| Piú viste - Mars Reconnaissance Orbiter (MRO) |
Q-V-Atmosphere.jpgMars' Atmosphere65 visiteAs part of the checkout of the Mars Reconnaissance Orbiter (MRO) payload after the 10 March 2006 orbit insertion, the Mars Color Imager (MARCI) acquired a seven band color wide angle view of Mars on 24 March 2006. Illustrated here are some of these test images. Note that the linear banding seen in these images are artifacts resulting from incomplete removal of the detector pixel to pixel variations. Such deviations from ground testing calibration are an important reason for taking checkout images.
In the first figure (MARCI2-2a), three views acquired by MRO MARCI are compared to a color composite of two views acquired about 4 hours later by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC). MRO imaging occurred during the early morning on Mars, while the MGS observations were made at around 2 PM local solar time. The region of Mars imaged by MRO on this day was south of the Valles Marineris and includes the large Argyre Basin, its interior plains, Argyre Planitia, and the mountains that comprise the basin rim, Nereidum Montes to the northwest (middle of images) and Charitum Montes to the southeast (bottom of images).
The ultraviolet (UV) image (260 nm in MARCI2-2a) shows how the planet appears in an ozone absorption band. Relatively darker areas in this band normally will indicate the presence of ozone, and relatively lighter areas will indicate the absence of ozone. Water vapor on Mars is anticorrelated with ozone, meaning that lighter areas can be used to track water vapor. The term "relatively" is used here because Mars itself is very dark in the UV owing to absorption of UV light by iron-bearing minerals, and sunlight is deficient in UV relative to visible light, so in general Mars will always look dark in the UV. A second UV band on MARCI (not shown in the figure above) at a longer wavelength allows these differences to be quantified. The MOC wide angle image shows wispy, light water-ice clouds to the northwest of Argyre in the afternoon, but we cannot as yet correlate these clouds with the UV information (especially because the times of day are different). When in its final mapping orbit, MRO will view the same area as MGS separated by only 1 hour, and such correlations will be much more direct.
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PSP_007925_1990_RED_abrowse-01.jpgChannels in Jezero Crater Delta (extra-detail mgnf - MULTISPECTRUM; credits: Lunexit)65 visiteThis extra-detail mgnf shows a section of one channel in greater detail. Wind-blown dunes or ripples now cover much of the channel floor, but in some places the older channel floor is visible. Here, the channel bed has a layered appearance. The plains outside the channel are fractured into polygonal patterns.
The CRISM instrument has detected water-bearing clay minerals in these plains, which were eroded by flows down the channel.
Clays are also seen in the sediments deposited on the floor of Jezero Crater.MareKromium
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PSP_008427_1380_RED_abrowse-02.jpgAutumn in Hellas Basin (edm n. 2 - MULTISPECTRUM-2; credits: Lunexit)65 visitenessun commentoMareKromium
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PSP_007612_2045_RED_abrowse~0.jpgProposed MSL Landing Site in Mawrth Vallis (MULTISPECTRUM; credits: Lunexit)65 visitenessun commentoMareKromium
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PIA10142-SeasonalDryIce~0.jpgTranslucent Seasonal Ice (MULTISPECTRUM; credits: Lunexit)65 visiteIn a Region near the South Pole of Mars, translucent Carbon Dioxide ice covers the ground seasonally. For the first time we can "see" the translucent ice by the affect it has on the appearance of the surface below.
Dark fans of dust from the surface drape over the top of the seasonal ice.
The surface would be the same color as the dust except that the seasonal ice affecting its appearance. Bright bluish streaks are frost that has re-crystallized from the atmosphere.
Sunlight can penetrate through the seasonal layer of translucent ice to warm the ground below. That causes the seasonal ice layer to sublime (evaporate) from the bottom rather than the top. MareKromium
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PSP_009913_1910_RED_abrowse-00.jpgFissures in Cerberus Fossae (natural colors; credits: Lunexit)65 visiteThis image shows an example of “en echelon” fractures in the Cerberus Fossae Region.
These fractures formed tectonically, meaning by the movement of Mars’ crust.
En "echelon" means that the fractures are laterally displaced from each other in a way consistent with the lateral displacement of other fractures in the same area.MareKromium
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PSP_010169_2650_RED_abrowse-00.jpgDunes and other Surface Features in Chasma Boreale (ctx frame - possible True Colors; credits: Lunexit)65 visiteThis image shows dark sand dunes in Chasma Boreale. Chasma Boreale is a giant trough that cuts into the North Polar Ice Cap for about 570 Km (approx. 350 miles) forming a broad valley bordered by stacked layers of ice.
A portion of the North Polar Ice Cap is visible at the northern edge of the trough in the left portion of the image.
Many dark toned sand dunes march down the trough under the winds’ direction.
Coord.: 84,9° North Lat. and 331,8° East Long.
Spacecraft altitude: about 319 Km
M.L.T.: 13:35 (early afternoon)
Solar Incidence Angle: 67°MareKromium
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Psp_009404_2635_red.jpgSmall Crater on the NPLD (possible True Colors; credits: Lunar Explorer Italia)65 visiteMars Local Time: 14:04 (early afternoon)
Coord. (centered): 83,5° North Lat. and 346,8° East Long.
Spacecraft altitude: 317,7 Km (such as about 198,5 miles)
Original image scale range: 31,8 cm/pixel (with 1 x 1 binning) so objects ~95 cm across are resolved
Map projected scale: 25 cm/pixel
Map projection: EQUIRECTANGULAR
Emission Angle: 3,7°
Phase Angle: 57,3°
Solar Incidence Angle: 60° (meaning that the Sun is about 30° above the Local Horizon)
Solar Longitude: 105,2° (Northern Summer)
Credits: NASA/JPL/University of Arizona
Additional process. and coloring: Lunar Explorer ItaliaMareKromium
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PSP_006504_1910_RED_abrowse-00~0.jpgAeolian Features in Arabia Terra (MULTISPECTRUM; credits: Lunexit)65 visiteThis observation shows part of the floor of a large impact crater in Arabia Terra. This crater formed in the distant past when a large asteroid or comet struck Mars, and it has been heavily modified since formation.
The crater was partially filled by sediments, forming the rock outcrops and layers visible in this image.
After this material was laid down, part of the deposits were eroded away. The central part of the image has been carved especially deeply, forming a distinct depression.
This depression has been a site of aeolian transport of sand in more recent times. A particularly interesting aspect of this site is that there appears to have been multiple styles of aeolian activity. Both large sand dunes (the dark hills) and smaller ripples (sharp, light-toned narrow ridges) are visible.
While ripples are often found in association with dunes, the different colors suggest that the material is not the same.
(At full resolution, the surfaces of both the dunes and the large ripples are covered with much smaller ripples)
Even where the ripples and dunes are in contact, there is a distinct contrast between the materials: dark sand appears to fill a trough between two large light ripples, suggesting that the dark sand has moved more recently. This could be due to different grain sizes, since certain sizes are most easily lifted by the wind.MareKromium
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PSP_003326_1800_RED_browse.jpgProposed MSL Landing Site in Eastern Meridiani (possible True Colors; credits: Lunar Explorer Italia)65 visitenessun commentoMareKromium
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PSP_003249_1510_RED_browse_00~0.jpgLayered Deposits in Ritchey Crater (Enhanced Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)65 visiteThis HiRISE image shows eroding layered deposits in Ritchey Crater, a large impact crater in the Southern Highlands.
Three general units can be seen: a relatively dark upper layer, a light middle unit, and the floor material, which may be mostly obscured by dust.
The dark cap layer appears to be relatively hard and resistant, while the light material is weak.
Once the upper layer is removed, the light layer does not last long.
It is unclear how each of these layers formed.
Volcanic ash layers, lake or stream deposits, or sandstone deposited by dunes can all produce horizontal layers. Unraveling the origin would provide important clues to Mars' past.MareKromium
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PSP_007013_1105_RED_abrowse.jpgDunefield in Jeans Crater: Seasonal Monitoring (Natural Colors; credits: Lunar Explorer Italia)65 visitenessun commentoMareKromium
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