Our Moon

 

 

 

Our Moon

 

 

Click here for larger image.THE MOON, Earth 's only natural satellite, is unusually large in relation to its planet, having a diameter roughly 1/4 that of Earth 's. Thus, the two bodies are sometimes re f e rred to as a double-planet system. This situation suggests an unusual origin for the Moon. Some proposed origin theories include separation f rom Earth, independent formation, and capture from elsewhere in the solar system. The theory that seems to explain most of our observations, however, is that a Mars-sized body once hit Earth and the resulting debris (from both Earth and the impacting body) accumulated to form the Moon. Whatever the origin, we know the Moon was formed over 4.5 billion years ago (the age of the oldest collected lunar rocks ).

Earth seen from the MoonDuring the Moon's formation, very high temperatures caused extensive melting of its outer layers. The melting resulted in the formation of the lunar crust, probably from a planet-wide "magma ocean." The rocks found on the Moon's highlands are at least 4.5 billion years old, and are rich in light-colored minerals, called feldspar. These rocks, called anorthosites, give the lunar highlands their bright color. In the years since they were form e d , innumerable meteorites have hit the Moon, producing a crust that is intensely cratered and fragmented.

About 4 billion years ago, a series of major impacts occurred , forming huge craters. These craters are now the sites of basins called maria (e.g., Mare Imbrium, Mare Serenitatis). Between 4 and 2.5 billion years ago, volcanic activity filled these basins with dark-colored lavas, called basalts. After this time of volcanism, the Moon cooled down, and has since been relatively inactive, except for the occasional "hits" of meteorites and comets.

Crescent EarthThe Moon has not undergone the continual mountain-building associated with the movement of crustal plates and volcanic activity that characterize Earth; it is a fossil planet on which the earliest stages of geologic evolution are preserved . The Moon, however, is not completely dead. Seismometers emplaced by the Apollo astronauts have recorded small earth quakes (more properly called "moonquakes") at depths of several hundred kilometers. The quakes are probably triggered by tides caused by Earth. Small eruptions of gas from some craters, such as Aristarchus, have also been reported. We know the deep interior of the Moon is still hot, and perhaps partially molten. Although there are local magnetic areas in the lunar crust associated with some craters, there is no planet wide magnetic field; the Moon lacks Earth's molten core .

Our MoonThe Moon's shape is unusual. It is slightly eggshaped, with the small end of the "egg" pointing toward Earth. This position causes the Moon to keep the same face toward Earth at all times. The far side, which cannot be observed from Earth, has days and nights just like those on the near side. The lunar gravity field is also unusual. A surprising discovery from the tracking of the Lunar Orbiter photographic spacecraft in the 1960's revealed strong areas of high gravitational acceleration located over the circular maria. These "mascons" (mass concentrations) are thought to be caused by layers of denser, basaltic lavas that fill the mare basins.

Much remains to be learned about our Moon, beginning with its origin. Active research still continues to yield information about our nearest neighbor in space using the samples and data returned by Apollo and other missions. Speculation has begun on how the Moon might be used to support lunar bases and other human activities in the next century.

 

 

 

Fast Facts

Diameter

3,476 Kilometers

Mass

1/81 the Mass of Earth

Density

3.3 Grams/Cubic Centimeter

Rotation Period

27.3 Days

Surface Gravity

1/6 g

Escape Velocity

2.4 Kilometers/Second

Oldest Rocks

4.5 Billion Years

Atmosphere

None

 

 

Lunar Spacecraft Launch to Moon!

 

 

June 18, 2009 - The Lunar Reconnaissance Orbiter and Lunar Crater Observation and Sensing Satellite are bound for the moon after a flawless liftoff from Cape Canaveral Air Force Station in Florida aboard an Atlas V rocket.  It  is the first spacecraft to be built as part of NASA's return to the Moon.

Click HereThe United States and its partners have begun a program to extend human presence in the solar system, beginning with a return to the Moon. The return to the Moon will enable the pursuit of scientific activities that address our fundamental questions about the history of Earth, the solar system and the universe - and about our place in them. It will allow us to test technologies, systems, flight operations and exploration techniques to reduce the risk and increase the productivity of future missions to Mars and beyond. It will also expand Earth's economic sphere to conduct lunar activities with benefits to life on the home planet.

The Lunar Reconnaissance Orbiter (LRO) is the first step in this endeavor, an unmanned mission to create the comprehensive atlas of the Moon's features and resources necessary to design and build a lunar outpost. LRO follows in the footsteps of the predecessors to the Apollo missions - missions designed in part to search for the best possible landing sites (such as the Ranger, Lunar Orbiter and Surveyor missions). However, building a lunar outpost implies extended periods on the lunar surface and so the goals of LRO go beyond the requirements of these previous missions. LRO focuses on the selection of safe landing sites, identification of lunar resources, and the study of how the lunar radiation environment will affect humans.

 

 

 

The measurements from LRO are uncovering much-needed information about potential landing sites - and much more. Since the 2009 launch, LRO's seven instruments have delivered more than 192 terabytes of data, images and maps to the NASA Planetary Data System - the equivalent of nearly 41,000 typical DVDs. After successfully completing a one-year mission, focused on collecting the datasets required to support future human lunar exploration, LRO is now engaged in a two-year mission focused on addressing important lunar science questions.

 

 

New rock type on the lunar farside found by NLSI Team at Brown/MIT

Published

 

The farside of the Moon has always been a mystery and is only accessible by spacecraft. Marks from Crater Impact Click hereNew compositional information from the Moon Mineralogy Mapper (M3) onboard Chandrayaan-1 has identified a suite of highly unusual rock types exposed at small areas within the farside Moscoviense Basin. M3 is a state-of-the art visible and near-infrared imaging spectrometer that was a guest instrument on Chandrayaan-1, the Indian Space Research Organization’s (ISRO) first mission to the Moon. The instrument is designed to measure accurately the diagnostic mineral absorption bands of solar radiation reflected from the lunar surface.

Five unusual regions exhibited remarkably consistent spectra, all quite different from local lithologies. They can be divided into three distinct rock type groups dominated by the following mafic minerals: (1) orthopyroxene, (2) olivine, and (3) Mg-Al spinel. This family of unusual rock types was designated as OOS. All are highly enriched in the dominant mafic mineral present.

Identified along the innermost Moscoviense Basin ring are several small exposures of three separate but distinctive rock types, the OOS, which contain an exceptionally high concentration of orthopyroxene, olivine, and Mg-rich spinel, respectively. The OOS rocks and developed soil have remained in place undisturbed along the Moscoviense ring since the basin formed.

 
For the Moscoviense Basin, we believe the OOS represent components of the lower crust. The thin to nonexistent crustal thickness estimates for the region suggest that the OOS zone of origin may even approach the crust-mantle interface. The three OOS lithologies are very distinctive and each occurs in more than one location. At the spatial scale of M3 no clear gradients or mixing between OOS are observed. Although the OOS are widely dispersed along the inner ring, we have no direct information about any relationship between the three lithologies. All fade into background material within several pixels. There are cases where each appears completely separately from the others. On the other hand, there are cases where the spinel lithology is spatially close to the orthopyroxene lithology and where the orthopyroxene lithology occurs in close proximity to the olivine lithology, suggesting they may be genetically linked.
 
South Pole Illumination Map Click HereWe propose that the OOS are differentiation products of one or more plutonic events that intruded magmatic material into the lower part of the extensive feldspathic crust, itself derived from the magma ocean. The small size of the OOS (a few kilometers) suggest they could represent several separate small plutonic events or a large cooled plutonic body disrupted by the basin forming event.
 
We are confident of the characterization of the mineral compositions of the OOS. The position of OOS on the innermost ring of the Moscoviense Basin is evidence of their sampling from great depth. Their mineralogy is not consistent with upper crustal anorthositic material sampled by other basins, but rather strongly suggests that the Moscoviense Basin sampled down to lower crustal material. With the exception of the Mg-spinel lithology (which is new), the orthopyroxene- and olivine-rich mineralogy seen in OOS rock types are not unknown on the Moon. But they have never been seen in their actual geologic setting, nor in the concentrations implied by the M3 data for OOS areas. Furthermore, as the remaining M3 data are calibrated, additional outcrops of the Mg-spinel lithology have been also found at one other basin, confirming that this new rock type plays a significant role in lunar crustal structure.
 
This information provides important new insights and constraints on the character and evolution of early planetary crusts. This new compositional information about the lunar crust also opens new avenues of inquiry that are beyond the scope of the discussion presented here. What is the initial composition of melts that are needed to produce the three lithologies? How and when was the melt formed? What materials were melted? Where? How did the mineral separation and concentration occur at the scale observed? What size magma chamber is needed to allow such clear separation of lithologies as a layered intrusive? What depth? What temperature?
These OOS results also provide a taste of major surprises that come from probing and analyzing data acquired by modern sensors orbiting the Moon. We have barely scratched the surface.
 
 
 
 
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