Compositional Relationships With the Surface and CrustThe exosphere and related SERENA particle experiments

Ann L. SpragueLunar and Planetary Laboratory, Tucson, AZ, USAWith many, many collaborators over 2 decades:

Exosphere studies-groundbased: Hunten, Hill, Kozlowski, Grosse, Wells, Domingue, Fink, Schneider, Killen, Potter, Morgan, Mendillo, Wilson, Baumgardner

Exosphere studies-MESSENGER: MASCS--McClintock, Bradley, Vervak, Killen, Izenberg, Holsclaw, Kochte, Lankton, Mouawad FIPS--Raines, Gloeckler, Kabin, Krimigis, Andrews, Slavin, KoehnAnd the MESSENGER AMDG TEAM

What might we see with the neutral and ionised particle analyser SERENA (IFSI Italy) ?FIPS am I allowed to say WOW! exceeds expectations?Ions sputtered from surface and ionized from neutrals in atmosphereNeutrals in atmosphereSolar Wind ionsmaterial delivered to surface which is implanted into surface

Pickup Ion CompositionFrom Zurbuchen et al. 2008, EGU, Vienna, Austria

Geopotential Scale Heights (km)assumed temperature 1000 K

Height(Mer R)g(cm/sec2)HNaSKCaFe1.0372223697705756371.51655030219157129126842.09389433892792292241492.560139736084373583492333.041201228756295165033353.5302738811918567026854564.02335772155511189178945964.518452741968141511611132755

Near-surfacemeasurementsof Na and K

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

MDIS ColorThree major unitsSmooth plainsAverage crustal materialLow albedo / relatively blue crustal material

Minor unitsDiffuse red material

High albedo / relatively blue crater floor and ray material

High albedo materials on crater floors and central peaksAdapted From Head et al. LPSC 2008

Atmospheric potassium, K(ionization time Na/K = 1.5 at 0.31 AU). Observations show it close to the surface. MASCS will determine if there is an extended componentor maybe Rosemarys and Drews work. K emissionSurfaceReflectionin bandcontinuumAdapted from Potter and Morgan PSS (1997)

55N, 27S; 6E, 354W radar spots B and Ab. Samec. Same, also Kuiper-Murasaki cratersd. Spots B and Ae. Samef. Sameg. Caloris Basin h. 65N, 155W 0, 125W 9S, 105Wi. 35S, 43-73W Sprague et al. 1998

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington lookingnorth

Imaging the sources and full extent ofthe sodium tailof the planetMercury

Baumgardner,Wilson, Mendillo,GRL, 35, 2008

3.7m AEOS telescope on Maui, June 8, 2006Baumgardner et al. 2008~88 W long sub-earthnot radarA and BNa+ implantand subsequentrelease?Or.reallyNa-rich polar regions??

Ion ImplantationSubsequent release to exosphereHigh energy processPhoto sputteringCharged particle sputteringHigh energy comaLow energy processThermal desorptionDiurnal effect

Impact distribution of Ca+11 on the surface of Mercury for specific solar wind conditions. Southern hemisphere impact sites dominate. Color bar--the number of parcels impacting per site. Each parcel represents ~1017 Ca ions. Similar behavior, with more pronounced preference for southern hemisphere impacts is seen for O+6. (Patrick Koehn, 2006)

Observations of CaHigh Resolution SpectrographKeck IMauna Kea HawaiiBida et al. 2000

Killen et al. 2004Radiance of emission~ 2.5 k RayHigh radial velocity (-2 km/s)indicates high energy

Strong Diurnal Effect Morning High/Afternoon LowNaK

Adapted from Raymond et al. 1997

Challenges for SERENASort out the true surface components from the solar implanted componentsDetermine the fractional amount of recycling per pristine surface atomObserve impacts and measure exogenous components from first sightDiscover new species and secular variation eg. impacts, ecliptic variation, comet trails, other dust regions

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