http://arxiv.org/abs/1508.05924
We present the results of an investigation to determine the longitudinal distributions and temporal evolution of ices on the surface of Triton. Between 2002 and 2014, we obtained 63 nights of near-infrared (0.7-2.5 $\mu$m) spectra using the SpeX instrument at NASA’s Infrared Telescope Facility (IRTF). Triton has spectral features in this wavelength region from N$_2$, CO, CH$_4$, CO$_2$, and H$_2$O. An absorption feature at 2.405 $\mu$m could be due to either ethane (C$_2$H$_6$) or $^{13}$CO. We calculated the equivalent width (or fractional band depth in the case of H$_2$O) in each nightly average spectrum, constructed longitudinal distributions, and quantified temporal evolution for each of the chosen absorption bands. The volatile ices (N$_2$, CO, CH$_4$) show significant variability over one Triton rotation and have well-constrained longitudes of peak absorption. The non-volatile ices (CO$_2$, H$_2$O) show poorly-constrained peak longitudes and little variability. The longitudinal variability of the 2.405 $\mu$m band resembles the non-volatile ices and is consistent with ethane absorption. N$_2$ and CH$_4$ absorption increased over the period of the observations, whereas absorption from the non-volatiles remained constant. We conclude from these results that the southern latitudes of Triton are currently dominated by non-volatile ices and as the sub-solar latitude migrates northwards, a larger quantity of volatile ices are coming into view.
B. Holler, L. Young, W. Grundy, et. al.
Tue, 25 Aug 15
23/69
Comments: 29 pages, 15 figures, 4 tables, appendix