வெள்ளி, டிசம்பர் 26, 2008

Chandrayaan reveals changes in rock composition on Moon

BANGALORE: Chandrayaan-1 India's first Moon mission has confirmed the presence of iron in the lunar soil and, for the first time, revealed changes in rock and mineral composition. The sighting of the mineral is the first in the past five years and only the second in 10 years following a US mission in 1998-99 and European mission in 2003. 

"Obviously many missions before have found iron, but Chandrayaan-1 has reiterated the presence. We believe it is very significant because the mission has already fulfilled one of its objectives, which was to sight minerals. More is to come and it should be exciting if we can confirm the presence of uranium and other minerals,'' said an ISRO official. 

Within two months of its launch, Chandrayaan-1 has found iron on the moon through a Nasa instrument, moon mineralogy mapper (M3). 

M3 principal investigator and NASA scientist Carle Pieters also confirmed the instrument's finding. Speaking on behalf of Nasa, Pieters said: "The mapper spectrometer has beamed images of the Orientale Basin region of the moon, indicating abundance of iron-bearing minerals such as pyroxene. Using different wavelengths of light, the instrument has also revealed, for the first time, changes in rock and mineral composition.'' 

Isro officials said M3 would help in characterising and mapping lunar minerals to ultimately understand the moon's early geological evolution. "The compositional map that will come out of M3 will have fantastic data on geological formation of the moon,'' the official said. 

Researchers said the relative abundance of magnesium and iron in lunar rocks could help confirm whether the moon was covered by a molten, magma ocean early on in its history. Iron and magnesium will also indicate melting of the moon, if it happened and how it formed later. This metallic element has been found in lunar meteorites, but scientists know little about its distribution in the lunar crust. 

After Luna 24 returned samples of lunar soil to Earth in August 1976, no otherspacecraft went to the moon until January 1994, when the US sent the orbiter Clementine. Then, the US probe Lunar Prospector orbited the moon from January 1998 to July 1999. The craft mapped the concentrations of chemical elements in the moon and surveyed the moon's magnetic fields. 

Interestingly, Chandrayaan's findings come after the last probe in 2003 -- SMART-1 spacecraft launched by the European Space Agency in 2003, went into orbit around the moon in 2004. The craft's instruments were designed to investigate the moon's origin and conduct a detailed survey of the chemical elements on the lunar surface. 

COLOUR IS THE KEY 

Moon Mineralogy Mapper (M3) is the first instrument to provide highly uniform imaging of the lunar surface. M3 provides scientists their first opportunity to examine lunar mineralogy at high spatial and spectral resolution. The Orientale Basin of moon, mapped by the Nasa instrument, is located on its western limb. Along with the length and width dimensions across a typical image, the instrument analyzes a third dimension — colour. The image showing blue to red tones reveal changes in rock and mineral composition, and the green colour is an indication of the abundance of iron-bearing minerals such as pyroxene. The image strip on the right is from a single wavelength of light that contains thermal emission, providing a new level of detail on the form and structure of the region's surface.


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