Observing a Lunar Observing a Lunar ImpactImpact

Karen J. Meech, AstronomerKaren J. Meech, AstronomerInstitute for AstronomyInstitute for AstronomyUniversity of Hawaii,University of Hawaii,

NASA Astrobiology InstituteNASA Astrobiology Institute

AAVSO ConferenceAAVSO ConferenceMay 4-6, 2006May 4-6, 2006

Impact PhysicsImpact Physics

Hypervelocity impactsHypervelocity impacts Collision v > 1-2 km/s Collision v > 1-2 km/s

where material where material behaves like a fluidbehaves like a fluid

Science usesScience uses Excavate hidden stuffExcavate hidden stuff Learn about impact Learn about impact

processesprocessesmitigationmitigation Scale depends onScale depends on

Target comp / porosityTarget comp / porosity Impactor compImpactor comp Angle of impactAngle of impact

Compression flash, hydrodynamic flow, melting, vapor)

Penetration(downward growth, reverse plume)

Excavation(ballistic flow in response to rarefaction)

Sand 60º(30% porosity)

Stages:Stages:

P. Schultz, Lab

Mission Science GoalsMission Science GoalsGoals: Goals: Chemical inventory of MoonChemical inventory of MoonConfirm origin modelsConfirm origin modelsLook for water/ice on the moonLook for water/ice on the moon

Earth in the HadeanEarth in the HadeanOceans & rocks formOceans & rocks form~4.4 billion yr ago~4.4 billion yr ago

>4.6 billion yr>4.6 billion yrISM dark cloudISM dark cloud

Protoplanetary diskProtoplanetary disk

Mission ProfileMission Profile

Launch 9/27/03 – Arianne 5Launch 9/27/03 – Arianne 5 Second use of Ion EngineSecond use of Ion Engine

Current flows across B field Current flows across B field creates E fieldcreates E field

E field accelerates Xe ionsE field accelerates Xe ions Solar panels: 1350 W powerSolar panels: 1350 W power Thrust: 0.07 NtThrust: 0.07 Nt Acceleration: 0.2 mm/sAcceleration: 0.2 mm/s22

Arrive 11/15/04Arrive 11/15/04 16 mo journey16 mo journey

TrajectoryTrajectory

Launch to an elliptical Launch to an elliptical Earth orbitEarth orbit

2 dy / wk burn 2 dy / wk burn gives gives increasing elliptical spiralincreasing elliptical spiral

200,000 km out, feel 200,000 km out, feel lunar gravitylunar gravity

Pass through L1 (50,000-Pass through L1 (50,000-60,000 from Moon) 60,000 from Moon) lunar capturelunar capture

Lunar polar orbitLunar polar orbit Gradually reduce size of Gradually reduce size of

orbitorbit

InstrumentsInstrumentsInstrumentInstrument ExperimentExperiment

EPDPEPDP Ion engine performanceIon engine performance

KaTE/RSISKaTE/RSIS Radio links to EarthRadio links to Earth

LaserLaser Earth telecommunicationsEarth telecommunications

OBANOBAN Onboard autonomous navOnboard autonomous nav

AMIEAMIE Ultra-compact visible cameraUltra-compact visible camera

SIRSIR Near IR spectrometerNear IR spectrometer

D-CIXSD-CIXS X-ray telescopeX-ray telescope

XSMXSM Monitor solar x-raysMonitor solar x-rays

SPEDESPEDE Solar wind wake measure.Solar wind wake measure.

Imaging ResultsImaging Results

DeGasparis – tectonic DeGasparis – tectonic rilles, range 1090 kmrilles, range 1090 km

Mayer-Bond cratersMayer-Bond craters Range 2685 kmRange 2685 km

Hopmann craterHopmann crater Aitkin basin edgeAitkin basin edge 88 km diam88 km diam

HumorumHumorum Highlands/mareHighlands/mare 4.1 Gy basin4.1 Gy basin

End of MissionEnd of Mission Exhaust Xe fuel Exhaust Xe fuel lunar impact lunar impact

Impact far side on 8/17/06Impact far side on 8/17/06 Science RationaleScience Rationale Effects of space weatheringEffects of space weathering Physics and diagnostics of low velocity impactsPhysics and diagnostics of low velocity impacts

Extended MissionExtended Mission 6/26/06 6/26/06 hydrazine thruster maneuvers hydrazine thruster maneuvers Add 12 m/s velocity Add 12 m/s velocity extend lifetime extend lifetime Impact 9/3/06 at 2:00 UT on near sideImpact 9/3/06 at 2:00 UT on near side The ImpactThe Impact

Mass:Mass: 290 kg (200 Al from body)290 kg (200 Al from body) Velocity: Velocity: 2 km/sec2 km/sec Where:Where: 3636oo S, 44 S, 44oo W W

Lunar ProspectorLunar Prospector

Discovery ($63M)Discovery ($63M) Launch 1/6/98Launch 1/6/98 Lunar arrival: 4 dysLunar arrival: 4 dys

ScienceScience Water at the poles?Water at the poles? 1st entire surface gravity map1st entire surface gravity map Local B field measuredLocal B field measured 11stst global maps of lunar comp global maps of lunar comp

Aitkin basin Aitkin basin 2500km diameter2500km diameter 12 km deep12 km deep Permanently shadowedPermanently shadowed T < 100KT < 100K

Water at the PolesWater at the Poles

Clementine – bistatic radarClementine – bistatic radar Lunar Prospector – N specLunar Prospector – N spec

High E interactions High E interactions rays, rays, neutronsneutrons

Ratio of high E and thermal n Ratio of high E and thermal n depends on amt of Hdepends on amt of H

LP ImpactLP Impact Controlled crash nr S poleControlled crash nr S pole

Crater 4 km deepCrater 4 km deep Impact angle 6.5Impact angle 6.5oo, , 1.7 km/s, mass 161 kg1.7 km/s, mass 161 kg Ejecta could rise 30 kmEjecta could rise 30 km

Search for lunar waterSearch for lunar water To produce 18 kg waterTo produce 18 kg water Heated to 400 K, Vapor visible 4 Heated to 400 K, Vapor visible 4

sec latersec later

LP Impact ResultsLP Impact Results

LP hit the expected craterLP hit the expected crater No detection of water or OH (Keck, HST, McDonald)No detection of water or OH (Keck, HST, McDonald)

Not enough E to liberate HNot enough E to liberate H22O from hydrated mineralsO from hydrated minerals

No enhanced Na, HCN or CNo enhanced Na, HCN or C22

No dust observedNo dust observed

OH Image from McDonald ObstyOH Image from McDonald Obsty HST UV spectra – search for OHHST UV spectra – search for OH

SMART 1 PredictionsSMART 1 Predictions Timing UncertaintyTiming Uncertainty +/- 1 orbit+/- 1 orbit Previous perilune alt 400mPrevious perilune alt 400m

Impact regimeImpact regime Strength dominatedStrength dominated Si should not meltSi should not melt 80% cold ejecta80% cold ejecta

Crater sizeCrater size 5-10 m5-10 m 30-100 tons of dust30-100 tons of dust

Brightness of flashBrightness of flash 50% E in thermal 50% E in thermal mag 7.4 mag 7.4 More likely More likely 16 16 Duration 20 millisecDuration 20 millisec

SpectraSpectra Emission from s/c Emission from s/c

volatiles Nvolatiles N22, H, H44 NH NH33

Near IR Near IR mineral mineral propertiesproperties

Dust PlumeDust Plume Visible from EarthshineVisible from Earthshine Dust 15 Dust 15 mm 1% reaches sunlight 1% reaches sunlight

mag 11.5mag 11.5

SMART 1 vs. LPSMART 1 vs. LP

Better than Lunar ProspectorBetter than Lunar ProspectorDirect view of impact site, dark partDirect view of impact site, dark part Illumination by EarthshineIllumination by EarthshineMore Energy (< 1 kg meteorite @ 40 km/s)More Energy (< 1 kg meteorite @ 40 km/s)

Lunar ProsLunar Pros SMART 1SMART 1

Moon phaseMoon phase Full + 2 dyFull + 2 dy Full – 4 dyFull – 4 dy

MassMass 161 kg161 kg 290 kg290 kg

VelocityVelocity 1.7 km/s1.7 km/s 2.0 km/s2.0 km/s

Impact angleImpact angle 6.5 deg6.5 deg grazinggrazing

Jul 6/7, Aug Jul 6/7, Aug 3/4 or 4/53/4 or 4/5

Similar phase, Similar phase, viewview

Aug 6/7Aug 6/7 Overfly target Overfly target sites, Earth obssites, Earth obs

Sep 2Sep 2 RehearsalRehearsal

Sep 3Sep 3 ImpactImpact

Sep 4-17Sep 4-17 Image ejecta Image ejecta blanketsblankets

TimelinesTimelines

Will we see it?Will we see it? Lunar meteorite Lunar meteorite

impacts are seenimpacts are seen Ogawamura ObstyOgawamura Obsty

Aug 11, 2004, 18:28:27Aug 11, 2004, 18:28:27 PerseidsPerseids 99thth mag, 1/30 s duration mag, 1/30 s duration Confirmed by 2 othersConfirmed by 2 others

DiscoveryDiscovery 0.6m newtonian + TV 0.6m newtonian + TV

cameracamera

ConfirmationsConfirmations 0.6 m + TV0.6 m + TV 0.16m + TV0.16m + TV

World PlansWorld PlansEurope/AfricaEurope/Africa AmericaAmerica HawaiiHawaii

Optical imagingOptical imaging SALTSALT NTTNTT

Optical spectraOptical spectra TNGTNG VLTVLT

NIR imagingNIR imaging VLTVLT IRTFIRTF

NIR AONIR AO VLTVLT Gemini Gemini

ThermalThermal VLTVLT SubaruSubaru