May 11, 2015

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Galileo's Colorful Moon

Originally published May 10, 2004


Image Credit: JPL Photojournal

Galileo's Colorful Moon

The Moon is a mono-color sphere - shades of grey, chromatically bounded by some whitish glare and black shadows. The problem is that our eyes, so wonderfully sensitive to faint light and subtle hues aren't good enough. But spacecraft can use filters to image in wavelengths that are sensitive to particular elements, and then computers can exaggerate the colors so that our humble Moon looks like a gaudy Christmas ornament. Such colorized views are good because they help us understand the differences in composition and sometimes age of different parts of the Moon. And we can carry that knowledge back to the eyepiece when observing. The colors show, as we know from black and white views, that there are two major types of lunar materials. The cratered highlands are made largely of iron-poor rocks which show up red in this 3-filtered image. You can see though that not all highlands are the same - an orangish area near Schickard (bottom left), and near the north pole must have some compositional differences. And the maria also have differ shades of blue and even some golden hues, showing that they are not all identical. The brightest blue in Tranquillitatis is due to titanium-rich lavas, and the orange mare (parts of Imbrium, Frigoris and Serenitatis) are lower titanium lavas. Patches of purple blue (SE of Copernicus) are due to pyroclastic (ashy, sort of) rocks. The brightest areas are the freshly (well, in the last billion years or so) crushed and exposed surfaces of young impact craters. Tycho and its rays are clear, but so are Aristarchus, Copernicus, Proclus, and various smaller craters west of Nectaris, near the north pole, and even just west of Plato. Take a look.

Technical Details:
Imaged December 8, 1992 by Galileo Solid State Imaging CCD Camera.

Related Links:
National Space Science Data Center
Amateur Version

Yesterday's LPOD: The Crater Formerly Known As Prinz

Tomorrow's LPOD: Who Named That Crater?

Author & Editor:
Charles A. Wood



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