Life Outside the Habitable Zone? Astrobiology Workshop June 27, 2006 Astrobiology Workshop June 27, 2006

Life Outside the Habitable Zone?Life Outside the Habitable Zone?

Astrobiology WorkshopJune 27, 2006

Astrobiology WorkshopJune 27, 2006

Terrestrial Planet Region:Terrestrial Planet Region:Quick ReviewQuick Review

Terrestrial Planet Region:Terrestrial Planet Region:Quick ReviewQuick Review

MERCURYMERCURY

MOONMOON

VENUSVENUS

MARSMARS

XX Terrible Extremes of TemperatureTerrible Extremes of TemperatureNo Atmosphere, UV, Cosmic RaysNo Atmosphere, UV, Cosmic RaysLittle or No Volatiles, No LiquidsLittle or No Volatiles, No Liquids

Terrible Extremes of TemperatureTerrible Extremes of TemperatureNo Atmosphere, UV, Cosmic RaysNo Atmosphere, UV, Cosmic RaysLittle or No Volatiles, No LiquidsLittle or No Volatiles, No LiquidsBeen There, Done ThatBeen There, Done That

XX

Absurdly High TemperaturesAbsurdly High TemperaturesNo or Little Water No or Little Water Young Surface Young Surface No Fossil Record No Fossil Record

XX

?? Evidence for Liquid Water in PastEvidence for Liquid Water in PastPossible Environments for Life to Survive?Possible Environments for Life to Survive?Volatiles and Water Present NowVolatiles and Water Present Now

Gas and Ice Giant Planets:Gas and Ice Giant Planets:InteriorsInteriors

Gas and Ice Giant Planets:Gas and Ice Giant Planets:InteriorsInteriors

Gas Giant PlanetsGas Giant Planets Ice Giant PlanetsIce Giant Planets

Jupiter’s Interior:Jupiter’s Interior:More DetailMore Detail

Jupiter’s Interior:Jupiter’s Interior:More DetailMore Detail

XXXXX

Gas and Ice Giant Planets: Gas and Ice Giant Planets: AtmospheresAtmospheres

Gas and Ice Giant Planets: Gas and Ice Giant Planets: AtmospheresAtmospheres

Gas and Ice Giant Planets:Gas and Ice Giant Planets:Prospects for Life?Prospects for Life?

Gas and Ice Giant Planets:Gas and Ice Giant Planets:Prospects for Life?Prospects for Life?

Prospects for Life?Prospects for Life?

• There are ingredients for organic chemistry, and• Atmospheric layers exist with roughly Earth-like

Temperature & Pressure;• ButBut there are no solid surfaces (except ice

crystals) and no liquid water (except veryvery deep in UranusUranus and NeptuneNeptune),

• Violent winds and convective turbulence would mix any life-bearing gas quickly over extremes of T & P.

• Although the sunlight is very weak,• Internal heat is available.

• They are veryvery difficult to explore!

What about Moons of Planets?What about Moons of Planets?What about Moons of Planets?What about Moons of Planets?

For instance, the GalileanFor instance, the GalileanSatellites of JupiterSatellites of Jupiter

IoIo

EuropaEuropa

GanymedeGanymede

CallistoCallisto

Moons of the Outer Solar System:Moons of the Outer Solar System:Jupiter’s IoJupiter’s Io

Moons of the Outer Solar System:Moons of the Outer Solar System:Jupiter’s IoJupiter’s Io

Moons of the Outer Solar System:Moons of the Outer Solar System:Jupiter’s EuropaJupiter’s Europa

Moons of the Outer Solar System:Moons of the Outer Solar System:Jupiter’s EuropaJupiter’s Europa

Moons of the Outer Solar System:Moons of the Outer Solar System:Io and EuropaIo and Europa

Moons of the Outer Solar System:Moons of the Outer Solar System:Io and EuropaIo and Europa

Jupiter’s IoJupiter’s Io Is the most volcanicost volcanic object in the Solar

System due to Tidal heating Tidal heating caused by the gravitational

tug of war it experiences from Jupiter and its sister Galilean satellites.

Jupiter’s EuropaJupiter’s Europa Has similar but weaker tidal heating,weaker tidal heating, Has a young cracked water ice crustwater ice crust

perhaps only a few kilometers thick, and May have a warm ocean of liquid waterwarm ocean of liquid water

below the crust. Could there be life?life?

Tidal forces are difference forces.

Tidal Forces:Tidal Forces:Tides Raised on Earth by the Tides Raised on Earth by the

MoonMoon

Tidal Forces:Tidal Forces:Tides Raised on Earth by the Tides Raised on Earth by the

MoonMoonThe misaligned bulgesexert a small force onthe Moon that increasesthe size of its orbit, while friction in the bulges slows the Earth’s rotation.

Tidal Heating of a Moon:Tidal Heating of a Moon:Tides Raised by a Planet on its Tides Raised by a Planet on its

MoonMoon

Tidal Heating of a Moon:Tidal Heating of a Moon:Tides Raised by a Planet on its Tides Raised by a Planet on its

MoonMoon

Tidal heating occurs becauseIo and Europa’s orbits are Eccentric.

The orbits stay eccentric due to a three-way orbital resonance among the three moons Io, Europa, and Ganymede.

Effects of Tidal InteractionsEffects of Tidal InteractionsEffects of Tidal InteractionsEffects of Tidal Interactions

RotationRotation Rotation of moons become synchronizedsynchronized

with their orbits. They keep the same face toward the planet. The rotation of the planet is slowed down.

OrbitsOrbits Orbits of moons mostly evolve outwardoutward.

Internal “Tidal Heating”Internal “Tidal Heating” Eccentric orbits lead to periodic flexing of the

moon’s shape which heats the interior. Orbital resonances Orbital resonances with other moons can

maintain eccentric orbits and tidal heatingtidal heating.

Roche RadiusRoche RadiusRoche RadiusRoche Radius

Roche RadiusRoche Radius Objects held together

by their own gravity are shattered inside the Roche RadiusRoche Radius (about 2 Planet about 2 Planet RadiiRadii).

This is where most giant planet rings are.

Comet SL9Comet SL9 was tidally disruptedtidally disrupted within the Roche Radius of Jupiter and destroyed

Why doesn’t theWhy doesn’t theSpace Shuttle getSpace Shuttle getdisrupted? Why disrupted? Why

don’t we get don’t we get disrupted?disrupted?

Tidal Disruption:Tidal Disruption:Comet Shoemaker Levy 9Comet Shoemaker Levy 9

Tidal Disruption:Tidal Disruption:Comet Shoemaker Levy 9Comet Shoemaker Levy 9

Moons of the Outer Solar System:Moons of the Outer Solar System: Saturn’s Enceladus Saturn’s Enceladus


Saturn’s EnceladusSaturn’s EnceladusSmall icy moon (500 500 kmkm) in diameterYoung, crater-free surface regions with like those on EuropaOrbit resonance with DioneSouth polar hot spot and ice plumes Thin “atmosphere” of water vapor Subsurface ocean!?



Surface Temperatures on Surface Temperatures on EnceladusEnceladus

Ice Plumes from EnceladusIce Plumes from Enceladus

Moons of the Outer Solar System:Moons of the Outer Solar System:Saturn’s TitanSaturn’s Titan


Saturn’s TitanSaturn’s TitanThe atmosphere is denser than Earth’sdenser than Earth’s but very cold (100K100K) and mostly CH4 and N2 It is completely enshrouded in smog-smog-like cloudslike clouds Methane Methane acts like water there.There are few craters on the surface.Surface eroded by liquids but no oceans.

Moons of the Outer Solar System:Moons of the Outer Solar System:Titan’s AtmosphereTitan’s Atmosphere

Moons of the Outer Solar System:Moons of the Outer Solar System:Titan’s AtmosphereTitan’s Atmosphere



Moons of the Outer Solar System:Moons of the Outer Solar System:Movie of Huygen’s DecentMovie of Huygen’s Decent

Moons of the Outer Solar System:Moons of the Outer Solar System:Movie of Huygen’s DecentMovie of Huygen’s Decent

Show the movie outside Show the movie outside the ppt if there is time:the ppt if there is time:

http://saturn.jpl.nasa.gov/multimediahttp://saturn.jpl.nasa.gov/multimedia

Moons of the Outer Solar System:Moons of the Outer Solar System:“The Dunes of Titan”“The Dunes of Titan”

Moons of the Outer Solar System:Moons of the Outer Solar System:“The Dunes of Titan”“The Dunes of Titan”

Moons of the Outer Solar System:Moons of the Outer Solar System:Neptune’s TritonNeptune’s Triton

Moons of the Outer Solar System:Moons of the Outer Solar System:Neptune’s TritonNeptune’s Triton

Neptune’s TritonNeptune’s Triton

Extremely cold (< < 40K40K) objects made from volatile materials produce icy icy volcanism.volcanism.

Huge geysers of nitrogen!

Pluto and the Kuiper Belt Objects may look and act similarly.

Comparative Planetology:Comparative Planetology:Lessons LearnedLessons Learned

Comparative Planetology:Comparative Planetology:Lessons LearnedLessons Learned

Surfaces of Planets (or Moons)Surfaces of Planets (or Moons) Location, location, location… Size matters (for retaining an atmosphere). The star matters.

Overall, HoweverOverall, However There is an incredible diversity of worlds!!! There is an incredible diversity of worlds!!! Warm pockets or oceans of liquids plus organics

may exist in a variety of environments outsideoutside the classic Habitable ZoneHabitable Zone.

Even on Earth not all life requires starlight for an energy source. Sources of potentially life-giving energy may exist even in the cold outer reaches of our own and other planetary systems.

Beyond the Solar SystemBeyond the Solar SystemBeyond the Solar SystemBeyond the Solar System

Do We Live in a “Life-Friendly” Universe?Do We Live in a “Life-Friendly” Universe? Water and Carbon Chemistry are Everywhere!

• Hydrogen, Oxygen, Carbon, Nitrogen – 1st, 3rd, 4th, and 6th most abundant elements

• Organic Chemistry is found in– Interstellar gas clouds, comets, meteorites, outer

planet and moon atmospheres Physical Laws

• Copasetic Time Scales– Expansion rate of the Universe & stellar lifetimes

compatible with time to evolve complex life• Abundant Materials

– Even small changes in physical constants would cause little hydrogen or carbon to exist

• Huge Diversity of Environments

Documents

Life Outside the Habitable Zone? Astrobiology Workshop June 27, 2006 Astrobiology Workshop June 27, 2006