Spatial and temporal variations in Titan's surface temperatures from Cassini CIRS observations

V. Cottini, C. A. Nixon, D. E. Jennings, R. de Kok, N. A. Teanby, P. G. J. Irwin, F. M. Flasar

Research output: Contribution to journalArticle (Academic Journal)peer-review

46 Citations (Scopus)

Abstract

We report a wide-ranging study of Titan's surface temperatures by analysis of the Moon's outgoing radiance through a spectral window in the thermal infrared at 19 mu m (530 cm(-1)) characterized by lower atmospheric opacity. We begin by modeling Cassini Composite Infrared Spectrometer (CIRS) far infrared spectra collected in the period 2004-2010, using a radiative transfer forward model combined with a non-linear optimal estimation inversion method. At low-latitudes, we agree with the HASI near-surface temperature of about 94K at 10 degrees S (Fulchignoni et al., 2005). We find a systematic decrease from the equator toward the poles, hemispherically asymmetric, of similar to 1 K at 60 degrees south and similar to 3 K at 60 degrees north, in general agreement with a previous analysis of CIRS data (Jennings et al., 2009), and with Voyager results from the previous northern winter. Subdividing the available database, corresponding to about one Titan season, into 3 consecutive periods, small seasonal changes of up to 2 K at 60 degrees N became noticeable in the results. In addition, clear evidence of diurnal variations of the surface temperatures near the equator are observed for the first time: we find a trend of slowly increasing temperature from the morning to the early afternoon and a faster decrease during the night. The diurnal change is similar to 1.5 K, in agreement with model predictions for a surface with a thermal inertia between 300 and 600J m(-2) s(-1/2) K-1. These results provide important constraints on coupled surface-atmosphere models of Titan's meteorology and atmospheric dynamic. (C) 2011 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)62-71
Number of pages10
JournalPlanetary and Space Science
Volume60
Issue number1
DOIs
Publication statusPublished - Jan 2012

Cite this