AGU/Idaho: Evidence of Changing Seasons, Rain on Titan's North Pole

[bystander]

Evidence of Changing Seasons, Rain on Titan's North Pole
American Geophysical Union | University of Idaho | 2019 Jan 16

Titan’s north pole as seen by the Cassini Visual and Infrared Mapping Spectrometer. The orange box shows the “wet sidewalk” region, what analyses suggests is evidence of changing seasons and rain on Titan’s north pole. The blue box shows the expanded region in the bottom panel. Bottom Panel: Pictured is an expanded view of Titan’s north pole. Dark blue arrows mark clouds. Red arrows mark the mirror-like reflection from a lake called Xolotlan Lacus. Pink arrows mark the “wet sidewalk”region. The black dot marks the actual north pole of Titan. Light blue arrows mark the edges of the largest north polar sea, Kraken Mare. Credit: NASA/JPL-Caltech/University of Arizona/University of Idaho

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An image from the international Cassini spacecraft provides evidence of rainfall on the north pole of Titan, the largest of Saturn’s moons. The rainfall would be the first indication of the start of a summer season in the moon’s northern hemisphere. ...

Dhingra and her colleagues identified a reflective feature near Titan’s north pole on an image taken June 7, 2016, by Cassini’s near-infrared instrument, the Visual and Infrared Mapping Spectrometer. The reflective feature covered approximately 46,332 square miles, roughly half the size of the Great Lakes, and did not appear on images from previous and subsequent Cassini passes.

Analyses of the short-term reflective feature suggested it likely resulted from sunlight reflecting off a wet surface. The study attributes the reflection to a methane rainfall event, followed by a probable period of evaporation. ...

This reflective surface represents the first observations of summer rainfall on the moon’s northern hemisphere. If compared to Earth’s yearly cycle of four seasons, a season on Titan lasts seven Earth years. Cassini arrived at Titan during the southern summer and observed clouds and rainfall in the southern hemisphere. Climate models of Titan predicted similar weather would occur in the northern hemisphere in the years leading up to the northern summer solstice in 2017. But, by 2016, the expected cloud cover in the northern hemisphere had not appeared. This observation may help scientists gain a more complete understanding of Titan’s seasons. ...

Observational Evidence for Summer Rainfall at Titan's North Pole ~ Rajani Dhingra et al

• Geophysical Research Letters (online 16 Jan 2019) DOI: 10.1029/2018GL080943