TEMPERATURE OF NITROGEN ICE ON PLUTO AND ITS IMPLICATIONS FOR FLUX MEASUREMENTS

Previous work by K. A. Tryka et al. (Science 261, 751-754, 1993) has shown that the profile of the 2.148-mu m band of solid nitrogen can be used as a ''thermometer'' and determined the temperature of nitrogen ice on Triton to be 38(-1)(+2) K. Here we reevaluate that data and refine the temperature value to 38 +/- 1 K. Applying the same technique to Pluto we determine that the temperature of the N-2 ice on that body is 40 +/- 2 K. Using this result we have created a nonisothermal flux model of the Pluto-Charon system, The model treats Pluto as a body with symmetric N-2 polar caps and an equatorial region devoid of N-2. Comparison with the infrared and millimeter flux measurements shows that the published fluxes are consistent with models incorporating extensive N-2 polar caps (down to +/-15 degrees or 20 degrees latitude) and an equatorial region with a bolometric albedo less than or equal to 0.2. (C) 1994 Academic Press, Inc.