Planum Boreum
From Wikipedia, the free encyclopedia
Planum Boreum (Latin: "the northern plain") is the northern polar plain on Mars. It extends northward from roughly 80°N. Surrounding the high polar plain is a flat and featureless lowland plain called Vastitas Borealis which extends for approximately 1500 kilometres southwards, dominating the northern hemisphere. [1] In 1999, the Hubble Space Telescope captured a cyclonic storm in the region. The diameter of the storm was approximately 1750 km and featured an eye 320 kilometres in diameter. [2]
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[edit] Ice cap
Planum Boreum is home to a permanent ice cap comprised mainly of water and carbon dioxide ice. It has a volume of 1.2 million cubic kilometres and covers an area equivalent to about 1.5 times the size of Texas. It has a radius of 600 km. The maximum depth of the cap is 3 km. [3] The spiral patterns in the ice cap were mostly carved by fierce winds and sublimation. [4]
The surface composition of the northern ice cap in middle spring (after a winter's accumulation of seasonal dry ice) has been studied from orbit. The outer edges of the ice cap are contaminated with dust (0.15% by weight) and are comprised mostly of water ice. As one moves toward the pole, the surface water ice content decreases and is replaced by dry ice. The purity of the ice also increases. At the pole, the surface seasonal ice consists of essentially pure dry ice with little dust content and 30 parts per million of water ice. [5]
[edit] Features
The main feature of Planum Boreum is a large canyon called Chasma Boreale. It is up to 100 km wide and features scarps up to 2 km high. [6][7] For a comparison, the Grand Canyon is approximately 1.6 km deep in some places and 446 km long but only up to 24 km wide. Chasma Boreale cuts through polar deposits and ice, such as those present at Greenland.
Planum Boreum interfaces with Vastitas Borealis west of Chasma Boreale at an irregular scarp named Rupes Tenuis. This scarp reaches heights of up to 1 km. At other places, the interface is a collection of mesas and troughs.
Planum Boreum is surrounded by large fields of sand dunes spanning from 75°N to 85°N. These dune fields are named Olympia Undae, Abalos Undae and Hyperboreae Undae. Olympia Undae, by far the largest, covers from 100°E to 240°E. Abalos Undae covers from 261°E to 280°E and Hyperboreale Undae spans from 311°E to 341°E. [8] See also List of extraterrestrial dune fields.
[edit] See also
- Planum Australe, the south polar plain
- Vastitas Borealis
[edit] References
- ^ [1] and [2] give Vastitas Borealis starting at 54.7°N and Planum Boreum at 78.5°N. The radius of Mars is approximately 3400 km, so
- ^ Colossal Cyclone Swirls near Martian North Pole. Retrieved on 2006-11-01.
- ^ LASER PROVIDES FIRST 3-D VIEW OF MARS' NORTH POLE. Retrieved on 2006-11-01.
- ^ Martian 'wobbles' shift climate. BBC News. Retrieved on 2006-11-01.
- ^ Spatial variability and composition of the seasonal north polar cap on Mars. Retrieved on 2006-11-01.
- ^ Fly over the Chasma Boreale at Martian north pole. European Space Agency. Retrieved on 2006-11-01.
- ^ Geologic Map of the Northern Plains of Mars. United States Geological Survey. Retrieved on 2006-01-11.
- ^ USGS Astro: Search Planetary Nomenclature. Retrieved on 2006-11-01.
[edit] External links
- Fly over the Chasma Boreale at Martian north pole - courtesy of Mars Express
- Geologic Map of the Northern Plains of Mars
- HiRISE image of permanent ice mound separated from cap
- Various HiRISE images of the north polar ice cap: [3] [4] [5] [6]
