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| Risultati della ricerca nelle immagini - "Callisto" |
Callisto-Asgard emi.-Gal-PIA00562_modest.jpgThe "Asgard" hemisphere of Callisto (detail mgnf)54 visiteCaption NASA originale:"...Dominating the scene is the impact structure, Asgard, centered on the smooth, bright region near the middle of the picture and surrounded by concentric rings up to 1.700 kilometers in diameter. A second ringed structure with a diameter of about 500 kilometers can be seen to the north of Asgard, partially obscured by the more recent, bright-rayed crater, Burr. The icy materials excavated by the younger craters contrast sharply with the darker and redder coatings on older surfaces of this Moon..."
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Callisto-Asgard emisph.-Gal-PIA01100_modest.jpgThe "Asgard" hemisphere of Callisto53 visiteCaption NASA originale:"False color view of a portion of the leading hemisphere of Jupiter's moon Callisto as seen through the infrared filters of the Solid State Imaging (CCD) system aboard NASA's Galileo spacecraft. North is to the top of the picture and the sun illuminates the surface from the east. More recent impacts have excavated bright, relatively clean ice from beneath Callisto's battered surface. Callisto's dark mottled appearance may be due to contamination by non-ice components contributed by impactors or concentrated in a residue as ice is removed".
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Callisto-Chain of craters-PIA00514_modest.jpgA chain of craters on Callisto95 visiteCaption NASA originale:"A portion of a chain of impact craters on Jupiter's moon Callisto is seen in this image taken by the Galileo spacecraft on November 4, 1996. This crater chain on Callisto is believed to result from the impact of a split object, similar to the fragments of Comet Shoemaker-Levy 9 which smashed into Jupiter's atmosphere in July of 1994".
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Callisto-HR-00.jpgCallisto: the full disk (HR)53 visitenessun commento
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Callisto-HR-01.jpgCallisto: North Pole and Northern Hemisphere (HR) - detail mgnf115 visitenessun commento
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Callisto-HR-02.jpgCallisto: South Pole and Southern Hemisphere (HR) - detail mgnf53 visitenessun commento
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Callisto-PIA00080-PCF-LXTT-IPF.jpgClosing-up on Valhalla (Absokute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)67 visiteCallisto was revealed by the NASA - Voyager 1 cameras to be a heavily cratered and - most likely (as it was thought at that time) - geologically inactive Celestial Body. This mosaic of Voyager 1 images, obtained at a distance of about 400,000 Km (about 248.000 miles) from Callisto, shows Surface details as small as 10 Km (such as 6,2 miles) across. The largest Impact Features on the Callistoan Surface are the so-called "Multi-Ring Impact Basins"; two of them are enormous and Valhalla - the prominent Impact Feature visible here, in today's APOD - is the largest one, with a Bright Central Region approx. 600 Km (a little more than 372 miles) in diameter, and Rings extending as far as about 1800 Km (approx. 1118 miles) from the center. The second largest Impact Multi-Ring Basin is named Asgard, and it measures about 1600 Km (a little more than 993 miles) in diameter.
Multi-Ring Impact Structures probably originated as a result of a Post-Impact Concentric Fracturing of the Lithosphere lying on a layer of soft or - maybe - even Liquid Material: possibly, an Ocean. Last, but not least, in our opinion, as IPF, the remarkable resemblances existing between the Callistoan Valhalla Crater and the Tyre Crater, located on the other Jovian moon Europa, (*) may tell us, in the end, VERY similar stories about these two mysterious Celestial Bodies. Stories that may talk about worlds that, certainly a long, long time ago, were completely (or almost completely) covered by water. Stories that should also tell us something about what could still be happening, even now, up there: in the depths of Callisto, Europa and, maybe, of a few other Celestial Objects orbiting around the four Gas-Giant Planets of the Solar System...
(*) note: if you want to take a look at Tyre Crater, please refer to the APOD of January, 29, 2013
The Catenae, on the other hand (for example the Gomul Catena), are long Chains of Impact Craters lined up in straight lines across the Surface of Callisto. They were probably created by objects that were tidally disrupted as they passed close to Jupiter prior to the impact on Callisto, or by very oblique Impacts.
This frame (which is an Original NASA - Voyager 1 Spacecraft false color image mosaic published on the NASA - Planetary Photojournal with the ID n. PIA 00080) has been additionally processed and then re-colorized, according to an educated guess, by Dr Paolo C. Fienga (LXTT-IPF), in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Voyager 1 Spacecraft and then looked outside, towards the Jovian moon Callisto), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among others, the existence of different Elements present on the Surface of Callisto, each having a different Albedo (---> Reflectivity) and Chemical Composition.MareKromium
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Callisto-PIA02277-PCF-LXTT-IPF.jpgValhalla! (Absokute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)73 visiteThis picture of the gigantic Multi-Ring Impact Basin named "Valhalla" and located on the Jovian moon Callisto, was taken by the NASA - Voyager 1 Spacecraft in the morning of March 6, of the AD 1979, at a distance of about 200.000 Km (such as approx. 124.000 miles) from the Surface of the farthermost of the 4 (four) so-called "Galilean" Natural Satellites (or moons) of the Gas-Giant Planet Jupiter. The complicated Circular Structure which characterizes Valhalla is, in a way (and according to NASA), relatively similar to other large Circular Impact Basins that can be seen on the Surface of the Earth's Moon as well as on the Planet Mercury but, as we already wrote and underlined in the past, we, as IPF, do believe that a true and strong resemblance between Valhalla and another Multi-Ring Impact Basin can only be found with the huge Tyre Crater; a Multi-Ring Impact Crater that is located, as you know, on the Jovian moon Europa.
Usually, the inner portions of these Multi-Ring Impact Basins are generally surrounded by Radially Lineated Ejecta and several Concentric Mountainous Ring Structures, which are thought to have formed during the Impact Event itself. However, the Callistoan Valhalla Multi-Ring Impact Basin consists of a Light-Floored Central Basin, that is approx. 300 Km (such as a little more than 186 miles) in diameter, surrounded by at least 8 (eight) to 10 (ten) discontinuous and rhythmically spaced Ridges, but no Radially Lineated Ejecta can be seen. In any case, the great number of Rings observed around Valhalla is a fact which is consistent with the hypothesis that Callisto possesses a very low Planetary Density and, also, a low internal strength. Furthermore, if you look carefully on the upper right side of the frame, at about 2 o'clock, a beautiful and extremely long and regular Catena (---> Chain of Craters, probably originated by a Cometary Strike or a Meteor that was heavily fragmented at the time of the Impact) can be seen.
This frame (which is an Original NASA - Voyager 1 Spacecraft b/w image published on the NASA - Planetary Photojournal with the ID n. PIA 02277) has been additionally processed and then colorized, according to an educated guess, by Dr Paolo C. Fienga (LXTT-IPF), in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Voyager 1 Spacecraft and then looked outside, towards the Jovian moon Callisto), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among others, the existence of different Elements present on the Surface of Callisto, each having a different Albedo (---> Reflectivity) and Chemical Composition.MareKromium
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Callisto-PIA03456-PCF-LXTT-IPF.jpgApproaching Callisto (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)71 visiteBright scars on a darker Surface testify to a long history of impacts on the Jovian moon Callisto, as it can be seen in this image obtained by the NASA - Galileo Spacecraft. The picture, taken in May 2001, is the only complete global Absolute Natural Color image of Callisto ever obtained by the NASA - Galileo Spacecraft, which orbited around Jupiter from December, 7, of the AD 1995 and until September 21, of the AD 2003, when the Spacecraft was destroyed during a controlled impact with Jupiter itself.
Of Jupiter's 4 (four) largest moons (also known as the "Galilean Moons"), Callisto orbits farthest from the Giant Gas Planet. Furthermore, Callisto's Surface is uniformly cratered but, as you can see for yourself, is not uniform in color or brightness at all. At present day, Planetary Scientists believe that the brighter areas are mainly Ice while the darker ones should be made of highly eroded (and Ice-poor) Rocky Materials.
This frame (which is an Original NASA - Galileo Spacecraft color frame published on the NASA - Planetary Photojournal with the ID n. PIA 03456) has been additionally processed and then re-colorized, according to an educated guess, by Dr Paolo C. Fienga (LXTT-IPF), in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Galileo Spacecraft and then looked outside, towards the Jovian moon Callisto), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among others, the existence of different Elements present on the Surface of Callisto, each having a different Albedo (---> Reflectivity) and Chemical Composition.MareKromium
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Callisto-V1-PIA00362_modest.jpgCallisto from 1.200.000 Km (Voyager 1)53 visiteCaption NASA originale:"This color photo of Jupiter's satellite Callisto was made from three black-and-white images taken March 5 from a distance of 746.000 miles (1,2 MKMs).
It shows the entire hemisphere of Callisto that was photographed at HR by Voyager 1 during the close encounter with the satellite. Visible near the upper left limb is the large basin-like structure discovered by Voyager 1. The central region of the basin is much brighter than the average surface of the satellite. Near the south polar region are two bright areas associated with smaller basin-like structures. These bright areas are believed to contain more clean ice than the rest of Callisto's generally 'dirty-ice' surface".
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Callisto-V1-PIA02277_modest.jpgCallisto's basin from Voyager 153 visiteCaption NASA originale:"This picture of a multi=ring basin on Callisto was taken the morning of March 6, 1979, from a distance of about 200.000 Km. The complicated circular structure seen at left center is similar to the large circular impact basins that dominate the surface of the Earth's moon and also the planet Mercury. The inner parts of these basins are generally surrounded by radially lineated ejecta and several concentric mountainous ring structures that are thought to form during the impact event. This multi-ring basin on Callisto consists of light floored central basin some 300 k m in diameter surrounded by at least eight to ten discontinuous rhythmically spaced ridges. No radially lineated ejecta can be seen. The ring structures on Moon and Mercury have been likened to ripples produced on a pond by a rock striking the water. The great number of rings observed around this basin on Callisto is consistent with its low planetary density and probable low internal strength".
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Callisto-full disk-PIA03456_modest.jpgCallisto from Galileo87 visiteCaption NASA originale:"Bright scars on a darker surface testify to a long history of impacts on Jupiter's moon Callisto in this image of Callisto from NASA's Galileo spacecraft.
The picture, taken in May 2001, is the only complete global color image of Callisto obtained by Galileo, which has been orbiting Jupiter since December 1995. Of Jupiter's four largest moons, Callisto orbits farthest from the giant planet.
Callisto's surface is uniformly cratered but is not uniform in color or brightness. Scientists believe the brighter areas are mainly ice and the darker areas are highly eroded, ice-poor material".
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