| Piú votate - Venus |
Craters-Ghost_Crater_in_Lakshmi_Region-PIA00477-PCF-LXTT-IPF.jpgPossible "Ghost Crater" in Lakshmi Region (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)76 visiteThis NASA - Magellan Spacecraft image covers an area of approximately 100 by 120 Km (such as 62,1 by 74,5 miles) and is located in the Lakshmi Region of Venus, at 47° North Latitude and 334° East Longitude. Due to the extremely dense Venusian Atmosphere, primary Impact Craters of less than a 3 Km (such as 1,863 mileS) diameter are, in fact, nonexistent on the Surface of this Planet. However, the Dark Circular Region and the associated Central Bright Feature visible in this frame are reasonably thought to be the remnants of a Meteoroid that was smaller than the size necessary to create an actual Impact Crater but, anyway, that was big enough to leave some scars on the Venusian Surface.
Entering the Venusian Atmosphere at a low velocity (approximately 350 meters/second - such as about 1260 Km per hour) the Central Bright Feature appears to be a Cluster of Small Secondary Impacts, Ejecta and Debris from the original Meteor that broke up in the Atmosphere and, litterally, fell down in pieces. Even though most of the Meteorite did not hit the Surface, the Atmospheric Shock Wave/s that were generated by the Impact Event, could have been great enough to modify the surrounding Region. One explanation for this radar Dark Circular Formation - called "Dark Margin" -, could be that the Shock Wave/s was/were energetic enough to pulverize some portion of the Venusian Surface (remember that smooth surfaces generally appear radar dark).
Another explanation is that the Surface nere, could be blanketed by a fine material that was formed by the original Meteor's break up through the Atmosphere. Just out of curiosity, more than half of the Impact Craters found on Venus have associated "Dark Margins", and most of them are prominently located left of center of the Craters themselves.
This frame (which is an Original NASA - Magellan Spacecraft Radio-Image published on the NASA - Planetary Photojournal with the n. PIA 00477), since it is just a Radio-Image of the Venusian Surface and NOT a real view of it, has been colorized, according to an educated guess carried out by Dr Paolo C. Fienga (LXTT-IPF), in what they could reasonably be its possible Absolute Natural Colors (such as the colors that a human eye would perceive if someone were onboard the NASA - Magellan Spacecraft and, once the thick layer of Venusian Clouds and Fogs is completely overcome, looked down, towards the Surface of Venus itself), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team.MareKromium
(2 voti)
|
|
Venus-Southern_Vortex-ESA-VE.jpgVenus' South Polar Vortex115 visiteCaption NASA:"What's happening over the South Pole of Venus?
To find out, scientists have been studying images taken by the robotic Venus Express spacecraft when it passes over the lower spin axis of Earth's overheated twin. Surprisingly, recent images from Venus Express do not confirm previous sightings of a double storm system there, but rather found a single unusual swirling cloud vortex.
In the above recently released image sequence taken in IR Light and digitally compressed, darker areas correspond to higher temperatures and hence lower regions of Venus' Atmosphere. Also illuminating are recently released movies, which show similarities between Venus' Southern Vortex and the Vortex that swirls over the South Pole of Saturn. Understanding the peculiar dynamics of why, at times, two Eddies (Eddy - plur. Eddies ---> vortice/i, mulinello/i) appear, while at other times a single peculiar Eddy appears, may give insight into how hurricanes evolve on Earth, and remain a topic of research for some time. In three months, the European Venus Express spacecraft will be joined around Venus by the Japanese Akatsuki satellite".MareKromium
(2 voti)
|
|
Craters-Isabella_Crater-PIA00480.jpgIsabella Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)53 visiteCrater Isabella, with a diameter of approx. 175 Km (such as about 108 miles), seen in this MRI (Magellan Radar Image), is the second largest Impact Crater on Venus.
The feature is named in honor of the 15th Century Queen of Spain, Isabella of Castile. Located at 30° South Latitude and 204° East Longitude, the Crater has two extensive flow-like structures extending to the South and to the S/E.
The end of the Southern Flow partially surrounds a pre-existing 40 Km (approx. 25 mile) circular Volcanic Shield.
The South-Eastern Flow shows a complex pattern of Channels and Flow Lobes, and is overlain at its South-Eastern tip by deposits from a later approx. 20 Km (about 12 mile) diameter Impact Crater, Cohn (for Carola Cohn, Australian artist, 1892-1964).
The extensive Flows, unique to Venusian Impact Craters, are a continuing subject of study for a number of Planetary Scientists. It is thought that the Flows may consist of "Impact Melt", suc as rock melted by the intense heat released in the impact explosion. An alternate hypothesis invokes "Debris Flows", which may consist of clouds of hot gases and both melted and solid rock fragments that race across the landscape during the impact event.
That type of Emplacement Process is similar to that which occurs in violent eruptions on Earth, such as the 1991 Mount Pinatubo eruption in the Philippines.MareKromium
(2 voti)
|
|
Craters-Barton_Crater-PIA00463.jpgBarton Crater (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)54 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
(2 voti)
|
|
Ovda_Regio-PIA00218.jpgOvda Regio (possible Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)53 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
(2 voti)
|
|
Venusian_Clouds_Altimetry-2008-04-03438_Figure_3_H.jpgAltimetry of Venus Clouds' Top54 visiteCaption ESA:"A Venus Monitoring Camera UltraViolet image with a superimposed colour mosaic, showing the altitude of the cloud tops.
The colour mosaic was derived from simultaneous pressure measurements by the Visible and Infrared Thermal Imaging Spectrometer".MareKromium
(2 voti)
|
|
Montes-Akna_Montes-PCF-LXTT.jpgAkna Montes (Natural Colors; credits: Lunar Explorer Italia)66 visitenessun commentoMareKromium
(2 voti)
|
|
Craters-Balch_Crater-1.jpgBalch Crater (Natural Colors; credits: Lunar Explorer Italia)53 visitenessun commentoMareKromium
(2 voti)
|
|
Venusian_Clouds-29_VM_Pericentre_mosaic_H.jpgChaotic "Cloud Patterns" at Venus53 visiteCaption ESA:"This mosaic of Venus’ cloud tops was put together with several images obtained by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express. The images where taken in the ultraviolet (365-nanometre wavelength) on 15 August 2006 at distances from 5000 to 1000 Km from the Planet.
The picture clearly shows streaks, wave trains and convection cells. The elongated orbit of Venus Express allows one to zoom into the cloud features as the Spacecraft approaches the Planet. This mosaic shows that mottled and chaotic cloud patterns at low latitudes give way to oriented streaks at about 15° South.
This behaviour indicates transition between two different cloud motion regimes – a ‘dynamic’ regime dominated by local convection where the Sun light hits the Planet perpendicularly (so-called "Sub-Solar Point") - and a more regular, quasi-laminar-flow regime".
MareKromium
(2 voti)
|
|
Venus-PIA10123.jpgApproaching Venus53 visiteCaption NASA:"On Oct. 24, 2006, the MESSENGER Spacecraft came within 2990 Km (such as about 1860 miles) of Venus during its second planetary encounter.
Twenty days before closest approach to Venus the MESSENGER Dual Imaging System snapped pictures of the Planet from a distance of about 16,5 MKM (about 10,3 MMs). Despite the low resolution of the image on the left, one can see that Venus is shrouded in a thick blanket of clouds that hides its surface.
The picture on the right is the same image expanded 4 times, clearly showing the dense Venusian cloud cover".MareKromium
(2 voti)
|
|
Thermal_Map-ORB410_01_surf_comp_H1.jpgThermal Map of Venusian Surface (comparison ESA/NASA)54 visiteCaption ESA:"An unprocessed thermal map of the Venusian Surface obtained by VIRTIS on 5 June 2007 (left) is compared here with a radar image of the same area obtained by NASA’s Magellan Spacecraft in the 1990s (right).
VIRTIS, the imaging spectrometer on board Venus Express, obtained this image at 1 micrometre, a wavelength that allows detection of radiation originating from the surface. The imaged region is that which NASA’s MESSENGER flew over as it made its closest approach to the Planet.
Magellan’s radar imaging and altimetry maps made it possible to measure the elevation and the radio-optical properties of the surface. Venus Express’ VIRTIS is providing the first complete set of thermal maps of the surface of Venus.
Correlations between topographic and thermal data similar to the ones shown in this image-composite will allow the scientists to understand if the measured temperature of the surface depends only on the altitude – where higher altitudes simply corresponds to colder, temperatures such as on Earth – or if it depends on the presence of previously undetected sources of heat such as active volcanoes".MareKromium
(2 voti)
|
|
South_Polar_Regions-0.gifVenusian South Polar Vortex through Venus Express (1)53 visiteThis composite video sequence was obtained by the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board ESA’s Venus Express.
The single images were taken from 7 to 11 April 2007 over 5 different orbits. In each orbit the images were collected over a time span of 8 hours and were separated by about half an hour. The average distance from the Planet was about 65.000 Km.
The Latitude of the observed area spans 50 to 90° South. The Longitude spans about 20 to 150° East.
The video shows details of the Planet’s South Pole in RGB colour. The data obtained at 1.7 microns is shown in blue, while those obtained at 3.8 microns is represented in red.
Using specific wavelengths (3.8 and 1.7 microns, respectively), the observations allowed the imaging of the day and night areas around the South Pole simultaneously, at different depths (at about 65 Km and below the cloud deck, respectively) simultaneously. The intersection between the polar atmospheric structures seen at different wavelengths is visible well, due to the optical properties of the clouds.
MareKromium
(2 voti)
|
|
| 126 immagini su 11 pagina(e) |
 |
|
|
|
|
|
8 | |
|
|
