Scientists propose moon-based climate observatory

Global climate change is driven by an imbalance between incoming energy from the sun and outgoing energy from Earth. Without understanding the climate system's inputs and outputs---its so-called energy budget---it is impossible to tease out the relative contributions of natural and human-induced influences and to predict future climate, Huang said.

But detecting changes in the energy budget is difficult with existing ground-based and space-borne technologies, he noted. Fortunately, instruments left behind by the Apollo 15 astronauts---all U-M alumni, incidentally---inadvertently provided just the necessary measurements.

"One of the main scientific objectives of the Apollo 15 mission was to drill two boreholes about three meters into the lunar soil and insert specially designed probes," Huang said. "The point was to see how temperature varies with depth, in order to calculate the heat flow outward from the interior of the moon." But drilling in the moon's powdery soil, or regolith, turned out to be much more difficult than expected..

On the near side of the airless moon, where Apollo 15 landed, surface temperature is controlled by solar radiation during daytime and energy radiated from Earth at night. Huang showed that due to an amplifying effect, even weak radiation from Earth produces measurable temperature changes in the regolith. Further, his revisit of the data revealed distinctly different characteristics in daytime and nighttime lunar surface temperature variations.