Titan’s Lakes and Seas

Jonathan I. LunineCornell University

Outline

1. Occurrence and distribution2. Composition3. Longevity4. Astrobiology5. The future

Outline

1. Occurrence and distribution2. Composition3. Longevity4. Astrobiology5. The future

Ideas about surface methane and ethane on Titan were stimulated by Voyager 1 in 1980. Cassini discovered lakes and seas on Titan in 2006.

Aharonson et al., 2009

The lakes and seas are for the most part confined to high latitudes

The lakes and seas are part of Titan’s methane cycle.

Titan hydrocarbon reserves (surface-atmosphere)

1,000 gigatons is the estimated amount of oil, coal and gas energy companies have  in reserve on Earth

Lorenz et al. 2008

Mike Carroll

The seas are the third of three known carbon reservoirs

Outline

1. Occurrence and distribution2. Composition3. Longevity4. Astrobiology5. The future

ethane in Ontario Lacus (Brown et al. 2008)

We do not know the bulk ethane/methane/propane abundance

in the seas

Theoretical calculationCordier et al 2011

Outline

1. Occurrence and distribution2. Composition3. Longevity4. Astrobiology5. The future

Seasonal:Lora et al., 2011

Orbit precession

Aharonson et al

Sunlight received at thesurface.

Prime EquinoxSolstice

Turtle et al. 2011: shrinkage of Ontario Lacus over the late southern summer is consistent with evaporation

Seasonal effects are evident in the south but not the north.

Ligeia Mare may be part of a crustal liquid system that has persisted for some time, but not geologic time. Why are their seas today, and what is

their relation to the evolution of the interior?

100 km

Metallic Core

Salt-Rich OceanHP-Ice Layer

Ice/Hydrateshot

water

moves

through

hydrated

silicates

to oceanActively dehydrating rock core raises heat flux by 25-100%

The ethane sinks in the crust...into the ocean?

Density versus temperature of clathrate

Outline

1. Occurrence and distribution2. Composition3. Longevity4. Astrobiology5. The future

Chemical evolution on the road toward life would be a profound

scientific discovery

-CN

catalyst

HCN (produced in Titan’s high atmosphere)

Ligeia Mare’s equivalent of the chains from which proteins are built?

Simulation of HCN polymer (blue) seen against background of abiotic chemistry. Flight qualified mass specs can see this and other polymers indicative of chemical evolution on the way to life.

yielding

Outline

1. Occurrence and distribution2. Composition3. Longevity4. Astrobiology5. The future

T109 Feb 2015

T104 August 2014

Latitude line incr. are 5o

Lack of observed waves on the large seas may be seasonal

Prime XM

Solstice Mission

Now

Lorenz, Tokano and Newman, Planet. Space Sci., 2011

Sea surface• Winds on Titan have formed

dunes in many regions, apparent wave-modified beach at Ontario

• FLAT surfaces observed to date at Titan lakes

• GCM predictions are consistent with non-detection of waves

so far, but expect to observe waves ~ 2015-2017.• Tokano GCM predicts modest

winds during summer/fall TiME season.

VIMS and ISS images and spectra of the seas and lakes as the Sun climbs north

5 microns...VIMS

Titan Mare Explorer: A Discovery mission to float across Ligeia Mare, measuring the composition, depth and atmospheric interactions of a Titan sea.

Not selected for flight

TiME Science Objectives• Constrain sea composition

– Determine the chemistry of seas to constrain Titan's methane cycle, look for patterns indicative of chemical evolution in the abundance of constituents in the liquids and analyze noble gases. Instruments: Mass Spectrometer (NMS), Meteorology and Physical Properties Package (MP3).

• Constrain sea depth– Determine the depth of the Titan sea to determine sea volumes, and thus, organic

inventory. Instrument: MP3 (Sonar).• Measure sea surface properties

– Characterize physical properties of sea liquids and how they vary with depth and position. Instrument: MP3, NMS.

– Determine how the local meteorology over the seas ties to the global cycling of methane on seasonal and longer timescales. Instrument: MP3

– Analyze the nature of the sea surface (waves, foams, scums) and the state of the atmosphere above the sea. Instrument: Descent and Surface Imagers.

The 2020’s will be the lost decade for outer solar system exploration

Titan Mare Explorer: A Discovery mission to float across Ligeia Mare, measuring the composition, depth and atmospheric interactions of a Titan sea.

The Road goes ever on and on Down from the door where it began.Now far ahead the Road has gone, Let others follow it who can!Let them a journey new begin, But I at last with weary feetWill turn towards the lighted inn, My evening-rest and sleep to meet.

J.R.R. Tolkien

This is a Golden age of Planetary Exploration…but….

Budget deficits

Planetary

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