Lyman Alpha Mapping Project (LAMP) Volatile Studies: PSR Water Frost, Lunar Atmosphere, and LCROSS Plume Observations

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1 Lyman Alpha Mapping Project (LAMP) Volatile Studies: PSR Water Frost, Lunar Atmosphere, and LCROSS Plume Observations Kurt Southwest Research Inst. Nov. 17, 2009 THE LAMP TEAM: G.R. Gladstone, S. A. Stern, K.D., J.Wm.. Parker, D.C. Slater, M.W. Davis, R.K. Black, T.K. Greathouse, M.H. Versteeg, K. B. Persson, D.E. Kaufmann, A.F. Egan, P. Miles, J. Mukherjee, P.D. Feldman, D.M. Hurley, W.R. Pryor, and A.R. Hendrix 1

2 Lunar Water Formation/Delivery Vondrak & Crider, American Scientist, 2003 Possible Sources Include: Solar wind protons react with Moon rocks to form H 2 O Comets periodically deliver large amounts of H 2 O Remaining primordial water 2

3 Lunar Atmosphere Transport Sodium Corona: Potter et al., JGR, 2000 Vondrak & Crider, American Scientist,

4 Lunar Water Ice Trapping Volatiles in the cold PSRs are very stable to sublimation Only photolyzed by UV star light and interplanetary hydrogen light Solar wind ion impact dissociation Mixing of ice into the soil by micrometeorite bombardment is thought to bury ice Protects water from loss by UV photolysis Does this process actually happen? 4

5 LRO-LAMP Instrument LAMP: UV Spectrograph Mass: 6.08 kg Power: 4.8 W λ Range: nm 5

6 LAMP Measurements Observe nadir and use a push-broom motion to scan the slit on the surface to create 2D maps Sensitive enough to view the reflected signal of starlight and Lyman-alpha sky-glow on the nightside and in PSRs 6

7 How can we see into the permanently shadowed regions? The sky is aglow in Lymanalpha light from hydrogen atoms spread throughout the solar system and interstellar space Lyman-alpha Skyglow Would look like an overcast sky Naturally shines down on the moon s PSRs Star light is another illumination source we exploit Nozomi data IUE-Based FUV Stellar Illumination 7

8 Water Ice Detection Technique Lab measured water frost reflectance shows a distinct, broad UV absorption band near 160 nm (Wagner et al. 1987) LAMP searches for this spectral signature of water ice in PSR albedo measurements 8

9 LAMP South Pole Brightness Map PSRs are darker than surrounding areas in the Far-UV 9

10 LAMP North Pole Brightness Map Still working to create albedo maps and spectra 10

11 Lunar Exosphere Distribution Argon distribution: Hodges et al., The Moon, 1975 Sodium Corona Image: Potter et al., JGR, 1998 Viewed at 51 lunar phase (N up, W right) Sodium and other constituents may be concentrated near the sub-solar point Argon and other constituents may be concentrated near the dawn terminator 11

12 LAMP Atmosphere Objectives Search for Ar, Ne, and He in atmosphere Search for H 2 in lunar atmosphere to confirm that solar wind protons are converted to molecules in surface Search for H and O signatures of subsurface water outgassing near the lunar poles Search for signatures of carbon-bearing volatiles, e.g., CO Search for ionospheric constituents, e.g., O + and C + Search for lunar horizon glow gas and/or dust emissions Search for localized outgassing near likely sites with targeted observations Search for transient volatiles associated with meteor showers, and magnetotail crossings 12

13 LRO/LAMP s View of LCROSS Impact During the impact, LRO flew from ~noon to ~midnight over the south pole Dusk LRO closest approach was offset from Centaur impact time by ~90 seconds Noon * Midnight 100 km Dawn 13 Animation by M. Mesarch, GSFC

14 LAMP/LCROSS Animation LAMP slit indicated by the green line near the limb (roll angle ~80.3º) Plume visible above limb (seen from LRO) at altitudes >35 km 8 consecutive orbits: 2 before, 1 during, and 5 after LCROSS Centaur target in Cabeus crater: lat = º lon = º UT = 11:31:19 14

15 Summary LAMP detected a response to the LCROSS impact that we tentatively identify as H 2 molecular fluorescence emission and resonantly scattered Hg I and Fe I emission Work in progress LRO/LAMP is mapping out and searching for exposed water ice in permanently shadowed regions at the poles LAMP uses a spectral finger-print for water ice that has the potential to definitively identify exposed water ice on the surface LAMP will continue to study how water and other volatiles are formed and are transported through the lunar atmosphere 21