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| Ultimi arrivi - A Tribute To Mars Global Surveyor |
Isidis_Planitia.jpgMartian "Cat-paw" print - Isidis Planitia (Original NASA-MGS-MSSS b/w Frame) 63 visiteOriginal caption:"This MGS-MOC image shows a mesa in North-Eastern Isidis Planitia. The mesa might be a remnant of terrain that once more extensively covered the Region".
Location near: 20,3° North and 267,7° West
Image width: ~3 Km (~1,9 mi)
Illumination from: lower left
Season: Northern Winter
Nota: il titolo che abbiamo dato al frame è giustificato dalla formazione craterica visibile sulla mesa la quale ci ricorda, in maniera quasi perfetta, l'impronta di un felino sulla sabbia.Dic 12, 2005
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Volcanic_Features-Collapse_Pit-PIA06416.jpgCollapse Pit in Tractus Fossae (Original NASA/MGS/MSSS b/w Frame)58 visiteOriginal Caption:"This MGS-MOC image shows a 1,5 meters (5 feet) per pixel view of a large Collapse Pit in the Tractus Fossae portion of the Tharsis Region of Mars. Such collapses usually occur along faults formed by expansion and pulling apart of the Planet's Upper Crust".
Location near: 22,5° North Lat. and 101,4° West Long.
Image width: width: ~3 Km (~1,9 mi)
Illumination from: lower left
Season: Northern AutumnOtt 05, 2005
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Craters-Eberswalde_Crater-5-PIA04293_fig3.jpgEberswalde Crater and Delta (Sub-meter-per-pixel cPROTO - detail mgnf)56 visiteOriginal caption:"After the sediments were deposited to form the delta, the material was further buried by other materials - probably sediments - that are no longer present. The entire package of buried material became cemented and hardened to form rock. Later, erosive processes - such as wind - stripped away the overlying rock, re-exposing the delta. Now preserved essentially as a fossil, the former floors of channels in the delta became inverted, to form ridges, by erosion. Channels can be inverted by erosion on both Earth and Mars. Usually this happens when the channel floor, or the material filling the channel, is harder to erode than the surrounding material into which the channel was cut. In some cases, the channels on Earth and Mars have been filled by lava to make them more resistant to erosion. In the case of Eberswalde, there are no lava flows; instead, the channel floors may have been rendered resistant to erosion either by being better-cemented than the surrounding material, or composed of coarser-grained sediment (such as sand and gravel as opposed to silt), or both".Set 21, 2005
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Craters-Eberswalde_Crater-4-PIA04293_fig3.jpgEberswalde Crater and Delta (Sub-meter-per-pixel cPROTO - detail mgnf)56 visiteOriginal caption:"Even with the roll only targeted observation technique, it took more than one Earth year to build up a complete mosaic of images of the delta. In the meantime, the first data showing the deltaic landforms were archived and released to the public and scientific community, long before the MOC Team's analysis and mosaic were complete. Some scientists began independent analyses of the landform at that time. The initial analysis and announcement of the feature was finally published in November 2003.
The Eberswalde delta provides the first clear, 'smoking gun' evidence that some valleys on Mars experienced persistent flow of a liquid with the physical properties of water over an extended period of time, as do rivers on Earth. In addition, because the delta today is "lithified" - that is, hardened to form rock - it provided the first unambiguous evidence that some martian sedimentary rocks were deposited in a liquid (presumably, water) environment. The presence of meandering channels, a cut-off meander, and crisscrossing channels at different elevations (one above the other), provided the clear geologic evidence for these interpretations".Set 21, 2005
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Craters-Eberswalde_Crater-2-PIA04293_fig2.jpgEberswalde Crater and Delta in HR55 visiteOriginal caption:"Additional images from MOC provide some context and show a nearby portion of the fossil delta's inverted channels at a spatial scale of 1,5 mt (about 5 feet) per pixel. The relative positions of these 3 images are indicated in a mosaic image of the entire delta - picture (1). The first MOC narrow angle images of some of the landforms in the delta were acquired in 2000, during the MGS primary mission, but those pictures did not show very well the unambiguous inverted channel forms. Not until the second Earth year of the orbiter's extended mission were the deltaic features recognized in MOC images obtained in March and June of 2002.
Following the initial observations in 2002, the MOC Team began a systematic effort to map the entire Eberswalde Crater delta. Most of this imaging required slewing the whole spacecraft in a technique called "roll only targeted observation" so that it pointed the camera toward the feature. In this way, the camera team was able to build up a mosaic of the delta much more quickly than would have been the case if the team had simply relied upon chance crossing of the delta by the orbiter's usual ground track. This technique was not employed during Mars Global Surveyor's primary mission, except in the search for Mars Polar Lander, but became a routine part of the tool kit during the extended mission".Set 21, 2005
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Craters-Eberswalde_Crater-1-PIA04293_modest.jpgEberswalde Crater and Delta in HR57 visiteOriginal caption:"Scientifically, perhaps the most important result from use of the MOC on NASA's MGS during that spacecraft's extended mission has been the discovery and documentation of a 'fossil delta'. The feature is located in a crater northeast of Holden Crater, near 24,0° South Latitude and 33,7° West Longitude. Since the announcement of the discovery of the delta in November 2003, the International Astronomical Union has provided a provisional name (pending final approval) for the crater in which the landforms occur.
The crater has been named Eberswalde (a German town).
This image offers a HR view of a portion of the fossil delta than any seen earlier. North is up. At the bottom of the frame, the image includes the north end of a looping, inverted, meandering channel. The image covers an area of about 3 by 3 Km (about 1,9x1,9 miles). It was produced using a technique called "compensated pitch and roll targeted observation," in which the rotation rate of the spacecraft is adjusted to match the ground speed under the camera. At full resolution, this map-projected image is at 50 centimeters (20 inches) per pixel".Set 21, 2005
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Volcanoes-Arsia_Mons-03-PIA04294.jpgArsia Mons and its "clouds" (3) - 25 February 2005 (Extremely Saturated Natural Colors; credits NASA/JPL/MSSS)98 visiteOriginal caption:"The spiral dust cloud over Arsia Mons repeats each year, but observations and computer calculations indicate it can only form during a short period of time each year. Similar spiral clouds have not been seen over the other large Tharsis volcanoes, but other types of clouds have been seen. The spiral dust cloud over Arsia Mons can tower 15 to 30 Km (9 to 19 miles) above the volcano. The white and bluish areas in the images are thin clouds of water ice. In the 2005 case, more water ice was present than in the previous years at the time the pictures were obtained. For scale, the caldera of Arsia Mons is about 110 Km (about 68 miles) across, and the summit of the volcano stands about 10 Km (6 miles) above its surrounding plains"Set 21, 2005
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Volcanoes-Arsia_Mons-02-PIA04294_fig2.jpgArsia Mons and its "clouds" (2) - 24 April 2003, Ls 173° (Extremely Saturated Natural Colors; credits NASA/JPL/MSSS)57 visiteOriginal caption:"This image was taken on April 24, 2003, such as in late Southern Autumn on Mars. These pictures prove that some parts of Mars experience weather phenomena that repeat each year, at about the same time. In some Regions, the repeated event may be a dust storm that appears every year, like clockwork, in such a way that we can only wish the weather were so predictable on Earth. One of the repeated weather phenomena occurs each year near the start of Southern Winter over Arsia Mons, which is located near 9° South Latitude, 121° West Longitude. Just before Southern Winter begins, sunlight warms the air on the slopes of the volcano. This air rises, bringing small amounts of dust with it. Eventually, the rising air converges over the volcano's caldera, the large, circular depression at its summit. The fine sediment blown up from the volcano's slopes coalesces into a spiraling cloud of dust that is thick enough to actually observe from orbit".Set 21, 2005
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Volcanoes-Arsia_Mons-01-PIA04294.jpgArsia Mons and its "clouds" (1) - 19 June 2001, Ls 180° (Extremely Saturated Natural Colors; credits NASA/JPL/MSSS)65 visiteVariazioni e ripetitività climatiche osservate sulla Regione dove sorge il grande vulcano Arsia Mons.
Original caption:"A wide angle view taken by the Mars Orbiter Camera on NASA's Mars Global Surveyor. At intervals of approximately one Mars year apart, similar spiral dust clouds over a volcano named Arsia Mons can be seen. This image was taken on June 19, 2001, such as the first day of Southern Winter on Mars".Set 21, 2005
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South_Polar_Features-South_Polar_Cap-PIA04287.jpgThe South Pole of Mars (Original NASA/MGS/MSSS b/ Frame)56 visiteOn 8 September 2005 (UT), the MGS-MOC resumed imaging of Mars after a nearly 2-week hiatus to recover the spacecraft from a glitch that put MGS into a protective "safe mode". The MOC was turned on during MGS orbit 29053, while the spacecraft was flying across day side of the Planet. MOC then resumed taking pictures on the next orbit. Shown here is a portion of the first picture acquired following MOC turn-on. The image shows a view of the Martian South Polar Region, as it appeared on September 8, 2005. The image was taken by MOC's red wide angle camera. In this case, the spacecraft began imaging Mars as it passed across the southern terminator, at the bottom of the image. MGS then flew southward, over the Polar Cap, then northward toward the Equator. The Equatorial Region is further north than the area shown here. The equatorial region is further north than the area shown here. The image not only provided the MOC team a confirmation that MOC imaging has resumed, this particular image, in the map-projected form shown here, is being used by the team to assist in setting the exposures for MOC narrow angle camera images that will be acquired from the south polar region over the next several days.Set 16, 2005
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North_Polar_Features-Cl-louds-Mars_Weather-PIA05079.jpgWeather Patterns over the North Pole of Mars (Natural Colors; credits: NASA/MGS/MSSS)96 visiteMars Global Surveyor entered Mars orbit on 12 September 1997. The 8 Earth Years that MGS has been in orbit span portions of 5 Martian Years. One of the critical science activities that the MOC has been engaged in for the past 8 years has been to document daily changes in the Martian Weather. Each day that MOC is operating, the red and blue wide angle cameras are used to build up a daily global map. These maps provide a record of the Planet's changing meteorological conditions. One important discovery that has been made is that the Red Planet has "repeatable weather patterns". In light of weather-related problems and disruptions that occur every year on Earth, one can only imagine how nice it would be if our planet followed a similar, repeated pattern. The 4 pictures shown here provide an example of one of the weather phenomena that repeat each MY. Each picture shows the North Polar Region of Mars during the Northern Summer Season. Each picture is a composite of several images acquired at different visible wavelengths to give a color view of the planet. Each picture was taken about 1 Mars year apart, and each shows an annular (circular) cloud located over the same terrain each summer.
The first picture, acquired in April 1999, is actually not from the MGS MOC instrument. It was obtained by the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) and was originally released by the Space Telescope Science Institute on 19 May 1999. The reason there is no MOC image for April 1999 is a product of the MGS spacecraft's 8-year history at Mars. MGS was certainly in orbit at the time, and it was taking data during the month of April. However, the camera did not obtain any images between 17 and 28 April because the spacecraft encountered, and then had to be recovered from, a problem. It was at this time that the spacecraft team realized that there is something obstructing the full movement of MGS's high gain antenna. A work-around was created and the mission has continued, ever since, but the down-side was that MOC did not have the opportunity in 1999 to provide detailed observations of the north polar, summertime, annular cloud.
The remaining three pictures show MGS MOC views of the cloud feature, as it appeared in the subsequent 3 Mars years. Each year, the cloud appeared at about the same time or slightly earlier than in the previous year. Despite its superficial resemblance to a hurricane or cyclone on Earth, the northern summer annular cloud does not rotate. The cloud forms as different currents of air merge in the morning hours in the polar region; by afternoon, the annular cloud typically dissipates or breaks up into smaller clouds.
MGS MOC has observed other repeated phenomena over the course of its 8-year mission orbiting Mars. These include dust storms that repeat, year after year, in the same location within a week or two of the time it occurred in the previous year. They also include dust devils in northern Amazonis, which start up shortly after the first day of spring, and keep occurring nearly every afternoon until a few days into the autumn season. MOC is continuing its mission to monitor the planet -- in 2006, MOC's weather observations will be used to provide guidance for the aerobraking maneuvers of the Mars Reconnaissance Orbiter (MRO). MOC images will show whether dust storms are occurring, and whether the dust suspended by these storms will impact the density of the atmosphere at the altitudes that MRO is passing through to slow the spacecraft and change its orbit to the one desired for the MRO primary mission.Set 16, 2005
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Meridiani_Planum-Tepe-2005_09.jpg"Tepe" in Sinus Meridiani (Original NASA/MGS/MSSS b/w Frame)64 visiteOriginal caption:"This MGS-MOC image shows a lonely, light-toned Butte (----> collina "a ceppo") composed of Sedimentary Rock in Northern Sinus Meridiani. The dark landscape that surrounds the Butte was once covered by the same rocks that make up this lonely remnant".
Location near: 2,5° North Lat. and 4,2° West Long.
Image width: ~3 Km (~1,9 mi)
Illumination from: lower left
Season: Northern AutumnSet 14, 2005
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