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MOLA map showing boundaries of Terra Sirenum and other regions
MOLA map showing boundaries of Terra Sirenum near the south pole and other regions

Terra Sirenum is named after the Sirens who were birds with the heads of girls. In the Odyssey these girls captured passing seamen and killed them.[1]

Terra Sirenum is a large region in the southern hemisphere of the planet Mars. It is centered at 39°42′S 150°00′W / 39.7°S 150°W / -39.7; -150 and covers 3900 km at its broadest extent. It covers latitudes 10 to 70 South and longitudes 110 to 180 W.[2] Terra Sirenum is an upland area notable for massive cratering including the large Newton Crater. Terra Sirenum is in the Phaethontis quadrangle and the Memnonia quadrangle of Mars. A low area in Terra Sirenum is believed to have once held a lake that eventually drained through Ma'adim Vallis.[3][4][5]


Chloride depositsEdit

Evidence of deposits of chloride based minerals in Terra Sirenum was discovered by the 2001 Mars Odyssey orbiter's Thermal Emission Imaging System in March 2008. The deposits are approximately 3.5 to 3.9 billion years old. This suggests that near-surface water was widespread in early Martian history, which has implications for the possible existence of Martian life.[6][7] Besides finding chlorides, MRO discovered iron/magnesium smectites which are formed from long exposure in water.[8]

Based on chloride deposits and hydrated phyllosilicates, Alfonso Davila and others believe there is an ancient lakebed in Terra Sirenum that had an area of 30,000 km2 and was 200 meters deep. Other evidence that supports this lake are normal and inverted channels like ones found in the Atacama desert.[9]

Inverted reliefEdit

Some areas of Mars show inverted relief, where features that were once depressions, like streams, are now above the surface. It is believed that materials like large rocks were deposited in low-lying areas. Later, erosion (perhaps wind which can't move large rocks) removed much of the surface layers, but left behind the more resistant deposits. Other ways of making inverted relief might be lava flowing down a stream bed or materials being cemented by minerals dissolved in water. On Earth, materials cemented by silica are highly resistant to all kinds of erosional forces. Examples of inverted channels on Earth are found in the Cedar Mountain Formation near Green River, Utah. Inverted relief in the shape of streams are further evidence of water flowing on the Martian surface in past times.[10]


List of cratersEdit

The following is a list of craters in Terra Sirenum. The crater's central location is of the feature, craters that its central location is in another feature are listed by eastern, western, northern or southern part.

Name Location Quadrangle(s) Diameter Year of approval
Avire 40°49′S 159°46′W / 40.82°S 159.76°W / -40.82; -159.76 Phaethontis 6.85 km 2008
Belyov Phaethontis
Bernard 23°36′S 154°18′W / 23.6°S 154.3°W / -23.6; -154.3 Memnonia 121 km
Bunnik Phaethontis
Burton 14°06′S 156°24′W / 14.1°S 156.4°W / -14.1; -156.4 Memnonia 123 km 1973
Charlier 68°34′S 168°40′W / 68.56°S 168.67°W / -68.56; -168.67 Mare Australe 106.28 km 1973
Clark Phaethontis
Cobres Memnonia
Columbus 29°48′S 166°06′W / 29.8°S 166.1°W / -29.8; -166.1 Memnonia 119 km
Comas Sola 19°35′S 168°31′W / 19.59°S 168.51°W / -19.59; -168.51 Memnonia 120.24 km 1973
Copernicus 48°48′S 168°48′W / 48.8°S 168.8°W / -48.8; -168.8 Phaethontis 300 km 1973
Cross1 Memnonia, Phaethontis
Dechu 42°15′S 157°59′W / 42.25°S 157.99°W / -42.25; -157.99 Phaethontis 22 km 2018
Dejnev 25°30′S 164°48′W / 25.5°S 164.8°W / -25.5; -164.8 Memnonia 152 km 1985
Dunkassa Phaethontis
Ejriksson 19°24′S 173°54′W / 19.4°S 173.9°W / -19.4; -173.9 Memnonia 49 km 1967
Eudoxus 44°54′S 147°30′W / 44.9°S 147.5°W / -44.9; -147.5 Phaethontis 98 km 1973
Galap Phaethontis
Gratteri Memnonia
Henbury Phaethontis
Kamnik Phaethontis
Keeler 61°00′S 151°18′W / 61°S 151.3°W / -61; -151.3 Phaethontis 95 km 1973
Kibuye Memnonia
Koval'sky Memnonia, Phaethontis 297 km 1973
Kuiper 57°24′S 157°18′W / 57.4°S 157.3°W / -57.4; -157.3 Phaethontis 87 km 1973
Langtang Phaethontis
Li Fan 47°12′S 153°12′W / 47.2°S 153.2°W / -47.2; -153.2 Phaethontis 104.8 km 1973
Liu Hsin 53°36′S 171°36′W / 53.6°S 171.6°W / -53.6; -171.6 Phaethontis 137 km 1973
Magelhaens 32°22′S 194°41′W / 32.36°S 194.68°W / -32.36; -194.68 Phaethontis 105 km
Marca Memnonia
Mariner 35°06′S 164°30′W / 35.1°S 164.5°W / -35.1; -164.5 Phaethintis 170 km 1967
Millman Phaethontis
Nansen 50°18′S 140°36′W / 50.3°S 140.6°W / -50.3; -140.6 Phaethontis 81 km 1967
Naruko Phaethontis
Newton 40°48′S 158°06′W / 40.8°S 158.1°W / -40.8; -158.1 Phaethontis 298 km 1973
Niquero Phaethontis
Nordenskiöld Phaethontis
Palikir 41°34′S 158°52′W / 41.57°S 158.86°W / -41.57; -158.86 Phaethontis 15.57 km 2011
Pickering Phaethontis 1973
Ptolemaeus 48°13′S 157°36′W / 48.21°S 157.6°W / -48.21; -157.6 Phaethontis 165 km 1973
Reutov Phaethontis
Selevac Phaethontis
Suess 67°06′S 178°36′W / 67.1°S 178.6°W / -67.1; -178.6 Mare Australe 71.9 km 1973
Sitrah Phaethontis
Taltal Phaethontis
Triolet Phaethontis
Trumpler Phaethontis
Tyutaram Phaethontis 2013
Very 49°36′S 177°06′W / 49.6°S 177.1°W / -49.6; -177.1 Phaethontis 114.8 km 1973
Williams 18°42′S 164°18′W / 18.7°S 164.3°W / -18.7; -164.3 Memnonia 123.2 km 1973
Wright 58°54′S 151°00′W / 58.9°S 151°W / -58.9; -151 Phaethontis 113.7 km 1973
Yaren Phaethontis

Martian gulliesEdit

Terra Sirenum is the location of many Martian gullies that may be due to recent flowing water. Some are found in the Gorgonum Chaos[11][12] and in many craters near the large craters Copernicus and Newton.[13][14] Gullies occur on steep slopes, especially on the walls of craters. Gullies are believed to be relatively young because they have few, if any craters. Moreover, they 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,[15] others have found that the greater number of gullies are found on poleward facing slopes, especially from 30-44 S.[16][17]

Although many ideas have been put forward to explain them,[18] 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.[19][20] 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.[21] 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 layer 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.[22] Aquifers are quite common on Earth. A good example is "Weeping Rock" in Zion National Park Utah.[23]

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.[24][25][26] This ice-rich mantle, a few yards thick, smoothes 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.[27][28][29] Because there are few craters on this mantle, the mantle is relatively young. An excellent view of this mantle is shown below in the picture of the Ptolemaeus Crater Rim, as seen by HiRISE.[30] The ice-rich mantle may be the result of climate changes.[31] Changes in Mars's orbit and tilt cause significant changes in the distribution of water ice from polar regions down to latitudes equivalent to Texas. During certain climate periods water vapor leaves polar ice and enters the atmosphere. The water comes back to ground at lower latitudes as deposits of frost or snow mixed generously with dust. The atmosphere of Mars contains a great deal of fine dust particles. Water vapor will condense on the particles, then fall down to the ground due to the additional weight of the water coating. When Mars is at its greatest tilt or obliquity, up to 2 cm of ice could be removed from the summer ice cap and deposited at midlatitudes. This movement of water could last for several thousand years and create a snow layer of up to around 10 meters thick.[32][33] When ice at the top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulating the remaining ice.[34] Measurements of altitudes and slopes of gullies support the idea that snowpacks or glaciers are associated with gullies. Steeper slopes have more shade which would preserve snow.[16][35] Higher elevations have far fewer gullies because ice would tend to sublimate more in the thin air of the higher altitude.[36]

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.[37] 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.[38][39] 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.[40]

Tongue-shaped glaciersEdit

Possible pingosEdit

The radial and concentric cracks visible here are common when forces penetrate a brittle layer, such as a rock thrown through a glass window. These particular fractures were probably created by something emerging from below the brittle Martian surface. Ice may have accumulated under the surface in a lens shape; thus making these cracked mounds. Ice being less dense than rock, pushed upwards on the surface and generated these spider web-like patterns. A similar process creates similar sized mounds in arctic tundra on Earth. Such features are called “pingos,”, an Inuit word.[41] Pingos would contain pure water ice; thus they could be sources of water for future colonists of Mars.

Concentric crater fillEdit

Concentric crater fill, like lobate debris aprons and lineated valley fill, is believed to be ice-rich.[42] Based on accurate topography measures of height at different points in these craters and calculations of how deep the craters should be based on their diameters, it is thought that the craters are 80% filled with mostly ice.[43][44][45][46] That is, they hold hundreds of meters of material that probably consists of ice with a few tens of meters of surface debris.[47][48] The ice accumulated in the crater from snowfall in previous climates.[49][50][51] Recent modeling suggests that concentric crater fill develops over many cycles in which snow is deposited, then moves into the crater. Once inside the crater shade and dust preserve the snow. The snow changes to ice. The many concentric lines are created by the many cycles of snow accumulation. Generally snow accumulates whenever the axial tilt reaches 35 degrees.[52]

Liu Hsin Crater featuresEdit

Magnetic stripes and plate tectonicsEdit

The Mars Global Surveyor (MGS) discovered magnetic stripes in the crust of Mars, especially in the Phaethontis and Eridania quadrangles (Terra Cimmeria and Terra Sirenum).[53][54] The magnetometer on MGS discovered 100 km wide stripes of magnetized crust running roughly parallel for up to 2000 km. These stripes alternate in polarity with the north magnetic pole of one pointing up from the surface and the north magnetic pole of the next pointing down.[55] When similar stripes were discovered on Earth in the 1960s, they were taken as evidence of plate tectonics. Researchers believe these magnetic stripes on Mars are evidence for a short, early period of plate tectonic activity. When the rocks became solid they retained the magnetism that existed at the time. A magnetic field of a planet is believed to be caused by fluid motions under the surface.[56][57][58] However, there are some differences, between the magnetic stripes on Earth and those on Mars. The Martian stripes are wider, much more strongly magnetized, and do not appear to spread out from a middle crustal spreading zone. Because the area containing the magnetic stripes is about 4 billion years old, it is believed that the global magnetic field probably lasted for only the first few hundred million years of Mars' life, when the temperature of the molten iron in the planet's core might have been high enough to mix it into a magnetic dynamo. There are no magnetic fields near large impact basins like Hellas. The shock of the impact may have erased the remnant magnetization in the rock. So, magnetism produced by early fluid motion in the core would not have existed after the impacts.[59]

When molten rock containing magnetic material, such as hematite (Fe2O3), cools and solidifies in the presence of a magnetic field, it becomes magnetized and takes on the polarity of the background field. This magnetism is lost only if the rock is subsequently heated above a particular temperature (the Curie point which is 770 °C for iron). The magnetism left in rocks is a record of the magnetic field when the rock solidified.[60]

Other featuresEdit

Interactive Mars mapEdit

Acidalia PlanitiaAcidalia PlanitiaAlba MonsAmazonis PlanitiaAonia TerraArabia TerraArcadia PlanitiaArcadia PlanitiaArgyre PlanitiaElysium MonsElysium PlanitiaHellas PlanitiaHesperia PlanumIsidis PlanitiaLucas PlanumLyot (crater)Noachis TerraOlympus MonsPromethei TerraRudaux (crater)Solis PlanumTempe TerraTerra CimmeriaTerra SabaeaTerra SirenumTharsis MontesUtopia PlanitiaValles MarinerisVastitas BorealisVastitas Borealis 
 Interactive imagemap of the global topography of Mars. Hover your mouse to see the names of over 25 prominent geographic features, and click to link to them. Coloring of the base map indicates relative elevations, based on data from the Mars Orbiter Laser Altimeter on NASA's Mars Global Surveyor. Reds and pinks are higher elevation (+3 km to +8 km); yellow is 0 km; greens and blues are lower elevation (down to −8 km). Whites (>+12 km) and browns (>+8 km) are the highest elevations. Axes are latitude and longitude; Poles are not shown.
(See also: Mars Rovers map) (viewdiscuss)

See alsoEdit


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Recommended readingEdit

  • Grotzinger, J. and R. Milliken (eds.). 2012. Sedimentary Geology of Mars. SEPM.
  • Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
  • Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

External linksEdit