Walter Kiefer

This is important because it controls the rate of internal geologic activity on the Moon, for context, the thermal energy coming out of Earth controls the rate at which Earth's geologic plates move, the development of mountain ranges, earthquake activity and volcanic eruptions.

The mystery persisted for so long because no one was working on this problem, nASA began an effort at recovering old mission data [ Apollo and other spacecraft ] in 2010, when our team began working on this problem.

This was very localized in the regions where the astronauts worked extensively, in these areas, the astronaut bootprints darkened the lunar regolith [ or soil ] slightly, causing the regolith to absorb more sunlight and heat up. This was a region 50 to 100 meters across in the experiment deployment zone and of similar or smaller sizes at the sample collection stops. Outside of these zones, the astronauts had little or no effect on the subsurface temperatures.

By adding the new data into the study, we now understand the data trends and can reliably interpret the experiment results.