Origin of EarthOrigin of Earth’’s Oceanss Oceans

Karen Karen MeechMeech,,Session #29 Session #29 –– Tues 1/18/05 Tues 1/18/05

D/H Units TranslationD/H Units Translation

Absolute abundances harder to measureAbsolute abundances harder to measure Measure relative to a standardMeasure relative to a standard

S.M.O.W. for D/H = 155.76 x 10S.M.O.W. for D/H = 155.76 x 10-6-6

DefinitionDefinition δδ = D/ = D/HHsamplesample –– D/H D/HSMOWSMOW

D/H D/HSMOWSMOW

Example:Example: LL3 meteorites: D/H = 76 LL3 meteorites: D/H = 76 –– 457 x 10 457 x 10-6-6

δδDDSMOWSMOW = -512 = -512oooo//oo to +1934 to +1934oooo//oo

X 1000 per milX 1000 per mil

Origin of EarthOrigin of Earth’’ssWaterWater

Most Most imptimpt debate / debate /controversy in SS formcontroversy in SS form

Oceans are enriched inOceans are enriched inDeuteriumDeuterium Comets brought someComets brought some

(10-30%)(10-30%) Isotopic Tracers Isotopic Tracers –– D/H D/H

Earth ~ 16 x10Earth ~ 16 x10-5-5

Solar System ~ 2.5x10Solar System ~ 2.5x10-5-5

CometsComets ~ 30 x10 ~ 30 x10-5-5

Iceland Iceland –– Hawaii Hawaii

The D/H ratio in comets is The D/H ratio in comets is notnot well established well established The reference to Earth is SMOW The reference to Earth is SMOW –– how does this how does this

relate to the primordial water?relate to the primordial water?

D/H IssuesD/H Issues Original D/H Original D/H –– set in big bang set in big bang

Formation of molecules in cold cloudsFormation of molecules in cold clouds Isotopic enrichment in cold interstellar cloudsIsotopic enrichment in cold interstellar clouds

Ion-Molecule reactionsIon-Molecule reactions PlanetesimalPlanetesimal formation formation –– fractionation fractionation

Comet formation scenariosComet formation scenarios PlanetesimalPlanetesimal delivery to Earth delivery to Earth

Sources of WaterSources of Water D/H comet measurementsD/H comet measurements Fractionation processes on Earth . . . ?Fractionation processes on Earth . . . ?

Deep Mantle Water?Deep Mantle Water? Measurements & InstrumentationMeasurements & Instrumentation

The Interstellar MediumThe Interstellar Medium Cold clouds Cold clouds hot cores hot cores

T ~ 10-300KT ~ 10-300K n ~ 3 x 10n ~ 3 x 1044 cm cm-3-3

Grains Grains sites of sites ofmolecule formationmolecule formation Collisions Collisions sticking sticking Mobility of D and H is keyMobility of D and H is key

Element FormationElement Formation H, He form in big bangH, He form in big bang Heavier elements Heavier elements dust dust

processed inside starsprocessed inside stars

D/H Measurements in Diffuse ISMD/H Measurements in Diffuse ISM Lyman Lyman αα absorption absorption

toward several starstoward several stars Local valueLocal value

D/D/HHavgavg ~ 1.6 x 10 ~ 1.6 x 10-5-5

Range: 1.4-2.2 x 10Range: 1.4-2.2 x 10-5-5

[[δδDD = -910 = -910 - -858858oooo//oo]]

ProtosolarProtosolar Value Value D/H = 2.5 x 10D/H = 2.5 x 10-5-5

[[δδDD = -839 = -839oooo//oo]] D/H at time of SS formD/H at time of SS form 33He/He/44He in solar wind +He in solar wind +

D D 33He modelsHe models Giant planets + modelsGiant planets + models

ISM D/H FractionationISM D/H Fractionation–– Ion Molecule Ion Molecule

ReactionsReactions

CHCH44

CC22HH22

CC22HH44

CC22HH66

HH22OO

HH22SS

NHNH33

COCO22

COCO

CHCH33OHOH

CC22HH55OHOH

CC22HH33COCHCOCH33HH22COCO

CHCH33CHOCHO

HCOOHHCOOH

CHCH33COOHCOOH

Gas phase reactionsGas phase reactions D & H D & H –– slight mass difference slight mass difference Closer E levels Closer E levels D favored in D favored in

kineticskinetics 1322 reactions / 107 species1322 reactions / 107 species Energy levels not known forEnergy levels not known for

polyatomic moleculespolyatomic molecules Reaction rates strongly TReaction rates strongly T

dependent dependent time dependent time dependent Many moleculesMany molecules Chemical modelsChemical models CanCan’’t decouplet decouple

simple moleculessimple molecules

D EnrichmentD Enrichment Primary Gas Phase Deuterium ReactionsPrimary Gas Phase Deuterium Reactions

Certain reverse reactions in isotopic exchange are stronglyCertain reverse reactions in isotopic exchange are stronglyinhibited at low Tinhibited at low T

Results in preference for formation of certain Results in preference for formation of certain deuterateddeuterated species species Rate coefficients, k cmRate coefficients, k cm33 s s-1-1

2.0(-10)2.0(-10)9.3(-11)9.3(-11)8.8(-12)8.8(-12)3.6(-18)3.6(-18)HH22DD++ + H + H22 H H33++ + HD + HD

1.4(-09)1.4(-09)1.5(-09)1.5(-09)1.5(-09)1.5(-09)1.7(-09)1.7(-09)HH33++ + HD + HD H H22DD++ + H + H22

70K70K50K50K30K30K10K10KReactionReaction

Gas-Grain ReactionsGas-Grain Reactions Through accretion, D-molecules not destroyed as fastThrough accretion, D-molecules not destroyed as fast This leads to large This leads to large deuterateddeuterated molecule enhancement molecule enhancement

ISM Core MeasurementsISM Core Measurements W33aW33a

D/H ~ (40-150) x 10D/H ~ (40-150) x 10-5 -5 [[δδDD=+1568=+1568++86308630oooo//oo]]

Hot coresHot cores E barriers inhibiting reverse reactionsE barriers inhibiting reverse reactions

overcomeovercome Accretion/surface chemistryAccretion/surface chemistry Evaporation of grain mantlesEvaporation of grain mantles Preserved for ~ 10Preserved for ~ 1044 yr yr

DeuterationDeuteration much stronger in low much stronger in low mass stars mass stars

Orders of magnitude higherOrders of magnitude higher

PlanetesimalPlanetesimal formation formation

Collapse of interstellar cloudCollapse of interstellar cloud Center collapses faster Center collapses faster flattened disk flattened disk Grain Grain infallinfall passes shock front passes shock front sublimation, sublimation, recondenserecondense Turbulent mixing of gas / solids Turbulent mixing of gas / solids radial transport radial transport Eventual gravitational clumping Eventual gravitational clumping planet building planet building Comets: how much ISM material is preserved Comets: how much ISM material is preserved –– is the diff is the diff

between SP and LP comets important for D/H?between SP and LP comets important for D/H?

Comets: Archaeological RemnantsComets: Archaeological Remnants KuiperKuiper Belt & Belt & OortOort Cloud reservoir Cloud reservoir Perturbations Perturbations close to sun close to sun Activity developsActivity develops

Km-scale nucleusKm-scale nucleus Coma ~ 10Coma ~ 1055 km km Tail ~ 10Tail ~ 1066-10-1077 km km

ISM Alteration in Nebula?ISM Alteration in Nebula?

Re-equilibration of D/HRe-equilibration of D/H Need heatNeed heat

k(Tk(T) drops 5 orders ) drops 5 orders magmag from T=1000 from T=1000 300K 300K

Need reservoir of Hydrogen gasNeed reservoir of Hydrogen gas No isotopic exchange between gas / solidsNo isotopic exchange between gas / solids

Radial mixing of gasRadial mixing of gas Reset D/H only in warm inner nebulaReset D/H only in warm inner nebula How far out did turbulence extend?How far out did turbulence extend?

Chemical heterogeneitiesChemical heterogeneities HH22CO in 1P/HalleyCO in 1P/Halley

Crystalline silicatesCrystalline silicates Requires high T (> 800K)Requires high T (> 800K)

KBO dynamics KBO dynamics –– planet planetmigrationmigration

Evidence for Radial MixingEvidence for Radial Mixing

Comet Isotopic MeasurementsComet Isotopic Measurements HDO @ 464.925 GHzHDO @ 464.925 GHz

High dry site: Mauna KeaHigh dry site: Mauna Kea Relate line strength to amtRelate line strength to amt

Excitation modelsExcitation models CollisionalCollisional excitation & LTE excitation & LTE Fluorescence Fluorescence –– balance balance

between excitation &between excitation &vibrationalvibrational-rotation decay-rotation decay

Measure gas temperatureMeasure gas temperature

Measure QMeasure QHH22OO separately separately IR IR –– ro-vibrationalro-vibrational bands bands UV (IUE) UV (IUE) –– OH + models OH + models Ground Ground –– narrow band OH narrow band OH Lyman Lyman αα (SOHO) + models (SOHO) + models

D/H in CometsD/H in Comets

TBDTBDSub-mmSub-mmTempelTempel 1 133 +/- 833 +/- 8Sub-mmSub-mmHale Hale BoppBopp

TBDTBDRosetta Rosetta –– in situ in situWirtanenWirtanen

29 +/- 1029 +/- 10Sub-mmSub-mmHyakutakeHyakutake31.6 +/- 3.431.6 +/- 3.4Neutral mass specNeutral mass specHalleyHalley30.8 +/- 430.8 +/- 4Ion mass specIon mass specHalleyHalley

Value x 10Value x 10-5-5MethodMethodCometComet

All measured so far are from All measured so far are from OortOort cloud cloud Prediction: KBO more enriched (lessPrediction: KBO more enriched (less

mixing in nebula)mixing in nebula) Sub-mm measurements very indirectSub-mm measurements very indirect

D/H Preserved During Sublimation?D/H Preserved During Sublimation?

Sublimation of HDO and HSublimation of HDO and H22O from separate frontsO from separate fronts Nucleus is porousNucleus is porous Vapor pressures are equal (lab Vapor pressures are equal (lab measmeas)) ρρHDOHDO < < ρρHH22OO HDO front moves inward faster HDO front moves inward faster HDO HDO

flux decreases fasterflux decreases faster Steady state eventually reached Steady state eventually reached D/H D/H measmeas = D/H = D/H

nucleusnucleus Far from steady state D/H can be a factor of 2 highFar from steady state D/H can be a factor of 2 high Steady state near q, different if far from qSteady state near q, different if far from q

Meteorite D/H MeasurementsMeteorite D/H Measurements MeteoritesMeteorites

Water-rich minerals in someWater-rich minerals in some Form within 1-2 Form within 1-2 MyrMyr of SS form of SS form Evidence for heating & aqueousEvidence for heating & aqueous

alterationalteration

D/H MeasurementsD/H Measurements ChondrulesChondrules in LL3 D-rich meteorites: in LL3 D-rich meteorites:

(7-45) x 10(7-45) x 10-5-5

[[δδDD = -550 = -550+1+1889889oooo//oo]] ChondritesChondrites

(12-30) x 10(12-30) x 10-5-5

[[δδDD = -229 = -229++926926oooo//oo]]

D/H x 10D/H x 10-5-5

EarthEarth

Mars Mars –– SNC Meteorites SNC Meteorites

Atmospheric water:Atmospheric water: D/H = 81 x 10D/H = 81 x 10-5-5 ( (δδDD=+4200=+4200oooo//oo)) May be enriched because ofMay be enriched because of

preferential H preferential H atmatm escape escape Jeans EscapeJeans Escape

High E tail of Maxwell v High E tail of Maxwell v distndistnescapesescapes

Mars D/H fractionationMars D/H fractionation Loss of 2.7x10Loss of 2.7x1088 cm cm-2-2ss-1-1 on Earth, on Earth,

small compared to reservoirsmall compared to reservoir Loss on Mars of 2.4x10Loss on Mars of 2.4x1088 cm cm-2-2ss-1-1

Reservoir unknownReservoir unknown

Log of water in Mars crust todayLog of water in Mars crust today(H(H11) versus early Mars, (H) versus early Mars, (Hoo) for) forD/H ratios D/H ratios wrtwrt SMOW of 2.6 & 5.2 SMOW of 2.6 & 5.2

Dynamical Delivery ofDynamical Delivery ofMeteoritic MaterialMeteoritic Material

Dynamical models (Dynamical models (MorbidelliMorbidelli)) delivery in few impacts (small number statistics)delivery in few impacts (small number statistics) Secular resonances & planet migration + gas drag:Secular resonances & planet migration + gas drag:

delivers Hdelivers H22O-rich asteroids to EarthO-rich asteroids to Earth Models show only 2-20% of Models show only 2-20% of cometarycometary bodies were bodies were

delivered to Earthdelivered to Earth

Problem with Nobel gas abundancesProblem with Nobel gas abundances Earth has too much Earth has too much NeNe to come from asteroids, but to come from asteroids, but

maybe not cometsmaybe not comets

Summary of D/H MeasurementsSummary of D/H Measurements

> +1568> +1568

+926+926

-550 -550 +1889 +1889

00

-839-839

-910 -910 -858-858

[[δδDD oooo//oo]]

> 40-50 x 10> 40-50 x 10-5-5Molecular cloudsMolecular clouds/ hot cores/ hot cores

30 x 1030 x 10-5-5CometsComets

7-45 x 107-45 x 10-5-5MeteoritesMeteorites

16 x 1016 x 10-5-5SMOWSMOW

2.5 x 102.5 x 10-5-5ProtosolarProtosolar Nebula Nebula

1.4-2.2 x 101.4-2.2 x 10-5-5Diffuse ISMDiffuse ISM

D/HD/HSourceSource

Status of D/H MeasurementsStatus of D/H Measurements

We donWe don’’t really know comet D/H for more than one typet really know comet D/H for more than one type Meteorite measurements have wide rangeMeteorite measurements have wide range

Dynamics of delivery?Dynamics of delivery? Nobel gas abundances?Nobel gas abundances?

Does SMOW represent the primordial water on Earth?Does SMOW represent the primordial water on Earth?

????

EarthEarth’’s Juvenile Water?s Juvenile Water?

Are there sources of DeepAre there sources of DeepMantle primordial water?Mantle primordial water?

What are fractionationWhat are fractionationprocesses on Earth for D/H?processes on Earth for D/H? Lack of re-equilibration: noLack of re-equilibration: no

source of Hsource of H How to assess contaminationHow to assess contamination

in mantle waterin mantle watermeasurements?measurements?

If water is delivered duringIf water is delivered duringimpact impact –– is the D/H reset? is the D/H reset?

How to Access Primordial Water?How to Access Primordial Water? Glacier & GeothermalGlacier & Geothermal

systemssystems Gas phase measurements?Gas phase measurements? Take Advantage of drillingTake Advantage of drilling

High T rock phasesHigh T rock phasessurviving transportsurviving transport Olivine, pyroxene, diamondOlivine, pyroxene, diamond 33He/He/44He in He in phenocrystsphenocrysts Xenoliths: Xenoliths: δδDD = -40 to -95 = -40 to -95oooo//oo

Fractionation Processes on EarthFractionation Processes on Earth Evaporation / condenseEvaporation / condense

Light molecules enriched inLight molecules enriched invapor phasevapor phase

Kinetic effectsKinetic effects Rate of chemical reactionRate of chemical reaction

related to massrelated to mass DiffusionDiffusion

Light isotopes more mobileLight isotopes more mobile PressurePressure

Hydrous minerals D/HHydrous minerals D/Hfractionationfractionation

Chemical compositionChemical composition Nature of chemical bonds Nature of chemical bonds ––

high vibration high vibration ff prefer heavier prefer heavierisotopesisotopes

Crystal structureCrystal structure Heavy isotopes concentrateHeavy isotopes concentrate

in more closely packedin more closely packedstructuresstructures

MORB waterMORB water Homogeneous Homogeneous wrtwrt % water % water Remixed into source orRemixed into source or

uniform degassinguniform degassing Hot spots and xenoliths Hot spots and xenoliths

significant hydration in mantlesignificant hydration in mantle Upper mantle *may* containUpper mantle *may* contain

primordial Hprimordial H22OO

HydrosphereHydrosphere UV photochemistryUV photochemistry Impact degassingImpact degassing subductionsubduction

Deep Drilling ProjectsDeep Drilling Projects HSDP HSDP –– Hilo Hilo

4 km (ongoing)4 km (ongoing) Isotopic data Isotopic data vsvs time: plume time: plume

geochemistrygeochemistry

IDDP IDDP –– Iceland Iceland 5 km (start 11/04)5 km (start 11/04) Extraction of Energy &Extraction of Energy &

chemicals 400-600chemicals 400-600ooCC

InstrumentsInstruments Small down-hole mass specSmall down-hole mass spec Boreholes 4Boreholes 4”” diamdiam

Hawaii ScientificHawaii ScientificDrilling ProjectDrilling Project

Continuous samples fromContinuous samples fromMKO flowsMKO flows Learn how mantle plumesLearn how mantle plumes

originate & magma tooriginate & magma tosurfacesurface

Drill from 1000 -700,000 yrDrill from 1000 -700,000 yr(20,000 ft)(20,000 ft)

Zoned plumeZoned plume Core from deep mantleCore from deep mantle

Iceland Deep Drilling ProjectIceland Deep Drilling Project Plan (economic)Plan (economic)

Depth of geothermalDepth of geothermalresourcesresources

5 km well in 5 km well in RekjanesRekjanespeninsula (2007-8)peninsula (2007-8)

3 wells, 15 yr 3 wells, 15 yr –– KreplaKrepla

Problems for primordialProblems for primordialwater searchwater search Rocks are very permeableRocks are very permeable Fluid origins Fluid origins –– seawater? seawater? Water-rock exchange?Water-rock exchange? Permeability at depthPermeability at depth

unknownunknown

Suggested tacticsSuggested tactics Gas inclusions inGas inclusions in

phenocristsphenocrists Sampling new volcanicSampling new volcanic

plumesplumes Gas samples disappearGas samples disappear

quicklyquickly

GrimsvotnGrimsvotn Eruption Eruption –– Nov 2004 Nov 2004

Does a Habitable World RequireDoes a Habitable World Requirean Asteroid Belt?an Asteroid Belt?

Implications for terrestrial planet HImplications for terrestrial planet H22O in otherO in otherSS SS require an asteroid belt? require an asteroid belt? OortOort cloud? cloud?

Discussion Nordic Discussion Nordic CtrCtr for for VolcanologyVolcanology::Karl Karl GronvoldGronvold, , NielsNiels OskarssonOskarsson

Look for D/H in high TLook for D/H in high Tphasesphases H released from deepH released from deep

sources from breakdownsources from breakdownof hydridesof hydrides

Interaction with C Interaction with C CH CH44 At high T (1500K) noAt high T (1500K) no

fractionationfractionation Gases trapped inGases trapped in

inclusion in inclusion in spinelsspinels,,olivinesolivines, diamonds, diamonds

MeasurementsMeasurements H with ion beams (SIMS)H with ion beams (SIMS) H measurement trickyH measurement tricky

(need clean system)(need clean system) D very challengingD very challenging

33He/He/44He anomalies He anomalies –– in inIceland and HawaiiIceland and Hawaii

QuestionsQuestions Timescale for planetaryTimescale for planetary

chemical fractionation &chemical fractionation &core formation?core formation?

Discussion Nordic Discussion Nordic CtrCtr for for VolcanologyVolcanology::Karl Karl GronvoldGronvold, , NielsNiels OskarssonOskarsson

SurtseySurtsey gas analysis gas analysis Rare gas workRare gas work Probably recycledProbably recycled

seawaterseawater

Helium workHelium work Primordial He high inPrimordial He high in

NW & central IcelandNW & central Iceland Geothermal waterGeothermal water

Isotopic work IcelandIsotopic work Iceland Mostly meteoricMostly meteoric Except Except ReykjanesReykjanes

peninsula (peninsula (δδDD=-20%)=-20%) Rocks very permeableRocks very permeable