Friday, September 25, 2009

How to find water on the Moon

Graphs showing detailed measurements of light as a function of color or wavelength. The data, called spectra, are used to identify minerals and molecules. On the left spectra of lunar rocks, minerals and regolith returned to Earth by Apollo in visible to shorter-wavelengths IR range. The blue bar shows where a dip in the light is expected due to the presence of water and hydroxyl molecules. To the right are model spectra for pure water (H2O) and hydroxyl (OH-). [ISRO/NASA/JPL-Caltech/Brown]

These images from NASA's Moon Mineralogy Mapper (3M or '3-Qubed') on board the Indian Space Research Organisation (ISRO) Chandrayaan lunar orbiter show data for the near side. The image above shows albedo, or sunlight reflected sunlight from the lunar surface. The image below shows where infrared light is absorbed in a manner characteristic of the presence of water and hydroxyl molecules, most strongly at the cool, higher latitudes near the poles. The blue arrow indicates Goldschmidt crater, a large and feldspar-rich region with a bright water and hydroxyl signature. [ISRO/NASA/JPL-Caltech/Brown Univ.]

Goldschmidt crater, in the far northern hemisphere of the Moon as that region would be seen from Earth on the evening of this posting (Virtual Moon Atlas v.4) if it were possible to peer into the Moon's shadow, ahead of First Quarter when the sunrise terminator relief makes that region most conspicuous. The 127 km wide crater at 73° north is older than most similar features visible on the moon and dates from the pre-Nectarian, between the Moon's birth ~4.575 billion years and 3.9 billion years old.

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