Low-Latitude Ethane Rain on Titan

Dalba, Paul A.; Buratti, Bonnie J.; Brown, R. H.; Barnes, J. W.; Baines, K. H.; Sotin, C.; Clark, R. N.; Lawrence, K. J.; Nicholson, P. D.

NASA NTRS · 20150005664

Low-Latitude Ethane Rain on Titan

Dalba, Paul A.·Buratti, Bonnie J.·Brown, R. H.·Barnes, J. W.·Baines, K. H.·Sotin, C.·Clark, R. N.·Lawrence, K. J.·Nicholson, P. D.

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Abstract

Cassini ISS observed multiple widespread changes in surface brightness in Titan's equatorial regions over the past three years. These brightness variations are attributed to rainfall from cloud systems that appear to form seasonally. Determining the composition of this rainfall is an important step in understanding the "methanological" cycle on Titan. I use data from Cassini VIMS to complete a spectroscopic investigation of multiple rain-wetted areas. I compute "before-and-after" spectral ratios of any areas that show either deposition or evaporation of rain. By comparing these spectral ratios to a model of liquid ethane, I find that the rain is most likely composed of liquid ethane. The spectrum of liquid ethane contains multiple absorption features that fall within the 2-micron and 5-micron spectral windows in Titan's atmosphere. I show that these features are visible in the spectra taken of Titan's surface and that they are characteristically different than those in the spectrum of liquid methane. Furthermore, just as ISS saw the surface brightness reverting to its original state after a period of time, I show that VIMS observations of later flybys show the surface composition in different stages of returning to its initial form.

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Dalba, Paul A., Buratti, Bonnie J., Brown, R. H., Barnes, J. W., Baines, K. H., Sotin, C., Clark, R. N., Lawrence, K. J., Nicholson, P. D.. 2012-08-01. Low-Latitude Ethane Rain on Titan. https://ntrs.nasa.gov/citations/20150005664

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