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Laboratory measurements of cryogenic liquid alkane microwave absorptivity and implications for the composition of Ligeia Mare, Titan
Author(s) -
Mitchell Karl L.,
Barmatz Martin B.,
Jamieson Corey S.,
Lorenz Ralph D.,
Lunine Jonathan I.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl059475
Subject(s) - methane , titan (rocket family) , hydrocarbon , alkane , geology , polar , astrobiology , atmospheric sciences , chemistry , physics , organic chemistry , astronomy
The complex dielectric constants of liquids methane and ethane were measured at 90 K and 14.1 GHz, close to the frequency of the Cassini RADAR. The liquid ethane loss tangent is far greater than that of liquid methane, facilitating discrimination by remote sensing. The results suggest a methane‐dominated composition for the northern sea, Ligeia Mare, on the basis of a recent loss tangent determination using Cassini RADAR altimetry. This contrasts a previous far higher loss tangent for the southern lake, Ontario Lacus, which is inconsistent with simple mixtures of methane and ethane. The apparent nonequilibrium methane‐to‐ethane ratio of Ligeia Mare can be explained by poor admixture of periodically cycled methane with a deeper ethane‐rich alkanofer system, consistent with obliquity‐driven volatile cycling, sequestration of ethane from the hydrocarbon cycle by incorporation into crustal clathrate hydrates, or periodic flushing of Ligeia Mare into adjacent Kraken Mare by fresh rainfall.