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
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