To Sea or Not to Sea: Titan's Paradigm Malfunction
R. M. Nelson, R. H. Brown, W. D. Smythe, B. W. Hapke, L. Kamp, M. Boryta, K. H. Baines, G. Bellucci, J.-P. Bibring, B. J. Buratti, F. Capaccioni, P. Cerroni, R. N. Clark, A. Coradini , D. P. Cruikshank, P. Drossart, V. Formisano, R. Jaumann, Y. Langevin, D. L. Matson, T. B. McCord, V. Mennella, P. D. Nicholson, B. Sicardy and C. Sotin- Funded by the Cassini-Huygens Mission to Saturn and Titan
A single paradigm that had been developed to study the Saturnian system and its largest moon, Titan, has been shaken to its core, as scientists discover that there is no evidence that the large circular regions on Titan have accumulations of liquid of any form.
Analyzing data from the Cassini Visual & Infrared Mapping Spectrometer (VIMS), Nelson, et. al. studied images and photometric properties of several large circular regions on Titan's surface at infrared wavelengths and concluded that they may not be craters despite their strong likeness to similar regions seen on the Moon, Mercury, Venus and Mars.
The investigations of the light reflected from the interiors of those regions show that the features may be palimpsests or penepalimpsests rather than real craters. Palimpsests are the remains of ancient craters that have filled in by the slow flow of crustal material over eons of time from the crater walls. Palimpsests are found on the icy Galilean satellites Ganymede and Callisto.
Significance to Solar System Exploration
In recent years, scientists spoke with confidence that much of Titan's surface was covered by oceans of hydrocarbon liquids. The publication New Scientist was quoted a year ago as saying that "the liquid will accumulate in perhaps as many as 80 craters of 150 km size or greater...." However, the features found on Titan are very large, typically 1000 km across. Therefore, if they were the remains of impacts then these would be survivors of an early period in time about 3-4 billion years ago, a period that solar system geologists call the "late heavy bombardment." If they are that old and have remained relatively undisturbed on Titan's surface for more than a billion years then they have not been covered over by solid precipitation or 'snow' from Titan's atmosphere. They also would have been remarkably resistant to erosion by liquid precipitation for long periods of time. This suggests that the widespread precipitation on Titan's surface that had been expected may be limited.
Implications
Since the data analysis found no evidence to date that supports the existing paradigm that Titan has vast accumulations of liquids on its surface, the paradigm will subsequently need to be changed to accommodate these new findings. This will undoubtedly create a harbinger of uncertainty and confusion as scientists scramble to understand the nature of Titan and begin a new paradigm to observe and understand this fascinating moon.
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