatory on another planet" said planetary scientist Jim Bell of Cornell University, Ithaca, N.Y., lead scientist for the panoramic cameras on Spirit and Opportunity. In this annotated animation, both martian moons, Deimos on the left and Phobos on the right, travel across the night sky in front of the constellation Sagittarius. Part of Sagittarius resembles an upside-down teapot. In this view, Phobos moves toward the handle and Deimos moves toward the lid. Phobos is the brighter object on the right; Deimos is on the left. Each of the stars in Sagittarius is labeled with its formal name. The inset shows an enlarged, enhanced view of Phobos, shaped rather like a potato with a hole near one end. The hole is the large impact creater Stickney, visible on the moon's upper right limb.
On Mars, Phobos would be easily visible to the naked eye at night, but would be only about one-third as large as the full Moon appears from Earth. Astronauts staring at Phobos from the surface of Mars would notice its oblong, potato-like shape and that it moves quickly against the background stars. Phobos takes only 7 hours, 39 minutes to complete one orbit of Mars. That is so fast, relative to the 24-hour-and-39-minute sol on Mars (the length of time it takes for Mars to complete one rotation), that Phobos rises in the West and sets in the East. Earth's moon, by comparison, rises in the East and sets in the West. The smaller martian moon, Deimos, takes 30 hours, 12 minutes to complete one orbit of Mars.
That orbital period is longer than a martian Sol, and so Deimos rises, like most Solar System moons, in the East and sets in the West.
Scientists will use images of the two moons to better map their orbital positions, learn more about their composition and monitor the presence of nighttime clouds or haze. Spirit took the five images that make up this composite with the panoramic camera, using the camera's broadband filter, which was designed specifically for acquiring images under low-light conditions. MareKromium
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SOL594-P_D_Timelapse_594Atxt-A585R1.jpgDeimos and Phobos, from Husband's Hill Summit58 visiteTaking advantage of extra solar energy collected during the day, NASA's Mars Exloration Rover Spirit settled in for an evening of stargazing, photographing the two moons of Mars as they crossed the night sky. Spirit took this succession of images at 150-second intervals from a perch atop "Husband Hill" in Gusev Crater on martian day, or sol, 594 (Sept. 4, 2005), as the faster-moving martian moon Phobos was passing Deimos in the night sky. Phobos is the brighter object on the left and Deimos is the dimmer object on the right. The bright star Aldebaran and some other stars in the constellation Taurus are visible as star trails. Most of the other streaks in the image are the result of cosmic rays lighting up random groups of pixels in the camera.
Scientists will use images of the two moons to better map their orbital positions, learn more about their composition, and monitor the presence of nighttime clouds or haze. Spirit took the five images that make up this composite with its panoramic camera using the camera's broadband filter, which was designed specifically for acquiring images under low-light conditions.
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