Cassini/VIMS Observations of Titan’s North-South Asymmetry From 2004-2017

We document the evolution of the North-South Asymmetry (NSA) of Titan’s haze albedo during the Cassini mission between 2004 and 2017. We use co-added visible and near-infrared images taken by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) instrument from fourteen Titan flybys to enhance the contrast of the NSA. Over a half-Titan year, we observe a near-complete transition in the NSA boundary latitude across the geographic equator from the Southern to Northern hemisphere, including a 3-year loss in albedo contrast several years after the vernal equinox. The NSA disappearance matches observations of a reversal of the NSA in Hubble images before winter solstice between 1997-2000 (Lorenz et al., 2001) and in Space Telescope Imaging Spectrograph images between 2017-2019 (Karkoschka, 2022). A comparison of NSA images taken at similar times but at different phase angles shows the NSA boundary is detectable, albeit with less contrast, at high phase angles (~90 degs). We find several VIMS cube images further support a small yet detectable tilt between the super-rotating atmosphere and the solid body of Titan, as previously suggested in an analysis of 890 nm images from the Cassini Imaging Science Subsystem (ISS) by Roman et al. (2009).

References:

1. Karkoschka, E. 2022, Icarus, 115188

2.Lorenz, R., Young, E., & Lemmon, M. 2001, Geophysical research letters, 28, 4453

3. Roman, M. T., West, R. A., Banfield, D., et al. 2009, Icarus, 203, 242