The electric blue crater on our moon.

Photo 1: Aristarchus crater

The region of the Aristarchus plateau has been the site of many interesting observation reports, raising questions about the source of the blue and reddish light from this crater. Such reports document a number of processes seen through telescopes and from manned spacecrafts, including  temporary obscurations and colourations of the surface.

In 1971 when Apollo 15 passed 110 kilometers above the Aristarchus plateau, a significant rise in alpha particles was detected. These particles are believed to be caused by the decay of radon-222, a radioactive gas with a half-life of only 3.8 days. The Lunar Prospector mission later confirmed radon-222 emissions from this crater.

An interesting report published in by the United States Air Force in May 1964 documents the peculiarity of this crater, which was a subject of much debate at the time. The inset below in Photo 2 shows the observation of a reddish hue in the region highlighted in 1963, which is similar to the area I observed in photo 1 above. This report is available here. This is apart from the strong blue colour in the remaining parts of the crater. This observation discredits those who say that the lunar surface is devoid of both colour and phenomena.

Photo 2: Source - United States Air Force, 1964.

My image is composed of individual colour channel images and overlayed to create an RGB composite. Blue and Magenta colours were slightly enhanced to bring out these two colourations in the crater. The final image was cropped to reflect changes in the immediate vicinity and interior of Aristarchus crater.
During the 4 minute period, a weak red colour on the southern part of the inner walls of Aristarchus was evident, similar to that reported in 1963 by Greenacre and Barr. The remaining parts of the inner walls and crater floor looked normal.

However, a trace orange-red delineation is evident on the northwestern part of the inner walls.


Equipment & Software Used:
Nexstar 8SE at f10
CGE
DMK 31AF  monochrome
IC Software
Astronomik filters  R – G – B - CLS
Astrodon IR Pass 742

Atmospheric conditions @ 1800UT:
Ambient air temperature: 24degC
Dew point: 22degC
Wind: 04 knots SSW
Haze visible, 8km visibility
Clear sky