June 4, 2021

Redder Spots

Originally published October 16, 2011
image from NASA/GSFC/Arizona State University. LRO WAC Color R 566nm, G 360nm, B 321 nm. Red SPots: R Riphaeus Mts, H Helmet, D Darney, L Lassell.

In the late 1950s, when few scientists studied the Moon, Ewen Whitaker borrowed a technique from Fritz Zwicky, a galactic astronomer, to image the Moon through red and blue filters. By combining these images in a way to eliminate albedo, Ewen was able to identify regions of distinctly different colors, which we now know reflect different soil compositions. Jim Head and I studied Ewen's images and described a number of red spots that seemed like they might be volcanic rocks with compositions different than mare lavas. Now, color filtered images with the Wide Angle Camera of the Lunar Reconnaissance Orbiter have updated Ewen's color contrast images with much higher resolution. Maria with medium to high titanium contents are blue, but what is interesting here are the very red, low titanium red spots labeled with letters. Each represents a non-mare volcanic area, that we know, but what controls their distribution is still uncertain.

Chuck Wood

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