Turtle, E.P., Perry, J.E., McEwen, A.S., Barbara, J., Delgenio, A., West, R.A. (2009). "Cassini ISS observations of seasonal changes in Titan's meteorology and surface features" Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract P54C-01.


Abstract
Since Cassini's arrival at Saturn the season has progressed from northern winter to just past the northern vernal equinox (the equivalent of ~mid-January to late March on Earth), driving changes in the weather patterns. Until shortly after Cassini arrived at Saturn, large convective cloud systems were common over the South Pole. Since 2005, such storms have been less common and elongated streaks of clouds have been observed further and further to the north, becoming common at high northern latitudes by 2007. Cassini's Imaging Science Subsystem (ISS) has also observed changes in surface features at high southern latitudes: a new large dark area appeared between July 2004 and June 2005 and may have subsequently faded; recent observations of Ontario Lacus suggest that its boundary may have receded somewhat as well. Such changes are interpreted to be the result of precipitation and ponding of liquid methane and the subsequent evaporation thereof. Intriguingly, Cassini RADAR observations of areas near Titan's south pole reveal far fewer lakes than are observed by RADAR at high northern latitudes and fewer than suggested by the number of dark features observed by ISS in this area. This apparent discrepancy may simply be a result of the fact that not all dark features identified by ISS are liquid-filled; however another possible explanation is that evaporation has occurred between the ISS observations in mid-2005 and RADAR observations of similar territory starting in 2007. Further investigation of comparison of ISS and RADAR observations is underway to better understand the implications of the differences observed. We will present observations of Titan's atmospheric behavior and surface features, documenting changes that have resulted from weather and seasonal change.