Citizendia
Your Ad Here

Lunar nearside with major maria and craters labeled
Lunar nearside with major maria and craters labeled

The Lunar maria (singular: mare, two syllables) are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Plate tectonics and hotspots Divergent plate boundaries At the They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. This article is about the body of water For other uses see SEA and Seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and hence appear dark to the naked eye. The maria cover about 16 percent of the lunar surface, mostly on the near-side visible from Earth. The few maria on the far-side are much smaller, residing mostly in very large craters where only a small amount of flooding occurred. The traditional nomenclature for the Moon also includes one oceanus (ocean), as well as features with the names lacus (lake), palus (marsh) and sinus (bay). The latter three are smaller than maria, but have the same nature and characteristics.

Contents

Ages

The ages of the mare basalts have been determined both by direct radiometric dating and by the technique of crater counting. Radiometric dating (often called radioactive dating) is a technique used to date materials usually based on a comparison between the observed abundance of a naturally occurring Crater counting refers to a method for estimating the age of a planet's surface The radiometric ages range from about 3. 16 to 4. 2 Ga,[1] whereas the youngest ages determined from crater counting are about 1. 2 Ga (1 Ga = 1 billion years old). [2] Nevertheless, the majority of mare basalts appear to have erupted between about 3 and 3. 5 Ga. The few basaltic eruptions that occurred on the far side are old, whereas the youngest flows are found within Oceanus Procellarum on the nearside. Oceanus Procellarum (oʊˈsiːənəs ˌprɒsəˈlɛərəm Latin for "Ocean of Storms" is a vast Lunar mare on the western edge of the near side of While many of the basalts either erupted within, or flowed into, low lying impact basins, the largest expanse of volcanic units, Oceanus Procellarum, does not correspond to any known impact basin.

Distribution of mare basalts

A global albedo map of the Moon obtained from the Clementine mission. The dark regions are the lunar maria, whereas the lighter regions are the highlands. The image is a cylindrical projection, with longitude increasing left to right from -180 E to 180 E and latitude decreasing from top to bottom from 90 N to 90 S. The center of the image corresponds to the mean sub-Earth point, 0 N and 0 E.
A global albedo map of the Moon obtained from the Clementine mission. Spacecraft design The spacecraft was an octagonal prism 188 m high and 1 The dark regions are the lunar maria, whereas the lighter regions are the highlands. The image is a cylindrical projection, with longitude increasing left to right from -180 E to 180 E and latitude decreasing from top to bottom from 90 N to 90 S. The Mercator projection is a cylindrical map projection presented by the Flemish geographer and cartographer Gerardus Mercator, in 1569 The center of the image corresponds to the mean sub-Earth point, 0 N and 0 E.

There are many common misconceptions concerning the spatial distribution of mare basalts.

  1. Since many mare basalts fill low-lying impact basins, it was once thought that the impact event itself somehow caused the volcanic eruption. Given that mare volcanism typically occurred about 500 million years after the impact, a causal relationship is unlikely.
  2. It is sometimes suggested that the gravity field of the Earth might preferentially allow eruptions to occur on the near side, but not far side. The near side of the Moon is the Lunar hemisphere that is permanently turned towards the Earth, whereas the opposite side is the Far side of the Moon Far Side of the Moon, in original French, La face cachée de la lune, is a 2003 film by Robert Lepage. However, in a reference frame rotating with the Moon, the centrifugal acceleration is exactly equal and opposite to the gravitational acceleration of the Earth. There is thus no net force directed towards the Earth. The Earth tides do act to deform the shape of the Moon, but this shape is one of an elongated ellipsoid with high points at both the sub- and anti-Earth points. As an analogy, one should remember that there are two high tides per day on Earth, and not one.
  3. Since mare basaltic magmas are more dense than upper crustal anorthositic materials, basaltic eruptions might be favored at locations of low elevation where the crust is thin. However, the farside South Pole-Aitken basin contains the lowest elevations of the Moon and is yet only modestly filled by basaltic lavas. The South Pole-Aitken basin is an Impact crater on Earth 's Moon. In addition, the crustal thickness beneath this basin is predicted to be much smaller than beneath Oceanus Procellarum. While crustal thickness might modulate the quantity of basaltic lavas that ultimately reach the surface, crustal thickness by itself can not be the sole factor controlling the distribution of mare basalts. [3]
  4. It is commonly suggested that there is some form of link between the synchronous rotation of the Moon about the Earth, and the mare basalts. In Astronomy, synchronous rotation is a planetological term describing a body orbiting another where the orbiting body takes as long to rotate However, gravitational torques that result in tidal despinning only arise from the moments of inertia of the body (these are directly relatable to the spherical harmonic degree-2 terms of the gravity field), and the mare basalts hardly contribute to this (see also Tidal locking). This article is about the moment of inertia of a rotating object. In Mathematics, the spherical harmonics are the angular portion of an Orthogonal set of solutions to Laplace's equation represented in a system of A separate article treats the phenomenon of Tidal resonance in Oceanography. (Hemispheric structures correspond to spherical harmonic degree-1, and do not contribute to the moments of inertia. ) Furthermore, tidal despinning is predicted to have occurred quickly (on the order to 10s of millions of years), whereas the majority of mare basalts erupted about 1 billion years later.

The reason that the mare basalts are predominantly located on the near-side hemisphere of the Moon is still being debated by the scientific community. Based on data obtained from the Lunar Prospector mission, it appears that a large proportion of the Moon's inventory of heat producing elements (in the form of KREEP) is located within the regions of Oceanus Procellarum and the Imbrium basin, a unique geochemical province now referred to as the Procellarum KREEP Terrane. The Lunar Prospector mission was the third selected by NASA for full development and construction as part of the Discovery Program. KREEP, an Acronym built from the letters K (the atomic symbol for the element Potassium) REE ( '''R'''are '''E'''arth Oceanus Procellarum (oʊˈsiːənəs ˌprɒsəˈlɛərəm Latin for "Ocean of Storms" is a vast Lunar mare on the western edge of the near side of Mare Imbrium, Latin for "Sea of Showers" or "Sea of Rains" is a vast Lunar mare (mahr'-ay filling a basin on Earth 's Moon The Moon is composed of two major geologic provinces that have a unique origin composition and thermal evolution [4][5][6] While the enhancement in heat production within the Procellarum KREEP Terrane is most certainly related to the longevity and intensity of volcanism found there, the mechanism by which KREEP became concentrated within this region is not agreed upon. [7]

Composition

Mare basalts are generally grouped into three series based on their major element chemistry: high-Ti basalts, low-Ti basalts, and very Low-Ti (VLT) basalts. While these groups were once thought to be distinct based on the Apollo samples, global remote sensing data from the Clementine mission now shows that there is a continuum of titanium concentrations between these end members, and that the high-titanium concentrations are the least abundant. Spacecraft design The spacecraft was an octagonal prism 188 m high and 1 TiO2 abundances can reach up to 15 wt. % for mare basalts, whereas most terrestrial basalts have abundances much less than 4 wt. %. Other geochemical subdivisions are based on the abundance of aluminium and potassium.

See also

References

Cited references

  1. ^ James Papike, Grahm Ryder, and Charles Shearer (1998). The geology of the Moon (sometimes called selenology, although the latter term can refer more generally to "lunar This is a list of maria (singular mare) on the Moon. It also includes the one oceanus and the features known by the names lacus Moon Rock is the debut Album by Paul Steel. It was cancelled for release after the album's first single Your Loss failed to chart upon Selenography is the study of the surface and physical features of the Moon. "Lunar Samples". Reviews in Mineralogy and Geochemistry 36: 5. 1-5. 234.  
  2. ^ H. Hiesinger, J. W. Head, U. Wolf, R. Jaumanm, and G. Neukum (2003). "Ages and stratigraphy of mare basalts in Oceanus Procellarum, Mare Numbium, Mare Cognitum, and Mare Insularum". J. Geophys. Res. 108: doi:10. 1029/2002JE001985.  
  3. ^ Mark Wieczorek, Maria Zuber, and Roger Phillips (2001). "The role of magma buoyancy on the eruption of lunar basalts". Earth Planet. Sci. Lett. 185: 71-83.  
  4. ^ Mark Wieczorek and 15 coauthors (2006). "The constitution and structure of the lunar interior". Reviews in Mineralogy and Geochemistry 60: 221-364.  
  5. ^ G. Jeffrey Taylor (August 31, 2000). A New Moon for the Twenty-First Century.
  6. ^ Bradley. Jolliff, Jeffrey Gillis, Larry Haskin, Randy Korotev, and Mark Wieczorek (2000). "Major lunar crustal terranes". J. Geophys. Res. : 4197-4216.  
  7. ^ Charles Shearer and 15 coauthors (2006). "Thermal and magmatic evolution of the Moon". Reviews in Mineralogy and Geochemistry 60: 365-518.  

General references

External links


© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
 Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic