| |
| Piú viste - Venus |
Channels-Unnamed_Outflow_Channel-PIA00483.jpgOutflow Channel in South Nawka Vallis (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)57 visiteThis SAR image from the Southern portion of Navka (24,4-25,3° South Latitude and 338,5-340,5° East Longitude) is a mosaic of twelve Magellan orbits that covers approx. 180 Km (about 108 miles) in width and approx. 78 Km (about 47 miles) in length.
In the center of this image are two bright Deposits running North to South.
These Deposits outline an Outflow Channel that flowed from an about 60-Km diameter Crater that is to the South of the Channel itself. Inside the Outflow Channel and outlined by some so-called 'Bathtub Ring' Deposits are small Cones, most likely of volcanic origin.
At the end of the Outflow Channel, where one would expect the smallest particles to be deposited, are specular features which may represent Sand Dunes.
Seasat and space shuttle radar images of sand dunes on Earth also show specular reflections from smooth dune faces that are near-normal to the radar beam.
Other evidence for aeolian activity are the dark and bright Windstreaks running East to West and that formed behind the Cones. Notice how the wind changes direction from a South/East-North/West flow at the right of the image to an East-West flow at the eastern edge of the Outflow Channel.MareKromium
|
|
9-Venus.gifApproaching Venus (GIF anim.)56 visiteOn 20 April 2006, after its first 9-day, elongated orbit around Venus, ESA’s Venus Express started to get closer to the Planet, until it reached its final 24-hour long orbit on 7 May. During this time, and up to today, the spacecraft has been working relentlessly: the new data coming in are already providing first glimpses on planetary features never seen before.
If taking the first ever clear images of the double-eye vortex at Venus’ south pole - imaged by Venus Express during its very first orbit - was already a first in the history of planetary exploration and a very pleasant surprise for the scientists, nobody could expect that the vortex had a structure even more complicated than possibly foreseen.
Infrared images taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board the spacecraft not only provided the first clear view of the vortex, but also gave a much closer insight into it when Venus Express flew over the South Pole at the end of May this year (2006). MareKromium
|
|
Venusian_Atmosphere-VI410_01_23_with_spot_H1.jpgThe Venusian Atmosphere under the Messenger56 visiteCaption ESA:"This grey-scale image, obtained by the VIRTIS instrument on board ESA’s Venus Express, shows the Atmospheric Region of Venus over which NASA’s MESSENGER Spacecraft passed on 5 June 2007. The Region of MESSENGER’s closest approach is in the night side (marked by a circle).
VIRTIS obtained this image at 2,3 micrometres from about 35.000 Km from the Planet, on the night side.
This wavelength makes it possible to probe the atmosphere down to about 30 Km from the surface. Much of the contrast in this image is due to the structure of the lower clouds.
The bright areas correspond to radiation from the lower atmospheric layers, indicating that the clouds are thinner in those areas. At the 2,3-micrometre wavelength it is possible to study not only the morphology of the cloud layers, but also its chemical composition (such as Carbon Monoxide - CO -, Water - H2O -, Sulphur Dioxide - SO2 -, etc)".MareKromium
|
|
Craters-Mona_Lisa_Crater-PCF-LXTT-01.jpgMona Lisa Crater (Natural Colors; credits: Lunar Explorer Italia)56 visitenessun commentoMareKromium
|
|
Ovda_Regio-PIA00218.jpgOvda Regio (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)56 visiteThis Magellan image shows part of the interior of Ovda Regio, one of the large Highlands ringing the Equator of Venus.
Several tectonic events formed this complex block fractured terrain. An underlying fabric of Ridges and Valleys strikes N/E - S/W. These Ridges are spaced approx. 10 to 20 Km (such as about 6 to 12 miles) apart and may have been caused by shortening of the crust at right angles to this trend.
These structures are cut by thoroughgoing extension fractures trending N/W - S/E, suggesting a later episode of N/E - S/W extension. Lastly, the largest Valleys, particularly the about 20 Km (approx. 12 mile) wide one extending across the image, were filled with dark material, probably Lava.
The complex internal fabric of Ovda Regio attests to a long history of tectonic deformation.
This image, centered approx. at 1° South Lat. and 81° East Long., measures approx. 225 Km (about 140 miles) by approx. 150 (about 90 miles) and was acquired by Magellan in November 1990.MareKromium
|
|
Lakshmi_Planum-PIA00249.jpgDanu Montes and Lakshmi Planum (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)56 visiteSouthwest Lakshmi Planum is bounded on the South by the Danu Montes.
Lakshmi Planum is an elevated plateau plain that is bounded on all sides by mountain chains. Here, the Danu Mountains have an angular fractured appearance. Chasms slice diagonally across the mountains in the lower left (South-West) corner of the image. Because of the steep slopes and the local relief of the mountains of several kilometers (2-3 miles, these fault-bounded troughs appear to zig-zag through the mountains when, in fact, they are probably straight if viewed from above.
The radar view provides a perspective that would place the viewer's eye to the right, 27° above the Horizon. Thus, slopes facing to the right can be seen completely, though dark, and slopes facing away to the left appear shortened, often seen only as thin bright lines. In the center of the image is a low volcanic dome (approx. 20 Km - about 12 miles - in diameter).
This type of volcanic feature frequently occurs on the low plains. This dome on the edge of Lakshmi is deformed and faulted where it has been affected by the forces that created the Danu mountains.
The image is approx. 75 Km (about 46 miles) on a side. The center is at 60° North Latitude and 324,5° East Longitude.MareKromium
|
|
Craters-Barton_Crater-PIA00463.jpgBarton Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)56 visiteDuring orbits 404 through 414 on 19-20 September 1990, the Magellan Probe imaged a Peak-Ring Crater that is about 50 Km in diameter located at Latitude 27,4° North and Longitude 337,5° East. The name "Barton" has been proposed by the Magellan Science Team for this Crater, after Clara Barton, founder of the Red Cross; however, the name is tentative pending approval by the International Astronomical Union.
Barton is just at the diameter size that Venus Impact Craters appear to begin to possess Peak-Rings instead of a single Central Peak or Central Peak complex like does about 75% of the craters with diameters between about 50 and 15 Km.
The floor of the Crater is flat and radar-dark, indicating possible infilling by volcanic deposits sometime following the impact event. Barton's Central Peak Ring is discontinuous and appears to have been disrupted or separated during or following the cratering process. The extremely blocky crater deposits (ejecta) surrounding Barton appear to be most extensive on the South-West to South-East (lower left to right) side of it.MareKromium
|
|
Volcanoes-Maat_Mons-PIA00487.jpgVolcanic Domes on the Flank of Maat Mons - East Ovda Region (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)56 visiteThis Magellan image is centered at about 3,2° North Latitude and 194,9° East Longitude, in the Eastern Ovda Region of Venus.
The image, which is approx. 90 Km (about 56 miles) in width and approx. 80 Km (such as about 50 miles) in length, shows some small Volcanic Domes on the Flank of the volcano Maat Mons. The bright flows to the East are most likely rough Lava Flows while the darker flows to the West are probably smoother flows. The dark flows do show some roughness, however, as can be seen by the structure in the flows to the South/West.
These dark flows also have some debris that has been deposited on top of them. The debris may be fine material from the surrounding Plains on top of the flow by wind or it may be ash from the volcano.
Small Volcanic Domes are very common features on the Surface of Venus, indicating that there has been (and maybe there still is) much volcanic activity going on almost everywhere.
Assuming that the central Volcanic Cone is symmetrical in shape and knowing the length of the cone's side and the incidence angle, radar foreshortening yields a height and slope of 688 meters and 8,2°, respectively, for the Cone.
These values are similar to heights and slopes of some Volcanic Cones on the Earth. MareKromium
|
|
Craters-Stephania_Crater-PIA00475.jpgStephania Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)56 visiteCrater Stephania is located at 51,3° Norh Latitude and 333,3° East Longitude in Northern Sedna Planitia.
With a diameter of about 11 Km (6,8 miles), Stephania is one of the smaller Craters on Venus.
Because many small meteoroids disintegrate during their passage through the dense Venusian atmosphere, there is an absence of craters smaller than 3 Km (approx. 1,9 miles) in diameter, and even craters smaller than 25 Km (15,5 miles) are relatively scarce.
The apron of ejected material suggests that the impacting body made contact with the Surface from an oblique angle. Upon closer observation it is possible to delineate secondary craters, impact scars from blocks ejected from the primary crater.
A feature associated with this and many other Venusian Craters is a radar-dark halo.
Since dark radar return signifies a smooth surface, it has been hypothesized that an intense shock wave removed or pulverized previously rough surface material or that a blanket of fine material was deposited during or after the impact.MareKromium
|
|
Volcanoes-Sacajawea_Patera-PIA00485.jpgSacajawea Patera (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)56 visiteThis Magellan image reveals Sacajawea Patera, a large, elongate caldera located in Western Ishtar Terra on the smooth plateau of Lakshmi Planum.
The image is centered at 64,5° North Latitude and 337° East Longitude. It is approximately 420 Km (about 252 miles) wide at the base.
Sacajawea is a depression approximately 1-2 Km (0,6-1,2 miles) deep and abo 120 by 215 Km (approx. 74 by 133 miles) in diameter; it is elongate in a S/W-N/E direction.
The depression is bounded by a zone of circumferential curvilinear structures interpreted to be Graben and Fault Scarps. These structures are spaced 0,5-4 Km (0,3-2,5 miles) apart, are 0,6-4 Km (0,4-2,5 miles) in width and up to 100 Km (approx. 62 miles) in length.
Extending up to approximately 140 Km (about 87 miles) in length from the South/East of the Patera, is a system of linear structures thought to represent a flanking rift zone along which the lateral injection and eruption of magma may have occurred.
A shield edifice of approx. 12 Km (about 7 miles) in diameter with a prominent Central Pit, lies along the trend of one of these features.
The Impact crater Zlata, approx. 6 Km (a little less than 4 miles) in diameter is located within the zone of Graben to the N/W of the Patera.
Few flow features are observed in association with Sacajawea, possibly due to age and state of degradation of the flows.
Mottled bright deposits of about 4 to 20 Km (such as 2,5 up to approx. 12 miles) in width are located near the periphery and in the center of the Patera Floor, within local topographic lows. Diffuse patches of dark material approx. 40 Km (such as about 25 miles) in width are observed S/W of the Patera, superposed on portions of the surrounding Graben.
The formation of Sacajawea is thought to be related to the drainage and collapse of a large Magma Chamber. Gravitational relaxation may have caused the resultant Caldera to sag, producing the numerous Faults and Graben that circumscribe the Patera.
Regions of complex, highly deformed tessera-like terrain are located North and East of the Patera and are seen in the upper portion of the image.MareKromium
|
|
Volcanic_Features-Lava_Flows-PIA00471.jpgLava Flows (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)56 visiteThis is a full resolution mosaic centered at 25° North Latitude and 351° East Longitude.
The Region is approximately 160 Km (100 miles) across. It shows a series of complex Lava Flows which emerge from the Northern Flank of Sif Mons, a large Southern Venusian Volcano.
Several of the Flows occupy narrow troughs formed by long fractures. A sequence of events that can be inferred from this image is the formation of the dark background Plains by eruptions of extremely fluid volcanic material, and the formation of the small Shield Volcanoes on the Plains' Surface that can be seen in the upper left part of the image.
Next, the Region was domed upward probably by heat from the interior of Venus that ultimately caused magmas to break out from the Surface near the Summit Regions forming the Sif volcanic structure and its associated flank eruptions which can be seen in this image.MareKromium
|
|
Venusian_Clouds-Venus_Express-VOI_composit.jpgVenusian cloud structures: day-side and night-side55 visiteThe early infrared image making use of the windows, show complex cloud structures, all revealed by the thermal radiation coming up from different atmospheric depths. In this colour scheme, the brighter the colour (that is, the more radiation comes up from the lower layers), the less cloudy is the observed area.
During capture orbit, preliminary data about the chemical composition of the Venusian atmosphere were also retrieved. Venus’ atmosphere is mainly composed of Carbon Dioxide (CO2). The incoming solar radiation dissociates this molecule into Carbon Monoxide (CO) and Oxygen (O2) in the upper atmospheric layers. In fact, Venus Express has already spotted the presence of an Oxygen airglow high in the atmosphere. However, Venus Express has revealed the presence of Carbon Monoxide as low as the cloud-layer top.
Scientists will continue the data analysis and retrieval to understand the phenomenon, which is very important to clarify the complex chemical processes and cycles at work in the atmosphere of Venus under the influence of solar radiation.
|
|
| 126 immagini su 11 pagina(e) |
|
|
|
|
|
7 | |
|
|
|
|
|
