Lm. Dougherty et Je. Geake, POLARIZATION BY FROST FORMED AT VERY-LOW TEMPERATURES, AS RELEVANT TOICY PLANETARY SURFACES, Monthly Notices of the Royal Astronomical Society, 271(2), 1994, pp. 343-354
Optical polarization by water-ice frost formed at temperatures down to
100 K is measured, and found to be significantly different from that
previously observed for terrestrial ice and frost; the difference is g
reatest for frost with very small - possibly subwavelength - ice cryst
als, formed by very rapid cooling of a small amount of water vapour: t
his is found to give deep negative polarization at a small phase angle
, and a high value of slope. Assembled ice and frost data give a new s
lope/albedo relationship, significantly different both from the well-e
stablished relationship for terrestrial and planetary rocks, and from
the intermediate band for opaque light-coloured powders. This new rela
tionship is relevant to the interpretation of observations of icy plan
etary satellites. The UMIST polarimeter, with its low-temperature samp
le holder, is described.