We investigate the effects of varying Saturn ’ s orbit on the atmospheric circulation and surface methane distribution of Titan .
Using a new general circulation model of Titan ’ s atmosphere , we simulate its climate under four characteristic configurations of orbital parameters that correspond to snapshots over the past 42 kyr , capturing the amplitude range of long-period cyclic variations in eccentricity and longitude of perihelion .
The model , which covers pressures from the surface to 0.5 mbar , reproduces the present-day temperature profile and tropospheric superrotation .
In all four simulations , the atmosphere efficiently transports methane poleward , drying out the low- and mid-latitudes , indicating that these regions have been desert-like for at least tens of thousands of years .
Though circulation patterns are not significantly different , the amount of surface methane that builds up over either pole strongly depends on the insolation distribution ; in the present-day , methane builds up preferentially in the north , in agreement with observations , where summer is milder but longer .
The same is true , to a lesser extent , for the configuration 14 kyr ago , while the south pole gains more methane in the case for 28 kyr ago , and the system is almost symmetric 42 kyr ago .
This confirms the hypothesis that orbital forcing influences the distribution of surface liquids , and that the current observed asymmetry could have been partially or fully reversed in the past .
The evolution of the orbital forcing implies that the surface reservoir is transported on timescales of \sim 30 kyr , in which case the asymmetry reverses with a period of \sim 125 kyr .
Otherwise , the orbital forcing does not produce a net asymmetry over longer timescales , and is not a likely mechanism for generating the observed dichotomy .