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For some time, scientists have thought that the location of the poles of Mars shifted due to the great mass of volcanic material in the
For some time, scientists have thought that the location of the poles of Mars shifted due to the great mass of volcanic material in the Tharsis
Tharsis () is a vast volcanic plateau centered near the equator in the western hemisphere of Mars. The region is home to the largest volcanoes in the Solar System, including the three enormous shield volcanoes Arsia Mons, Pavonis Mons, and Asc ...
dome which includes Olympus Mons
Olympus Mons (; Latin for Mount Olympus) is a large shield volcano on Mars. The volcano has a height of over 21.9 km (13.6 mi or 72,000 ft) as measured by the Mars Orbiter Laser Altimeter (MOLA). Olympus Mons is about two and a h ...
, the highest volcano in the Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
. For a period early in the history of Mars, the poles were about 20 degrees away from their present geographic positions. At that time ice was deposited in a region called Dorsa Argentea Formation The Dorsa Argentea Formation (DAF) is thought to be a large system of eskers that were under an ancient ice cap in the south polar region of Mars. The ancient ice cap was at least twice the size of the present ice cap and may have been 1500–2000 ...
. Also, the Martian dichotomy
The most conspicuous feature of Mars is a sharp contrast, known as the Martian dichotomy, between the Southern and the Northern hemispheres. The two hemispheres' geography differ in elevation by 1 to 3 km. The average thickness of the Marti ...
was aligned along the equator. A band of rivers formed at around 25 degrees south carried water from the southern highlands to the northern lowlands. After the polar shift, the location of the dichotomy boundary and the band of river valleys shifted. Dorsa Argentea was no longer at the pole. To produce the change in the pole location, the tilt of the planet remained unchanged, rather the crust and mantle moved. They rotated around the core.
This study suggests that the volcanoes and the movement of the poles occurred at about the same time. Volcanoes were erupting when the rivers were flowing with water. Perhaps the volcanoes supplied much water to the atmosphere, as well as carbon dioxide to warm the atmosphere; these effects would provide water for the rivers.
Tharsis is found in the Amazonis quadrangle
The Amazonis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Amazonis quadrangle is also referred to as MC-8 (Mars Chart-8).
The quadrangle cove ...
and the Tharsis quadrangle
The Tharsis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Tharsis quadrangle is also referred to as MC-9 (Mars Chart-9).
The name Tharsis refe ...
.
See also
*True polar wander
True polar wander is a solid-body rotation of a planet or moon with respect to its spin axis, causing the geographic locations of the north and south poles to change, or "wander". Unless the body is totally rigid (which the Earth is not) its sta ...
*Geography of Mars
Areography, also known as the geography of Mars, is a subfield of planetary science that entails the delineation and characterization of regions on Mars. Areography is mainly focused on what is called physical geography on Earth; that is the di ...
*Geology of Mars
The geology of Mars is the scientific study of the surface, crust, and interior of the planet Mars. It emphasizes the composition, structure, history, and physical processes that shape the planet. It is analogous to the field of terrestrial geo ...
*Volcanism on Mars
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 in ...
References
{{Mars Geology of Mars