Principal Component Analysis of Titan’s surface composition at Middle Latitudes

We present an investigation of Titan’s surface spectra order to determine the composition of Titan’s surface on a global scale and to identify and map the surfaces where water ice “bedrock” is exposed, despite the ongoing sedimentation of organic material from the atmosphere. This work follows the method established by an analysis of Titan’s tropical surface from 30S to 30 N latitudes (Griffith et al. 2017, submitted for publication). Similarly, we conduct a Principal Components Analysis (PCA) of the 4 wavelengths that most clearly view Titan’s surface (1.1, 1.3, 1.6, and 2.0 μm). However, here we investigate target Titan’s middle latitudes extending to 60S to 60 N. In contrast to previous analyses, which yield consistent results, this study identifies and deconstructs the major spectral components of the surface on a global scale, without prior assumptions regarding the surface composition and atmospheric scattering and absorption, as assumed from radiative transfer analyses. In addition, this approach by virtue of sampling the correlations among the 4096 spectra that make up a VIMS cube can identify subtle spectral features that would not be apparent in a single spectrum.The PCA analysis is conducted on over 100,000 VIMS spectra to determine the spectral trends that define the greatest spectral variance (the principal component) as well as successively lesser orthogonal correlations between the I/F values at each wavelength. The orthogonal spectral trends are derived by calculating the eigenvalues and eigenvectors of the covariance matrix, defined by the I/F values at the 4 window wavelengths of each cube and their deviations from their mean values.This presentation will discuss the PCA analysis and compare our derived compositional maps of Titan’s surface with Radar maps of the topography and morphology, to entertain questions regarding the geology of Titan’s surface the age of its atmosphere.