May 4, 2014
Pkt Worms
Plots from Andrews-Hanna and colleagues, LPSC
These three color data images are centered on the PKT, the Procellarum KREEP Terrane, the most radioactive-rich region of the Moon and the region where most lunar maria occur. Jeffrey Andrews-Hanna and colleagues include these maps in their abstract from the recent Lunar and Planetary Science Conference. Map a shows gravity gradients (with blue areas where the gravity value most rapidly changes. Imbrium is the near-center light blue circle, and Serenitatis, Crisium and Nectaris are deeper blue circles to the right. This map includes a number of lunar worms that outline the PKT. They can be better seen in plots b and c as black lines segments. Chart b shows topography with blues being low, and chart c displays thorium, which is the main geochemical marker for the PKT. Andrews-Hanna and colleagues propose that these dark lines are lava-filled crustal fractures that fed magma from the mantle to form many of the nearside maria. The rectangular distribution of these lines/fractures is nearly the same as the surface structures Ewen Whitaker long ago used to defined the the giant Procellarum impact basin, but the Andrews-Hanna team proposes that that basin doesn't exist. I wish I had been at their LPSC presentation for I am not convinced that the dark lines are not a deep manifestation of the Procellarum Basin, rather than fractures due to thermal expansion and contraction of lunar crust and mantle. The dark lines - the worms - are real, their interpretation may yet evolve.
Chuck Wood
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