Cebrenia Region
MC-7
Topographical Map of The Cebrenia Region showing landing site of Viking 2 Lander
The southern and northern borders of the Cebrenia Region are approximately 3,065 km (1,905 mi) and 1,500 km (930 mi) wide, respectively. The north to south distance is about 2,050 km (1,270 mi).
Image of The Cebrenia Region
The Region's prominent features are the large Craters Mie and Stokes, a Volcano, Hecates Tholus, and a group of mountains, Phlegra Montes. This area is a flat, smooth plain for the most part, so the relatively large craters Mie and Stokes really stand out. The Galaxias Region has an area of chaos, where the ground seems to have collapsed.
NASA's Viking Mission to Mars was composed of two spacecraft, Viking 1 and Viking 2, each consisting of an orbiter and a lander. The primary mission objectives were to obtain high resolution images of the Martian surface, characterize the structure and composition of the atmosphere and surface, and search for evidence of life. Viking 2’s orbiter was inserted into a Mars orbit on August 7, 1976 . Imaging of candidate sites was begun and the landing site was selected based on these pictures and the images returned by the Viking 1 Orbiter. The lander separated from the orbiter on September 3, 1976 at 22:37:50 UTC and landed in Utopia Planitia in the Cebrenia Region.
The Surface of Utopia Planitia
Normal operations called for the structure connecting the orbiter and lander (the bioshield) to be ejected after separation, but because of problems with the separation the bioshield it was left attached to the orbiter. The orbit inclination was raised to 75 degrees on 30 September 1976 Viking 2 landed about 200 km west of the crater Mie. Its landing coordinates were 48° N and 226° W.
What would it look like walking around the landing site: The sky would be a light pink. The dirt would also appear pink. The surface would be uneven; the soil would be formed into troughs. Large rocks would be spread about. Most of the rocks are similar in size. Many of the rocks would have small holes or bubbles on their surfaces caused by gas escaping after the rocks came to the surface. Some boulders would show erosion due to the wind. Many rocks would appear to be perched, as if wind removed much of the soil at their bases. In the winter snow or frost would cover most of the ground. There would be many small sand dunes that are still active. The wind speed would typically be 7 meters per second (16 miles per hour).
Viking 2 Lander Image
The soil resembled those produced from the weathering of basaltic lavas. The tested soil contained abundant silicon and iron, along with significant amounts of magnesium, aluminum, sulfur, calcium, and titanium. trace elements, strontium and yttrium were detected. The amount of potassium was 5 times lower than the average for the Earth's crust. Some chemicals in the soil contained sulfur and chlorine that were like typical compounds remaining after the evaporation of sea water.
Photo from Viking Lander 2 shows late-winter frost on the ground on Mars around the lander.
The view is southeast over the top of Lander 2, shows patches of frost around dark rocks. The surface is reddish-brown; the dark rocks vary in size from 10 centimeters (four inches) to 76 centimeters (30 inches) in diameter. This picture was obtained September 25, 1977. The frost deposits were detected for the first time 12 Martian days (sols) earlier in a black-and-white image. Color differences between the white frost and the reddish soil confirm that we are observing frost.
Viking 2 Lander Video
Search for Life: Viking did three experiments to look for life. The results were surprising and interesting. Most scientists now believe that the data were due to inorganic chemical reactions of the soil, although a few scientists still believe the results were due to living reactions. No organic chemicals were found in the soil. However, dry areas of Antarctica do not have detectable organic compounds either, but they have organisms living in the rocks. Mars has almost no ozone layer, like the Earth, so UV light sterilizes the surface and produces highly reactive chemicals such as peroxides that would oxidize any organic chemicals. Research, published in the Journal of Geophysical Research in September 2010, proposed that organic compounds were actually present in the soil analyzed by both Viking 1 and 2.
Just to the east at 48°N and 140°E is the large impact crater Mie.
The Crater Mie Floor
The Crater Mie Floor in color
Impressive research, reported in the journal Science in September 2009, has showed that some new craters on Mars show exposed, pure, water ice. After a time, the ice disappears, evaporating (sublimation) into the atmosphere. The ice is only a few feet deep. The ice was confirmed with the Compact Imaging Spectrometer (CRISM)] on board the Mars Reconnaissance Orbiter (MRO). The ice was found in a total of 5 locations. Three of the locations are in the Cebrenia Region. Impact craters generally have a rim with ejecta around them, in contrast volcanic craters, which usually do not have a rim or ejecta deposits. Sometimes craters will display layers. Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed onto the surface. Therefore, craters can show us what lies deep under the surface.
The Kufra Crater Floor, as seen by HiRISE has pits that are thought to be caused by escaping water. This crater is right on the western border of the Cebrenia Region at 41°N.
Kufra Crater floor, as seen by HiRISE. Pits are thought to be caused by escaping water.
Hrad Valles is an ancient outflow channel in the Cebrenia quadrangle of Mars, located at 38.7° north latitude and 224.7° west longitude. It is 825 km in length and was named for the word for "Mars" in Armenian.
Hrad Valles may have been formed when the large Elysium Mons volcanic complex melted ground ice, as seen by THEMIS.
When hot subsurface molten rock comes close to ice, large amounts of liquid water and mud may have formed. Hrad Valles in the Cebrenia Region is close to Hecates Tholus (the northern-most of the Elysium Volcanoes), and may have supplied water to create the channel. Hrad Valles originates from the volcano region near the southern border of the Cebrenia Region and appears to end near the Kumara Crater at 43°N and 129°E.
Chincoteague Crater is an impact crater in the Cebrenia quadrangle of Mars, located at 41.5° N and 236.0° W. It is 37.0 km in diameter. It is located just to the west of Hrad Valles.
Close up of Chincoteague Crater, as seen by HiRISE. Note the gullies and associated landforms.
Apsus Vallis, as seen by THEMIS.
Apsus Vallis is near the Elysium volcanic system; it may have been partially formed by the action of lava. Apsus Vallis is a channel in the Cebrenia Region of Mars, located at 35.1° north latitude and 225° west longitude. It is 120 km long and was named after a classical river in ancient Macedonia, the present-day Seman River. Apsus Vallis is a small channel originating from the western edge of the volcano region in the south and lies west of Hrad Valles.
Just to the west and northwest of the foothills leading to Hecates Tholus lies the Galaxias Chaos complex. Chaos terrain on Mars is distinctive; nothing on Earth compares to it. Chaos terrain generally consists of irregular groups of large blocks, some tens of kilometers across and a hundred or more meters high. The tilted and flat topped blocks form depressions hundreds of meters deep.
Galaxias Chaos by CTX
A chaotic region can be recognized by a rat's nest of mesas, buttes, and hills, chopped through with valleys which in places look almost patterned. Some parts of this chaotic area have not collapsed completely—they are still formed into large mesas, so they may still contain water ice. Chaos regions formed long ago. In the Galaxias Region the ground seems to have collapsed. Such land forms on Mars are called "Chaos terrain." Galaxias Chaos is different from many other chaotic regions. It does not have associated outflow channels, and it does not display a great elevation difference between it and the surrounding land area, as most of the other chaos regions. Research published in 2010, suggests that the Galaxias Chaos is the site of a volcanic flow that buried an ice-rich layer, called the Vastitas Borealis Formation (VBF).
Galaxias Chaos as seen by HiRISE.
It is generally believed that the VBF is a residue from water-rich materials deposited by large floods. The VBF may have been of varied thickness and may have contained varied amounts of ice. In the thin atmosphere of Mars, this layer would have slowly disappeared by sublimation (changing from a solid directly to a gas).
Galaxias Chaos in the Infrared
Since some areas would have sublimated more than others, the upper lava cap would not be supported evenly and would crack. Cracks/troughs may have begun from sublimation and shrinkage along the edges of the lava cap. Stress from the undermining of the cap edge would have made cracks in the cap. Places with cracks would undergo more sublimation, then the cracks would widen and form the blocky terrain characteristic of regions of chaos.
Next we come to the foothills region leading to the volcano Hecates Tholus located in the southern center of the region. Hecates Tholus is a Martian volcano, notable for results from the European Space Agency's Mars Express mission which indicate a major eruption took place 350 million years ago. The eruption created a caldera 10 km in diameter. It has been suggested that glacial deposits later partly filled the caldera and an adjacent depression. Crater counts indicate this happened as recently as 5 to 20 million years ago. So this is a recent event on the geological time scale.
Hecates Tholus, as seen by Mars Global Surveyor.
However climate models show that ice is not stable at Hecates Tholus today, pointing to climate change since the glaciers were active. It has been shown that the age of the glaciers correspond to a period of increased obliquity of Mars' rotational axis. The volcano is at location 32.12°N 150.24°E, in the Cebrenia Region, and has a diameter of 182 km. It is the northernmost of the Elysium volcanoes; the others are Elysium Mons and Albor Tholus both in the Elysium Region.
Topographical map of Hecates Tholus
Large amounts of water ice are believed to be present under the surface of Mars. Some channels lie near volcanic areas. When hot subsurface molten rock comes close to this ice, large amounts of liquid water and mud may have been formed.
Buvinda Vallis
Buvinda Vallis, as seen by THEMIS. Buvinda Vallis is associated with Hecates Tholus; it lies just east of Hecates Tholus. Located at 33.4 N and 208.1 W. it is 119.6 km long. It was named after a classical river in Hibernia and the present Boyne River, Ireland.
To the east of Hecates Tholus begins the Phlegra Montes It is a system of mountains in the Cebrenia Region of Mars, located at 40.4 degrees north latitude and 163.71 degrees east longitude. Material moving down slope in Phlegra Montes, was seen by HiRISE. The movement is probably aided by water/ice.
The Phlegra Montes
Leaving the Phlegra Montes we move to the northeast and come to Stokes Crater. It is located at 55.9°N 188.8°W and is 66 kilometers in diameter.
Possible Phyllosilicates in Stokes Crater
Megabreccia in the Central Uplift of Stokes Crater
Large craters like Stokes will invariably have a central structural uplift, which form mountain peaks in or near the center of the crater. The Northern plains are largely covered by lavas and sediments, but craters such as Stokes allow us to observe the otherwise buried bedrock, exposed within its central uplift. The first sub image shows a wide variety of colors and textures in a jumbled, fragmental pattern, i.e. "megabreccia." In the stereo anaglyph we can see that many of the fragmental blocks "stick out," indicating that they are more resistant to erosion than the the surrounding finer-grained material between the blocks. There is also an abundance of dark sand dunes and other smaller Aeolian (wind-driven) bed forms on top of the area of exposed bedrock. Megabreccia, consisting of very large fragments of pre-existing bedrock, is created by energetic processes, but especially by impact events on Mars. Although megabreccia deposits can coat central uplifts, it may not have been the Stokes impact that made this megabreccia.
Megabreccia in craters
Going southeast through the Arcadia Planitia which extends back into the Diacria Region. We cross the southeast Corner of the Cebrenia Region at 30°N and 180°E and enter the Amazonis Region.
No comments:
Post a Comment