The Tharsis Region
MC-9
The Region covers the area from 90° to 135° East longitude and 0° to 30° north latitude on Mars and contains most of the Tharsis Rise. The plateau is about as high as Earth's Mount Everest and about as big in area as all of Europe. Tharsis contains a group of large volcanoes. Olympus Mons is the tallest.
Topographical Map of Tharsis Region
The Tharsis Region contains a group of large volcanoes. Olympus Mons is the tallest. When you enter the Tharsis Region you enter volcano country.
Image of the Tharsis Region
Tharsis is a land of great volcanoes. Olympus Mons is one of the tallest known volcanoes in the Solar System; it is 100 times larger in area than any volcano on Earth. Ascraeus Mons and Pavonis Mons are at least 200 miles across and are over six miles above the plateau that they sit on—and, the plateau is three to four miles above the zero altitude of Mars. Pavonis Mons, the middle in a line of three volcanoes, sits at just about dead center on the equator. Mons is a term used for a large raised feature. Tholus is about the same, but smaller. A Patera is flatter and like a volcano with a super large opening. Actually, a Patera is formed when the top of a volcano collapses because its magma chamber is empty. Several volcanoes form a straight line in the Tharsis Uplift. Two major ones are in the Tharsis Region, they are the Ascraeus Mons and Pavonis Mons. It has been proposed that these are the result of plate motion, which on Earth makes volcanic arc islands. We will start by exploring the biggest volcano of all the Olympus Mons since we left off at its basal scarp in the last Phase.
Olympus Mons
Olympus Mons: (Latin for Mount Olympus) is a large shield volcano on the planet Mars. By one measure, it has a height of nearly 22 km (14 mi). This makes it the tallest mountain on any planet in the Solar System (and, after the 2011 discovery of Rheasilvia Mons on the proto-planet Vesta, the second largest mountain on any world known). It stands almost three times as tall as Mount Everest's height above sea level. Olympus Mons is the youngest of the large volcanoes on Mars, having formed during Mars's Amazonian Period. Astronomers had known Olympus Mons since the late 19th century as the albedo feature Nix Olympica (Latin for "Olympic Snow"). Its mountainous nature was suspected well before space probes confirmed its identity as a mountain. The volcano is located in Mars's western hemisphere at approximately 18.65°N 226.2°E, just off the northwestern edge of the Tharsis bulge. The western portion of the volcano lies in the Amazonis Region (MC-8) and the central and eastern portions in the adjoining Tharsis Region (MC-9). A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from volcanoes that are more explosive. This results in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form. Shield volcanoes contain low viscosity magma giving it flowing mafic lava.
Mons Olympus
As a shield volcano, Olympus Mons resembles in its morphology the large volcanoes making up the Hawaiian Islands. The edifice is about 600 kilometers (370 miles) wide. Because the mountain is so large, with complex structure at its edges, allocating a height to the structure is difficult. It stands 21 km (13 mi) above the Mars global datum, and its local relief, from the foot of the cliffs, which form its margin to the northwest to its peak, is nearly 22 km (14 mi) (a little over twice the height of Mauna Kea as measured from its base on the ocean floor). The total elevation change from the plains of Amazonis Planitia, over 1,000 km (620 mi) to the northwest, to the summit approaches 26 km (16 mi).The summit of the mountain has six nested calderas (collapse craters) forming an irregular depression 60 km (37 mi) × 80 km (50 mi) across and up to 3.2 km (2.0 mi) deep. The volcano's outer edge consists of an escarpment, or cliff, up to 8 km (5.0 mi) tall, a feature unique among the shield volcanoes of Mars. Olympus Mons covers an area approximately the size of Arizona. Being a shield volcano, Olympus Mons has a very low profile. The average slope on the volcano's flanks is only 5°. Slopes are highest near the middle part of the flanks and grow shallower toward the base, giving the flanks a concave upward profile.
Pangboche Crater in the Infrared at the top of Mount Olympus.
Olympus Mons has two craters on its peak. Pangboche Crater is a very fresh, 11-kilometer (6.8 mile) diameter crater near the summit of Olympus Mons. Multiple lines of evidence indicate that Pangboche is geologically young. Olympus Mons is the result of many thousands of highly fluid, basaltic lava flows that poured from volcanic vents over a long period of time. (The Hawaiian Islands exemplify similar shield volcanoes on a smaller scale – see Mauna Kea.) The extraordinary size of Olympus Mons is because Mars lacks mobile tectonic plates ( that is the current theory). Unlike on Earth, the crust of Mars remains fixed over a stationary hotspot, and a volcano can continue to discharge lava until it reaches an enormous height (same current theory). However, this theory could be incorrect as it has been a long time since Mars has seen a volcanic eruption and there seems to be the possibility of plate movement in other areas of Mars.
Rim of Pangboche Crater
Pangboche has a very distinct, sharp rim. Over time, crater rims degrade and blend into their surroundings. It has steep walls as indicated by the numerous boulders rolling down the walls. For boulders and material to dislodge from a slope because of gravity alone, slopes need to be rather steep (approximately 30 degrees). The interior of the crater contains material that likely slumped off the walls during late stages of its formation. The north wall of the crater has material that has not slumped to the floor, instead forming a terrace. Also noteworthy is the abundance of small craters that surround, but do not occur within, Pangboche. These are mostly secondary craters that formed when ejecta from an impact hit the surface. If the small craters were primary craters (formed from an impacter from space), then they would be expected to be within Pangboche as well.
The second crater on Olympus Mons is the 15.6 km (9.7 mi)-diameter Karzok Crater (The two craters are notable for being two of several suspected source areas for shergottites, the most abundant class of Martian meteorites). Roughly, three-quarters of all Martian meteorites can be classified as shergottites. They are named after the Shergotty meteorite, which fell at Shergotty, India in 1865. Shergottites are igneous rocks of mafic to ultramafic lithology. They fall into three main groups, the basaltic, olivine-phyric (such as the Tissint group found in Morocco in 2011) and lherzolitic shergottites, based on their crystal size and mineral content. They can be categorized alternatively into three or four groups based on their rare-earth element content. These two classification systems do not line up with each other, hinting at complex relationships between the various source rocks and magmas that the shergottites formed from.
NWA 6963, a Shergottite found in Morocco, September 2011.
Northeast of Olympus Mons is Cyane Sulci. Northeast of that location is Cyane Fossae.
Cyane Fossae
Fossa (pl. fossae) is a term used in planetary geology to describe a long, narrow depression (trough) on the surface of an extraterrestrial body, such as a planet or moon. The term, which means, "ditch" or "trench" in Latin, is not a geological term as such but a descriptor term used by the United States Geological Survey (USGS) and the International Astronomical Union (IAU) for topographic features whose geology or geomorphology is uncertain due to lack of data or knowledge of the exact processes that formed them. Fossae are believed to be the result of a number of geological processes, such as faulting or subsidence. Many fossae on Mars are probably graben. Grabens are formed by volcanic processes. Cyane Fossae is located at about 235°E and if we go straight south there is another furrowed region which is called Sulci Gordii at about 21°N.
The terraced hills of Sulci Gordii
Many dark streaks are visible here. Research, published in January 2012 in Icarus, found that dark streaks were initiated by air blasts from meteorites traveling at supersonic speeds. The team of scientists was led by Kaylan Burleigh, an undergraduate at the University of Arizona. After counting some 65,000 dark streaks around the impact site of a group of five new craters, patterns emerged. The number of streaks was greatest closer to the impact site. Therefore, the impact somehow probably caused the streaks. In addition, the distribution of the streaks formed a pattern with two wings extending from the impact site. The curved wings resembled scimitars, curved knives. This pattern suggests that an interaction of air blasts from the group of meteorites shook dust loose enough to start dust avalanches that formed the many dark streaks.
Going to 10°N and between 230-235 °E we come to Gigas Sulci.
Gigas Sulci seen as seen by THEMIS.
The wavy linear ridges are dunes. Dark slope streaks are visible on some slopes.
At 10°N 235 °E we come to the Ulysses Fossae.
Mount in the Ulysses Fossae
The Tharsis Region is also home to large troughs (long narrow depressions) called fossae in the geographical language used for Mars. Some of the fossae in this Region are Ulysses Fossae, Olympica Fossae, Ceraunius Fossae, and Tractus Fossae. These troughs form when the crust is stretched until it breaks. The stretching can be due to the large weight of a nearby volcano. Studies have shown that the volcanoes of Tharsis caused most of the major fossae on Mars. The stress that caused the fossae and other tectonic features is centered in Noctis Labyrinthus, at 4 S and 253 E. However, the center has moved somewhat over time. Fossae/pit craters are common near volcanoes in the Tharsis and Elysium system of volcanoes.
At 3°N 235°E, we come Biblis Tholus and right next to it is the Biblis Patera.
THEMIS daytime infrared image mosaic showing the volcano Biblis Tholus in the southern part of the Tharsis region of Mars
Biblis Patera surface topography of Caldera
Next to them ,are another set of volcanoes to the east the Ulysses Tholus and Ulysses Patera. These two are much closer to each other than the first two.
THEMIS daytime infrared image mosaic showing the volcanoes Biblis Ulysses and Ulysses Patera.
Ulysses Patera, with its location in relation to other volcanoes in the area.
Volcanic activity, or volcanism, has played a significant role in the geologic evolution of Mars. Scientists have known since the Mariner 9 mission in 1972 that volcanic features cover large portions of the Martian surface. These features include extensive lava flows, vast lava plains, and the largest known volcanoes in the Solar System. Martian volcanic features range in age from Noachian (>3.7 billion years) to late Amazonian (< 500 million years), indicating that the planet has been volcanically active throughout its history and probably still is so today. Both Earth and Mars are large, differentiated planets built from similar chondritic materials. Many of the same magmatic processes that occur on Earth also occur on Mars, and both planets are similar enough compositionally that the same names can be applied to their igneous rocks and minerals. Volcanism is a process in which magma from a planet’s interior rises through the crust and erupts on the surface. The erupted materials consist of molten rock (lava), hot fragmental debris (tephra or ash), and gases. Volcanism is a principal way that planets release their internal heat. Volcanic eruptions produce distinctive landforms, rock types, and terrains that provide a window on the chemical composition, thermal state, and history of a planet's interior.
Going further east at 5° N 244° E we come to the Pavonis Sulci.
Example of the Pavonis Sulci Region
Just to the east of Pavonis Sulci is the big Volcano Pavonis Mons.
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