Evolution of Titan and implications for its hydrocarbon cycle

Research areas:
Year:
2009
Authors:
Journal:
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
Volume:
367
Number:
1889
Pages:
617-631
Month:
FEB 28
ISSN:
1364-503X
Abstract:
Measurements of the carbon and nitrogen isotopic ratios as well as the
detection of Ar-40 and Ar-36 by the gas chromatograph mass spectrometer
(GCMS) instrument on board the Huygens probe have provided key
constraints on the origin and evolution of Titan's atmosphere, and
indirectly on the evolution of its interior. Those data combined with
models of Titan's interior can be used to determine the story of
volatile outgassing since Titan's formation. In the absence of an
internal source, methane, which is irreversibly photodissociated in
Titan's stratosphere, should be removed entirely from the atmosphere in
a time-span of a few tens of millions of years. The episodic
destabilization of methane clathrate reservoir stored within Titan's
crust and subsequent methane outgassing could explain the present
atmospheric abundance of methane, as well as the presence of argon in
the atmosphere. The idea that methane is released from the interior
through eruptive processes is also supported by the observations of
several cryovolcanic-like features on Titan's surface by the mapping
spectrometer (VIMS) and the radar on board Cassini. Thermal
instabilities within the icy crust, possibly favoured by the presence of
ammonia, may explain the observed features and provide the conditions
for eruption of methane and other volatiles. Episodic resurfacing events
associated with thermal and compositional instabilities in the icy crust
can have major consequences on the hydrocarbon budget on Titan's surface
and atmosphere.