Thursday, November 7, 2013

Small Pale Red Planet Issue 2 Phase 8


The Amenthes Region


This Region contains the eastern part of the Isidis basin, a location where magnesium carbonate was found by MRO. This mineral indicates that water was present and that it was not acidic. Life may have formed in this area.  There are Dark slope streaks, troughs (fossae), and river valleys (Vallis) in this Region.  The Region is named for Amenthes the underworld of Ancient Egypt.


Topographical Map of the Amenthes Region

Some craters in the Amenthes region  show ejecta around them that have lobes. It is believed that the lobed shape is caused by an impact into water or ice saturated ground. Calculations suggest that ice is stable beneath the Martian surface. At the equator the stable layer of ice might lie under as much as 1 kilometer of material, but at higher latitudes the ice may be just a few centimeters below the surface. This was proven when the landing rockets on the Phoenix lander blew away surface dust to reveal an ice surface.


Image of the Amenthes Region

Starting in the northeast corner of the Region we continue exploring in the Utopia Planitia region.  A hard surface crust is formed by solutions of minerals moving up through soil and evaporating at the surface. Some areas of the surface exhibit what is called "scalloped topography,"

Utopia Planitia Scooped and Scalloped Terrain

Here the surface seems to have been carved out by an ice cream scoop. This surface is thought to have formed by the degradation of an ice-rich permafrost.


This photo shows a thin coating of water ice on the rocks and soil in Utopia Planitia

The time the frost appeared corresponds almost exactly with the buildup of frost after one Martian year (23 Earth months). Then it remained on the surface for about 100 days. Scientists believe dust particles in the atmosphere pick up bits of solid water. That combination is not heavy enough to settle to the ground. But carbon dioxide, which makes up 95 percent of the Martian atmosphere, freezes and adheres to the particles and they become heavy enough to sink. Warmed by the Sun, the surface evaporates the carbon dioxide and returns it to the atmosphere, leaving behind the water and dust. The ice seen in this picture, is extremely thin, perhaps no more than one-thousandth of a centimeter thick. The view is looking towards the south southeast.

From here as we go southward from 25°N - 5°N and from 90-100°East we enter the eastern part of the Isidis Planitia.


The northern part of Isidis Planitia in the north of the Amenthes Region at 19°N 97°E.


Crater with Central Peak in the central area of the Isidis Planitia in the Amenthes Region at 14°N 91°E.

A part of the Libya Montes enters the region from the southwest with the Crater Du Martheray in its north center.


Du Martheray Crater lies at the Southern boundary of the Isidis Planitia in the Amenthes Region

Du Martheray Crater is located at 6°N 93°E and is 102 km in diameter.  It was named after Maurice du Martheray (1892 – April 12, 1955)  a Swiss astronomer and poet.

After passing through this area we enter the northern part of Tyrrhena Terra which takes us to the Equator. Tyrrhena Terra is a large area on Mars, centered mostly south of the Martian equator and immediately northeast of the Hellas basin. Its coordinates are  14.8°S 90°E, and it covers an area of 2300 km at its broadest extent.

Valleys in Northern Tyrrhena Terra

Going north from this region we come to the  Amenthes Fossae. It is a trough in the Amenthes Region of Mars located at 9.07 N and 102.68 E. It is 850 km across and was named after the classic albedo feature name of the Region.


Amenthes Fossae Trough - Details of wall of trough, as seen by HI rise, under HI Wish program. Location is 6.7 N and 99.4 E.

Then going east of there we come to the Amenthes Planum which separates the Tyrrhena Terra to the west  from the Terra Cimmeria on the east side. So Amenthes Planum is a plateau that runs between them separating them.  The Amenthes Planum is 960 km in diameter.


Channels along the Eastern Margin of the Amenthes Planum

The Amenthes Fossae has two locations one that is a fissure that goes to the west of Amenthes Planum from about 5-13°N and there is another part of it that appears to the east of Amenthes Planum running  from about 7-14°N.


Central Peak of Crater in Amenthes Fossae Region 9°N 106°E

Going north from there we enter the plains once again, the   Nepenthes Planum.   This area is composed of many small craters.


Isolated Massif in Nepenthes Planum

One of the first craters of note that we come to in this area  is Onon Crater.


Onan Crater

Scale bar is 500 meters long. Location is 16.1 degrees north latitude and 102.5 degrees east longitude. Image was taken by the Mars Reconnaissance Orbiter's HiRISE.  The crater is 3.5 km in diameter and many of the others in the area are of a similar size.  Onan is a Mongolian place name. It is an impact crater but it is almost in a perfect circular shape which means it was probably made in recent history.

The next crater we come to is further north.  Slightly to the northeast at 19°N 105°E is Viana Crater.


Viana Crater (red dot in center)

As I said there are a large number of small craters in this area, Viana is one of the larger ones here.  Viana Crater is 30 km in diameter and was named  after a Brazilian place name.

We now continue northward and enter the Utopia Planitia again which takes us all the way to the northern border of the Amenthes Region.   Heading back south at about 110°E we enter the area of small craters again and come to Marbach Crater at 17°N. We enter the  Amenthes Nepenthes area again.


Marbach Crater (red dot in center)

Marbach Crater is located at  17.8°N 249.0°W.  It is 25.8 km in diameter and is name after a Switzerland place name.

Continuing south as we pass over 10°N we enter Terra Cimmeria.  Terra Cimmeria is a large Martian region, centered at   34.7°S 145°E and covering 5,400 km (3,400 mi) at its broadest extent. It covers latitudes 15 N to 75 S and longitudes 170 to 260 W. Terra Cimmeria is one part of the heavily cratered, southern highland region of the planet. The Spirit rover landed near the area.  A high altitude visual phenomena, probably a condensation cloud, was seen above this region in late March 2012.

Gullies in the Crater Walls in Terra Cimmeria

Terra Cimmeria is the location of gullies that may be due to recent flowing water.  Gullies occur on steep slopes, especially on the walls of craters. Craters are believed to be relatively young because they have few, if any gullies. Moreover, gullies lie on top of sand dunes which themselves are considered to be quite young. Usually, each gully has an alcove, channel, and apron. Some studies have found that gullies occur on slopes that face all directions, others have found that the greater number of gullies are found on pole-ward facing slopes, especially from 30-44 degrees S.  Although many ideas have been put forward to explain them, the most popular involve liquid water coming from an aquifer, from melting at the base of old glaciers, or from the melting of ice in the ground when the climate was warmer.  Because of the good possibility that liquid water was involved with their formation and that they could be very young, scientists are excited. Maybe the gullies are where we should go to find life. There is evidence for all three theories. Most of the gully alcove heads occur at the same level, just as one would expect of an aquifer. Various measurements and calculations show that liquid water could exist in aquifers at the usual depths where gullies begin.  One variation of this model is that rising hot magma could have melted ice in the ground and caused water to flow in aquifers. Aquifers are layers of rock that allow water to flow. They may consist of porous sandstone. The aquifer layer would be perched on top of another layer that prevents water from going down (in geological terms it would be called impermeable). Because water in an aquifer is prevented from going down, the only direction the trapped water can flow is horizontally. Eventually, water could flow out onto the surface when the aquifer reaches a break—like a crater wall. The resulting flow of water could erode the wall to create gullies.  As for the next theory, much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust. This ice-rich mantle, a few yards thick, smoothens the land, but in places it has a bumpy texture, resembling the surface of a basketball. The mantle may be like a glacier and under certain conditions the ice that is mixed in the mantle could melt and flow down the slopes and make gullies.  The third theory might be possible since climate changes may be enough to simply allow ice in the ground to melt and thus form the gullies. During a warmer climate, the first few meters of ground could thaw and produce a "debris flow" similar to those on the dry and cold Greenland east coast. Since the gullies occur on steep slopes only a small decrease of the shear strength of the soil particles is needed to begin the flow. Small amounts of liquid water from melted ground ice could be enough. Calculations show that a third of a mm of runoff can be produced each day for 50 days of each Martian year, even under current conditions.

In Terra Cimmeria on the Equator we come to the Escalante Crater.  So that puts it at 0°on the map.  It is also located partly in the Region to to the south.  But more of it is on the north side than the south side.  It  located between 115-116°E degrees on the Equator.


Escalante Crater Walls

Escalante Crater is an impact crater in the Amenthes Region of Mars. It is located at 0.2° N and 244.7° W. It is 79.3 km (49.3 mi) in diameter, and was named after Mexican astronomer (c. 1930) F. Escalante.

To the northeast of that crater is Ehden Crater.


Central Peak of Ehden Crater

Ehden Crater is located at 8.2°N 241.1°W.  It is 57.7 km in diameter and is named after a Lebanon place name.

Going to the northeast from there we enter the Nepenthes Planum again and then enter another large area called the  Amenthes Cavi.


Cone-Shaped Feature with Summit Pit in Amenthes Cavi.

The Amenthes Cavi area covers an area from 13-17°N and 110-125°E.  Going northeast from there we come to the Hephaestus Fossae.


Hephaestus Fossae -Two Views, as seen by HiRISE. Location is 21.7 degrees north latitude and 122.3 degrees east longitude.

The Hephaestus Fossae are a system of troughs and channels that start in the Cebrenia Region of Mars, then flow south into the Amenthes Region, with a location centered at 21.1 N and 237.5 W. It is 604 km long and was named after a classical albedo feature name. The fossae have been tentatively identified as outflow channels, but their origin and evolution remain ambiguous. It has been proposed that water may have been released into the troughs as a catastrophic flood due to subsurface ice melting following a large bolide impact.

To the east of the Hephaestus Fossae we come to the Hebrus Valles.


Hebrus Valles

The Hebrus Valles: is an ancient system of troughs and valleys in the Amenthes Region of Mars, located at 20.2° north latitude and 233.4° west longitude. It is 317 km long and was named after a river in the Balkans which runs through present day Bulgaria, Greece and Turkey. Some authors have identified the troughs and valleys of Hebrus Valles as outflow channels, but their origin and history remain ambiguous.  Hebrus Valles has tributaries, terraces, and teardrop shaped islands. These features are all characteristic of erosion by fluid flow, but may or may not support the identification of this feature as carved by a single catastrophic outburst flood of water (as the term outflow channel would imply). The tear drop shape of the islands indicate what direction the water used to flow. The terraces may be caused by different layers of rocks or from the water being at different levels.  These features are common for the rivers of the Earth.

Continuing North we go through the Hephaestus Rupes which is also a part of the Utopia Planitia. 


Mesa Near Hephaestus Rupes

This particular Mesa is located at 20°N and 123°E.  Rupes is Latin for cliffs or escarpments so this is the type of terrain we traveling through in this part of the Amenthes Region.

Heading to the northeastern corner of the Region we come the Granicus and Tinjar Vallis in the same area together.  We come to Tinjar Vallis first which is located to the northern border of the Amenthes Region.


Tinjar Vallis

Tinjar Vallis is an ancient outflow channel in the Amenthes Region of Mars, it is located at 38° north latitude and 125.8° east longitude. It is 425 km long and was named after a modern river in Sarawak, Malaysia.  Next as we head east we come to the Granicus Vallis.


The Granicus Vallis

The Granicus Vallis is a valley in the Amenthes Region of Mars, located at 30° north latitude and 129° east longitude. It is 750 km long and is named after the ancient name for river in Turkey. It has been identified as an outflow channel.

Going south along the eastern border of the Amenthes Region we come to the Hyblaeus Fossae.


Hyblaeus Fossae

These fissures are located at 21°N and 137°E.  The diameter of Hyblaeus Fossae is 400 km. and it extends into the next Region to the east it is named after an albedo feature.

The next area we enter is the Hyblaeus Dorsa.  Located from 15-10° N (going southward) and 125°E.  Dorsa in Latin means a hilly or knobby type region.


Sample of Northern Hyblaeus Dorsa

Following this we enter the Elysium Planitia which occupies the southeast corner of the Amenthes Region but also shares it with the Nepenthes Mensae.


Nepenthes Mensae

Between the highlands of Terra Cimmeria and the low plains of Elysium Planitia and Nepenthes Planum lies the rugged region called Nepenthes Mensae. Hills in this region vary in height and the surrounding surface can vary greatly in texture - from dune forms to low ridges to smooth terrain.

The Elysium Planitia, located in the Elysium and Aeolis, and Amenthes Regions,  is a broad plain that straddles the equator of Mars, centered at  3.0°N 154.7°E. It lies to the south of the volcanic province of Elysium, the second largest volcanic region on the planet, after Tharsis.

Crater in the Elysium Planitia

Martian Dust and Dust Storms:


Before and after a Planet-wide Dust Storm

Mars dust storms are much different than the dust devils that many people have seen in images sent back from the planet. On Mars a dust storm can develop in a matter of hours and envelope the entire planet within a few days. After developing, it can take weeks for a dust storm on Mars to completely expend itself. Scientists are still trying to determine why the storms become so large and last so long.  All Mars dust storms are powered by sunshine. Solar heating warms the Martian atmosphere and causes the air to move, lifting dust off the ground. The chance for storms is increased when there are great temperature variations like those seen at the equator during the Martian summer. Because the planet’s atmosphere is only about 1% as dense as Earth’s only the smallest dust grains hang in the air.

Two Dust Devils on Mars

The dust storms were of great concern when probes were first sent to Mars. Early probes happened to arrive in orbit during large events. The Viking missions of 1976 easily withstood two big dust storms without being damaged. They were not the first missions to survive Martian dust storms. In 1971, Mariner 9 arrived at Mars during the biggest dust storm ever recorded. Mission controllers simply waited a few weeks for the storm to subside, then carried on with the mission. The biggest issue that rovers face during a dust storm is the lack of sunlight. Without the light, the rovers have trouble generating enough power to keep their electronics warm enough to function.  Mars dust storms are of great interest to scientists. Even though several spacecraft have observed the storms first hand, scientists are no closer to a definitive answer. For now, the storms on Mars are going to continue to present challenges to planning a human mission to the planet.  According to a NASA report that evaluates the risks of sending a manned mission to Mars, Martian dust poses as one of the biggest potential problems  Compared to here, dust on Mars is thought to be larger and rougher, like the dust that covers the Moon. When Apollo astronauts landed there, they were covered in it in just a few minutes. Within hours, rough lunar dust had scratched up lenses and degraded seals.  While the lunar stays were short, if astronauts make the six-month journey to Mars, they’ll likely be expected to stay a while. That would give potentially hazardous dust plenty of time to accumulate in equipment, cause airlock malfunctions, or even infiltrate astronauts’ lungs.  “Martian dust is a number one risk,” says Jim Garvin, NASA chief scientist at the Goddard Space Flight Center. “We need to understand the dust in designing power systems, space suits and filtration systems. We need to mitigate it, keep it out, figure out how to live with it.”  Dust on Mars doesn’t just sit on the ground – it gets furiously swept about in dust devils and massive dust storms. Thus recently sky watchers could easily spot an 800-mile-wide dust storm as it spun across Mars at 35 mph.

Living with Dust Storms on Mars

Every once and a while, Mars experiences the “perfect dust storm,” where powerful winds kick dust up into the atmosphere where it is spread around until it eventually clouds the entire planet.  One of these rare storms would obviously make it difficult for a spacecraft to land or take off from the planet’s surface, but even smaller storms could be  a substantial mission risk, making atmospheric wind forces the number two mission risk, according to the report.  “We could observe Martian wind speeds at different altitudes, which is vital both for targeting accuracy when a mission lands, and for reaching the right orbit when the mission departs,” said David Beaty, Mars Program Science Manager and the report’s lead author.  Although signs of life haven’t been discovered on Mars, that might be a different story in 25 years. The possibility that microbial organisms, or their remains, could exist in Martian soil is ranked as the number three mission risk.  Having never been exposed to these forms of alien life, they could stand as a substantial health risk to astronauts. The biggest concern to scientists, though, is that these life forms might hitch a ride back to Earth, where they could replicate, prosper, and do unknown damage. Scientists say they need more robotic missions and soil sample returns to truly evaluate this risk. Even a couple pounds of Martian dirt would be of tremendous value, Beaty said.  The same problem was addressed with the Apollo Missions to the Moon when the astronauts were quarantined upon their return.  There should be an easy way to prevent cross-planet contamination through the use of shuttles and space stations should such danger arise.

Dust Chemical Composition Average:

Infrared spectra obtained from the Mariner 9 spacecraft during the 1971–1972 dust storm are used to derive information on the composition and particle size distribution of the dust and to study the time evolution of the storm. The dust is not composed of pure granite, basalt, basaltic glass, obsidian, quartz, andesite, or montmorillonite. The infrared spectra suggest that the dust is a mixture of materials, dominated by igneous silicates with >62;60% SiO2,  or weathering products such as clay minerals, but the dust could possibly have a significant component of lower SiO2 materials such as basalt. Substantial quantities of carbonates, nitrates, or carbon sub-oxide are excluded from the mixture. All infrared, visible, and ultraviolet data on the Martian surface composition seem consistent with a mixture of basalt and clay minerals or high SiO2 igneous rocks, with a surface patina of oxides of iron.

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