Don Campbell of Cornell University delivered this week’s DTM seminar entitled, “The radar reflection properties of icy surfaces in the Solar System and the search for lunar ice.” Campbell presented an overview of radar astronomy and its application to the study of asteroids, the terrestrial planets and the icy satellites of the outer Solar System. Campbell highlighted his particular interest in testing for the presence of ice at the lunar poles, the subject of a 19 October 2006 article his and his colleagues published in Nature.

Photo courtesy Cornell University.

In the article, entitled, “No evidence for thick deposits of ice at the lunar south pole,” Campbell and colleagues argue that there is no evidence for concentrated deposits of water ice in Shackleton crater on the Moon or elsewhere near its south pole. The possible presence of water-ice deposits in polar areas of the Moon has been a controversial issue since the mid-1990s. Shackleton crater has been suggested in the past as a possible site of concentrated deposits of water ice, on the basis of modeling bi-static radar polarization properties and interpretations of earlier Earth-based radar images. Such an interference, if correct, would have a significant impact on planning for future lunar landings.

According to Campbell and colleagues, these earlier Earth-based radar data lack the resolution and coverage for detailed studies of the relationship between radar scattering properties, cold traps in permanently shadowed areas, and local terrain features. Campbell and colleagues present new 20-m-resolution, 13-cm-wavelength radar images indicating that the polarization properties normally associated with reflections from icy surfaces in the Solar System were found at all the observed latitudes and are strongly correlated with the rock-strewn walls and ejecta of young craters, including the inner wall of Shackleton. Campbell and colleagues write, "If the hydrogen enhancement observed by the Lunar Prospector orbiter indicates the presence of water ice, then our data are consistent with the ice being present only as disseminated grains in the lunar regolith."