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Observing a Lunar Impact Karen J. Meech, Astronomer Institute for Astronomy University of Hawaii, NASA Astrobiology Institute AAVSO Conference May 4-6,

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Presentation on theme: "Observing a Lunar Impact Karen J. Meech, Astronomer Institute for Astronomy University of Hawaii, NASA Astrobiology Institute AAVSO Conference May 4-6,"— Presentation transcript:

1 Observing a Lunar Impact Karen J. Meech, Astronomer Institute for Astronomy University of Hawaii, NASA Astrobiology Institute AAVSO Conference May 4-6, 2006

2 Impact Physics Hypervelocity impacts Hypervelocity impacts Collision v > 1-2 km/s where material behaves like a fluid Collision v > 1-2 km/s where material behaves like a fluid Science uses Science uses Excavate hidden stuff Excavate hidden stuff Learn about impact processes mitigation Learn about impact processes mitigation Scale depends on Scale depends on Target comp / porosity Target comp / porosity Impactor comp Impactor comp Angle of impact Angle 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: P. Schultz, Lab

3 Mission Science Goals Goals: Goals: Chemical inventory of Moon Chemical inventory of Moon Confirm origin models Confirm origin models Look for water/ice on the moon Look for water/ice on the moon Earth in the Hadean Oceans & rocks form ~4.4 billion yr ago >4.6 billion yr ISM dark cloud Protoplanetary disk

4 Mission Profile Launch 9/27/03 – Arianne 5 Launch 9/27/03 – Arianne 5 Second use of Ion Engine Second use of Ion Engine Current flows across B field creates E field E field accelerates Xe ions Solar panels: 1350 W power Thrust: 0.07 Nt Acceleration: 0.2 mm/s 2 Arrive 11/15/04 Arrive 11/15/04 16 mo journey

5 Trajectory Launch to an elliptical Earth orbit Launch to an elliptical Earth orbit 2 dy / wk burn gives increasing elliptical spiral 2 dy / wk burn gives increasing elliptical spiral 200,000 km out, feel lunar gravity 200,000 km out, feel lunar gravity Pass through L1 (50, ,000 from Moon) lunar capture Pass through L1 (50, ,000 from Moon) lunar capture Lunar polar orbit Lunar polar orbit Gradually reduce size of orbit Gradually reduce size of orbit

6 InstrumentsInstrumentExperimentEPDP Ion engine performance KaTE/RSIS Radio links to Earth Laser Earth telecommunications OBAN Onboard autonomous nav AMIE Ultra-compact visible camera SIR Near IR spectrometer D-CIXS X-ray telescope XSM Monitor solar x-rays SPEDE Solar wind wake measure.

7 Imaging Results DeGasparis – tectonic rilles, range 1090 km DeGasparis – tectonic rilles, range 1090 km Mayer-Bond craters Mayer-Bond craters Range 2685 km Range 2685 km Hopmann crater Hopmann crater Aitkin basin edge Aitkin basin edge 88 km diam 88 km diam Humorum Humorum Highlands/mare Highlands/mare 4.1 Gy basin 4.1 Gy basin

8 End of Mission Exhaust Xe fuel lunar impact Exhaust Xe fuel lunar impact Impact far side on 8/17/06 Impact far side on 8/17/06 Science Rationale Science Rationale Effects of space weathering Effects of space weathering Physics and diagnostics of low velocity impacts Physics and diagnostics of low velocity impacts Extended Mission Extended Mission 6/26/06 hydrazine thruster maneuvers 6/26/06 hydrazine thruster maneuvers Add 12 m/s velocity extend lifetime Add 12 m/s velocity extend lifetime Impact 9/3/06 at 2:00 UT on near side Impact 9/3/06 at 2:00 UT on near side The Impact The Impact Mass:290 kg (200 Al from body) Mass:290 kg (200 Al from body) Velocity: 2 km/sec Velocity: 2 km/sec Where:36 o S, 44 o W Where:36 o S, 44 o W

9 Lunar Prospector Discovery ($63M) Discovery ($63M) Launch 1/6/98 Launch 1/6/98 Lunar arrival: 4 dys Lunar arrival: 4 dys Science Science Water at the poles? Water at the poles? 1st entire surface gravity map 1st entire surface gravity map Local B field measured Local B field measured 1 st global maps of lunar comp 1 st global maps of lunar comp Aitkin basin Aitkin basin 2500km diameter 2500km diameter 12 km deep 12 km deep Permanently shadowed Permanently shadowed T < 100K T < 100K

10 Water at the Poles Clementine – bistatic radar Clementine – bistatic radar Lunar Prospector – N spec Lunar Prospector – N spec High E interactions rays, neutrons High E interactions rays, neutrons Ratio of high E and thermal n depends on amt of H Ratio of high E and thermal n depends on amt of H

11 LP Impact Controlled crash nr S pole Controlled crash nr S pole Crater 4 km deep Impact angle 6.5 o, 1.7 km/s, mass 161 kg Ejecta could rise 30 km Search for lunar water Search for lunar water To produce 18 kg water Heated to 400 K, Vapor visible 4 sec later

12 LP Impact Results LP hit the expected crater LP 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 H 2 O from hydrated minerals No enhanced Na, HCN or C 2 No enhanced Na, HCN or C 2 No dust observed No dust observed OH Image from McDonald Obsty HST UV spectra – search for OH

13 SMART 1 Predictions Timing Uncertainty Timing Uncertainty +/- 1 orbit +/- 1 orbit Previous perilune alt 400m Previous perilune alt 400m Impact regime Impact regime Strength dominated Strength dominated Si should not melt Si should not melt 80% cold ejecta 80% cold ejecta Crater size Crater size 5-10 m 5-10 m tons of dust tons of dust Brightness of flash Brightness of flash 50% E in thermal mag % E in thermal mag 7.4 More likely 16 More likely 16 Duration 20 millisec Duration 20 millisec Spectra Spectra Emission from s/c volatiles N 2, H 4 NH 3 Emission from s/c volatiles N 2, H 4 NH 3 Near IR mineral properties Near IR mineral properties Dust Plume Dust Plume Visible from Earthshine Visible from Earthshine Dust 15 m Dust 15 m 1% reaches sunlight mag % reaches sunlight mag 11.5

14 SMART 1 vs. LP Better than Lunar Prospector Better than Lunar Prospector Direct view of impact site, dark part Direct view of impact site, dark part Illumination by Earthshine Illumination by Earthshine More Energy (< 1 kg 40 km/s) More Energy (< 1 kg 40 km/s) Lunar Pros SMART 1 Moon phase Full + 2 dy Full – 4 dy Mass 161 kg 290 kg Velocity 1.7 km/s 2.0 km/s Impact angle 6.5 deg grazing Jul 6/7, Aug 3/4 or 4/5 Similar phase, view Aug 6/7 Overfly target sites, Earth obs Sep 2 Rehearsal Sep 3 Impact Sep 4-17 Image ejecta blankets Timelines

15 Will we see it? Lunar meteorite impacts are seen Lunar meteorite impacts are seen Ogawamura Obsty Ogawamura Obsty Aug 11, 2004, 18:28:27 Perseids 9 th mag, 1/30 s duration Confirmed by 2 others Discovery Discovery 0.6m newtonian + TV camera 0.6m newtonian + TV camera Confirmations Confirmations 0.6 m + TV 0.6 m + TV 0.16m + TV 0.16m + TV

16 World Plans Europe/AfricaAmericaHawaii Optical imaging SALTNTT Optical spectra TNGVLT NIR imaging VLTIRTF NIR AO VLTGemini ThermalVLTSubaru


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