1. Titan’s lost seas found — The lakes of Titan Nature Vol. 445,4 January 2007 Chen Chih-Wei 1/9 2007

2. Titan: 1. dense atmosphere 2. 1.5 times surface pressure larger than earth 3. nitrogen is the principal component of its atmosphere ( like earth)

3. Lakes : 1. found only at high latitude (northern hemisphere) 2. The lakes are not formed of water, as they would be in earthly climes, but of the second most abundant component of Titan’s atmosphere, methane ( CH 4 ). 3. season progress : expand in winter shrink in summer

4. Observation : 1. Cassini Radar flyby of Titan on 22 July 2006(T 16 ) 2. radar–dark patches are interpreted as lakes on the basis of their very low radar reflectivity and morphological similarities to lakes.

8. methane ( CH 4 ): 1. thermodynamically allowed phase on the surface of Titan 2. lifetime of methane is short ( tens of millions of years) 3. replenishment: (a) methane-rich hydrocarbon ocean (x) (b) underground methane reservoirs (cryovolcanic process)

9. Hydrological cycle activity

10. Titan’s northern hemisphere lakes probably participate in a methanological cycle that has multiple timescales: (a.) 29-years cycle (season progress) (b.) 10 3 years (methane thunderstorm in mid- latitude and equatorial regions) (c.) millions of years (photochemistry) (d.) unknown ( cryovolcanic events, impact- generated release of methane stored below the surface )

11. ~~Thank you~~