Lattimer, AST 248, Lecture 21 p.1/18

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1 Lattimer, AST 248, Lecture 21 p.1/18

temperature and high gravity Major gases are N2 (98.4%), CH 4 (1.6%), Ar; smog (hydrocarbon, tholin) layer at high altitude.

2 Titan Only moon with dense atmosphere, 1.5 Earth s Saturn s largest satellite, 2nd in Solar System Spin tidally locked with Saturn In a 3:4 orbital resonance with Hyperion Atmosphere s existence a result of relatively cold formation temperature and high gravity Major gases are N2 (98.4%), CH 4 (1.6%), Ar; smog (hydrocarbon, tholin) layer at high altitude. Lack of noble gases Kr, Xe and Ne suggest atmosphere formed as a result of outgassing rather than by cometary impacts. Haze results in anti-greenhouse effect: opaque to visibile, clear to infrared. Methane (CH4 ) is present and must be replenished, indicating volcanos or lakes of methane or ethane (C 2 H 6 ). Cassini probe mapped surface in Surface temperature is 94 K, methane rain may exist Surface is complex, fluid-processed and geologically young (H 2 O and NH 3 volcanos?) Haze Lattimer, AST 248, Lecture 21 p.2/18

3 Titan s Interior Evidence for H 2 O-NH 3 sub-surface ocean from ELF (extremely long frequency radio waves 3400 km radius rocky core surrounded by several ice layers Ammonia (NH 3 ) lowers H 2 O freeezing point NASA Systematic shift of surfac implies crust floats on oc Lattimer, AST 248, Lecture 21 p.3/18

4 Titan s Climate Methane rains and ethane snows onto poles in winter and evaporate during summer. Titan s year is 30 Earth-years long. CH 4 NASA Lattimer, AST 248, Lecture 21 p.4/18

5 Hydrocarbon lakes Lattimer, AST 248, Lecture 21 p.5/18

6 Titan s Surface NASA Lattimer, AST 248, Lecture 21 p.6/18

7 Titan s Volcanoes and Lakes Cryovolcano Tortula Facula Cryovolcano Sotra Facula Lattimer, AST 248, Lecture 21 p.7/18

Life on Titan? Conditions on Titan might be suitable for some terrestrial psychrophiles, which utilize organic chemicals for both food and energy.

8 Life on Titan? Conditions on Titan might be suitable for some terrestrial psychrophiles, which utilize organic chemicals for both food and energy. Some key elements are liquid reservoirs, organic molecules and energy sources. Ultraviolet light reacting with nitrogen and methane in atmosphere produces hydrocarbons, visible as orange smog, which fall onto Titan s surface. Large organic molecules (tholins) up to 10,000 times the mass of Hydrogen have been found in Titan s high atmosphere, and are possibly responsible for the haze. Natural forces, such as shifting continental plates, wind erosion, lakes of ethane and methane, and volcanos, can alter the landscape. There may exist hot springs connnected to hydrocarbon reservoirs. Possible life could produce energy by mixing acetylene (C2 H 2 ), abundant in Titan s atmosphere, with hydrogen. Coldness is a real impediment, however, with surface temperature of 180 C which would make chemical reactions sluggish at best. Subsurface temperatures in liquid water layer could be much warmer ( 73 C). Early Titan was warmer, due to increased radioactivity and a warmer Saturn. In the future, as the Sun warms and becomes more luminous, temperatures will increase, reaching 70 C when the Sun becomes a red giant. Lattimer, AST 248, Lecture 21 p.8/18

of low melting-point liquid, not pure water, under surface.

9 Enceladus Small size, but geologically active Surface 90% reflective due to fresh ice Ice volcanos may be the source of Saturn s E-ring material Presence of low melting-point liquid, not pure water, under surface. Tidal resonance with Dione or Saturn may be source of heat Lattimer, AST 248, Lecture 21 p.9/18

10 Lattimer, AST 248, Lecture 21 p.10/18

11 Lattimer, AST 248, Lecture 21 p.11/18

12 Saturn s E ring with Enceladus Tethys Enceladus south polar jets Lattimer, AST 248, Lecture 21 p.12/18

13 Lattimer, AST 248, Lecture 21 p.13/18

14 Iapetus Iapetus has leading hemisphere which is dark (carbon-rich) and a trailing hemisphere which is bright (ice). Dark material may be deposited from matter chipped off Phoebe, a very dark satellite; this matter may also coat Hyperion. Orbit is highly inclined. Equatorial bulge Lattimer, AST 248, Lecture 21 p.14/18

15 Phoebe and Hyperion Small Saturn satellites Phoebe has retrograde orbit and very rocky, indicating it is a captured Kuiper Belt object. Phoebe is very dark: albedo is 0.06 Hyperion is 2nd largest irregular body in solar system; Neptune s Proteus is larger. Phoebe Hyperion Lattimer, AST 248, Lecture 21 p.15/18

Mimas Mimas clears the material from the Cassini Division, the gap between Saturn s two widest rings, because that location is in a 2:1 orbital resonance with Mimas Impact that

16 Mimas Mimas clears the material from the Cassini Division, the gap between Saturn s two widest rings, because that location is in a 2:1 orbital resonance with Mimas Impact that produced the large crater (Herschel) almost completely shattered Mimas; an equivalently-sized crater on the Earth would be as wide as the U.S. Lattimer, AST 248, Lecture 21 p.16/18

Triton Largest satellite of Neptune, third-most massive moon in solar system Only large moon with a retrograde orbit, probably originally a binary Kuiper Belt object that was captured and disrupted

17 Triton Largest satellite of Neptune, third-most massive moon in solar system Only large moon with a retrograde orbit, probably originally a binary Kuiper Belt object that was captured and disrupted Decaying orbit will take Triton within Neptune s Roche Limit, causing breakup in 3.6 Gyr. Thin atmosphere of N 2 and CH 4 Few craters, active N2, H 2 O, CH 4 cryovolcanos and geysers; relatively young surface < 50 million years old No tidal heating, but seasonal solar heating creates a solid-state (ice) Greenhouse effect; geysers observed are located only near subsolar point. Lattimer, AST 248, Lecture 21 p.17/18

18 Dark streaks of dust left by nitrogen geysers Lattimer, AST 248, Lecture 21 p.18/18

2007 Pearson Education Inc., publishing as Pearson Addison-Wesley. The Jovian Planets

2007 Pearson Education Inc., publishing as Pearson Addison-Wesley. The Jovian Planets The Jovian Planets The Jovian planets are gas giants - much larger than Earth Sizes of Jovian Planets Planets get larger as they get more massive up to a point... Planets more massive than Jupiter are