August 28, 2010
images from Maurice Collins
One of the most power techniques of professional planetary scientists is combining different data types into one visualization. Now, thanks to Jim Mosher's remarkable Lunar Terminator Visualization Tool, amateurs can use the same approach to explore data sets. Once again Maurice has led the way, creating a new multi-sensor depiction of the Humorum Basin area. The top image combines Earth-based 70 cm radar, Clementine color and LRO digital terrain model (DTM). To better understand the contribution of each data set I have placed small versions - in the sequence mentioned - under the composite image. The contribution of the DTM is easy to spot - it adds shadows and a sense of relief to the other two full Moon views. Disentangling radar and color requires closer comparisons, and is very worthwhile. The radar is definitely responsible for the bright ejecta halo surrounding Bullialdus (top right), but both the radar and color appear to contribute to the darkness of pyroclastics and/or lava in the southwest corner of Humorum and of the lavas just to the west. Surprisingly, the rays of Tycho that pass near Bullialdus on the Clementine image do not appear on the composite one. I am most fascinated by three areas near the dark-floored Billy (upper left). To the bottom-left of the crater and to the top-right there are gray smooth-looking patches. In the Clementine image these look like normal maria, but the radar clearly shows them as brighter, which generally means they have a rougher texture than the other lavas. Lunar Orbiter images show nothing unusual about these lavas. It is possible that their unusual physical character has not been previously noticed - and I am too tired to do a literature search to see if they are known. If they are, I assume it would be because of radar images.
Maurice explains: I combine them in Photoshop CS4 using the radar image as the base image (background), then add the DEM as a layer using blending mode "overlay", then I add the Clementine color image layer and use "color" as the blending mode for that layer. All at 100% opacity. The images need slight registering to the radar image, especially the Clem color as it doesn't overlay exactly, which is why I use LTVT for a best fit.
Rükl plate 52