Small Scale Roughness of the Moon: Inversion of Diviner Measurements

Small Scale Roughness of the Moon: Inversion of Diviner Measurements

Paul Hayne1, Oded Aharonson2,1, Joshua Bandfield3, Meg Rosenburg1, David Paige4, and the Diviner Team

1California Institute of Technology2Weizmann Institute of Science

3University of Washington4University of California, Los Angeles

Temperatures in Shadow and Sunlight

Sunlit surfaces nearly in radiative equilibrium (400 K at normal solar incidence)

Shadows much colder; conduction from subsurface balances thermal emission (100 K at midnight)

Infrared Emission from a Rough Surface

Emission at shorter wavelengths dominated by warmer facets (two Diviner channels indicated by arrows)

Surface Roughness Example: Apollo 11

• Best-fit RMS slope 20 – 30

• Model fit quality changes with local time… poor modeling of shadow temperatures?

Comparison to Apollo Landing Sites

Scale (millimeters)RM

S slo

pe

Helfenstein and Shepard (1999)

Problem: We should not be able to see roughness below the thermal skin depth of a few centimeters, yet RMS slopes match sub-millimeter values from Apollo…

Roughness at What Scale?

Preliminary Roughness Map

RMS surface slopes, derived from channels 4 and 7, corrected for emissivity(We are working on a global map, but emissivity correction is challenging at higher latitudes.)

Preliminary Roughness MapLOLA 17-m baseline slopes (Rosenburg et al. 2011)

LPSC (2012)