12-14 May, 2008 SERENA, Santa Fe, NM 1

Mid-IR observations of Mercury’s Surface as related to

MERTIS and PEL and BED

(and SERENA, of course)

12-14 May, 2008 SERENA, Santa Fe, NM 2

Ann L. SpragueLunar and Planetary Laboratory, Tucson, AZ, USA

With many collaborators over 2 decades:

Surface studies: GROUND-BASED--Kozlowski, Donaldson Hanna, Warell, Helbert, Maturilli, Russel, Lynch, Witteborn, Lebofsky,

Wooden, Hora, Kasis, Cruikshank, Graps, Deutch

MESSENGER--MASCS, GRNS, XRS: Domingue, Vilas, McClintock, Izenberg, Holsclaw, Blewett, Head, Helbert,

McCoy, Murchie, Goldsten, Lawrence, Boynton, Feldman, Evans, Nittler, Schlemm, Rhodes, Starr, Robinson,

Solomon and the MESSENGER TEAM

12-14 May, 2008 SERENA, Santa Fe, NM 3

Ground-based and MESSENGER VIS NIR spectroscopy

demonstrated no or very little FeO in Mercury’s regolith

Ground-based summary: Vilas et al. (1994)

A couple of detections of shallow Fe-bearing clinopyroxene at both N and S at high

latitudes, 170º to 230º E Warell et al. (2006)

MESSENGER MASCS McClintock et al. Submitted to Science,

2008

12-14 May, 2008 SERENA, Santa Fe, NM 4

What might we see with the neutral and ionised particle analyser

SERENA (IFSI Italy) coming directly from Mercury’s surface?

12-14 May, 2008 SERENA, Santa Fe, NM 5

a. 55N, 27S; b. 6E, 354W radar spots

B and Ab. Samec. Same, also

Kuiper-Murasaki craters

d. Spots B and Ae. Samef. Sameg. Caloris Basin h. 65N, 155W

0, 125W 9S, 105Wi. 35S, 43-73W

Sprague et al. 1998

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atmosphericK

emissionsurfacereflectionin bandcontinuum

Adapted from Potter and Morgan PSS (1997)

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The Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS)

H. Hiesinger, J. Helbert and the MERTIS Co-I Team

12-14 May, 2008 SERENA, Santa Fe, NM 8

Plagioclase in some detail

Data from PEL, Berlin Emissivity Database, (Helbert et al. 2006)

12-14 May, 2008 SERENA, Santa Fe, NM 9

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

New: There are compositiondifferences betweenCaloris Basin,dark plainsmaterial, and radar bright region “C”

12-14 May, 2008 SERENA, Santa Fe, NM 10

MDIS image of region measured in mid-infrared spectral imaging discussed in this paper. This region, also known as radar bright region "C" also has a prominent impact crater centered at 114°E, 11° N and its system of ejecta rays appearing brighter against the darker heavily cratered surface beneath.

12-14 May, 2008 SERENA, Santa Fe, NM 11

(left) Goldstone-VLA X-band imaging showing radar-bright region "C" as the dark irregular patch--adapted from Butler et al. (1993). (right) Aricebo S-band dual polarization, delay-Doppler imaging showing same region as heavily cratered. Only the regions north of the "ambiguity line" approximately at the equator are relevant-- reproduced from Harmon et al. (2007).

210º to 270º W Longitude

12-14 May, 2008 SERENA, Santa Fe, NM 12

Key to Mineral types on following slides

• Pyroxenes– (e) enstatite: Mg-rich (h) hypersthene: Mg,Fe– (diop) diopside: Ca,Mg (hed) hedenbergite Fe,Ca

• Plagioclase Na-rich ~90 down to 30 wgt% Na– (and) andesine Na (olig) oligiclase Na – (lab) labradorite Na,Ca (byt) bytownite Ca,Na

• Olivine– Mg-rich variety ~70 to 97 wgt% >>>FO(70),

FO(97)• Garnet

– (p) pyrope Mg - variety– (g) grossular Ca-variety

12-14 May, 2008 SERENA, Santa Fe, NM 13

bright region "C" data--black

models --grey wide range of grain sizes 5 options for comparison 4 different opaque phases

a) 90 spectral end members

180 spectral end membersb) rutile (TiO2) permitted, rutile chosenc) ilmenite permitted (FeTiO3),

but ilmenite not chosend) perovskite (CaTiO3) permitted, perovskite chosene) troilite (FeS) permitted,

troilite chosen

12-14 May, 2008 SERENA, Santa Fe, NM 14

Enstatite.1(Salisbury et al., 1988)SiO2 56.70TiO2 0.01Al2O3 1.69Fe2O3 2.18FeO 4.79MnO 0.15MgO 35.25CaO 0.85Na2O 0.02K2O 0.02

Total 99.66

Hypersthene.1F(Salisbury et al.,

1987)SiO2 51.32Al2O3 4.89FeO 17.07MgO 26.09CaO 1.27K2O 0.02Na2O 0.05TiO2 0.29MnO 0.35

Total 101.33

orthopyroxene

12-14 May, 2008 SERENA, Santa Fe, NM 15

Labradorite.1F(Salisbury et al., 1987)

SiO2 51.42TiO2 0.04Al2O3 30.76Fe2O3 0.24FeO 0.17MnO not reportedMgO 0.05CaO 13.42Na2O 3.52K2O 0.23H2O 0.04Total 99.89

Albite.1F(Salisbury et al., 1987)SiO2 68.18Al2O3 20.07FeO 0.01MgO 0.02CaO 0.02K2O 0.20Na2O 10.37TiO2 0.01MnO 0.01

Total 99.88

plagioclase feldspar

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  Radar Bright C region resultsMineral

TypeLimited# end

members

RutileTiO2

IlmeniteFeTiO3

Perovskite

CaTiO3

TroiliteFeS

Ortho-pyroxene

54 (e) 33 (e) (h) 17 (e) 14 (e) (h) 45 (e) (h)

Clino-pyroxene

0 0 37 (hed)

20 (d) 0

olivine 5 Fo(91) 5 Fo(66) 0 25 Fo (88) 6 Fo(79)plagioclase

9 (lab) 14 (lab) 14 (lab) 0 0

orthoclase

24 35 26 18 21

garnet 5 (p)2 (g)

0.7 (p)0.9 (g)

3 (p)0 (g)

0 2 (p)0 (g)

opaque 0 yes 0 yes yes

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• Color and albedo controlled by maturity and composition

• Map units statistically, next step is determine origin

• PC 2 interpreted to represent compositional variation

Caloris Basin smooth plains

Lowalbedo material

Smooth plainsLow albedo

PC 2

MNF (minimum noise fraction,similar to PC) 2-1-3 as R-G-B

Lowalbedomaterial“streak”

From Robinson et al. LPSC 2008

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Next sequences from Donaldson Hanna et al 2008EGU, Vienna, Austria

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Caloris Basin Observations8 April 2006 - 0080

9 April 2006 - 0070

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Best Fit Models – Caloris Basin

9 April 2006

8 April 2006

EM

EM TM

TM

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Sanidine.3 (K,Na)Al3O8

Salisbury et al. (1991)SiO2 67.43Al2O3 18.65FeO 0.59MgO 0.03CaO 0.02K2O 7.38Na2O 5.38TiO2 0.03MnO 0.02Total 99.97

Orthoclase.3 KAlSi3O8Salisbury et al. (1991)

SiO2 64.81TiO2 0.02Al2O3 19.11MnO 0.03K2O 13.51Na2O 1.69FeO 0.02MgO 0.04CaO 0.04Total 99.34

Potassium feldspars: K-spars

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Caloris Basin Results

Merc0080 Merc0070Minerals 2006-04-08 2006-04-09K - Feldspar 20% [sanidine] 28% [sanidine]Plagioclase 15% [labradorite] 12% [labradorite]Orthopyroxene 7% [enstatite]

5% [hypersthene]10% [hypersthene]

Clinopyroxene 19% [augite] 27% [augite]Olivine <3% [forsterite] <1% [forsterite]MISSING MATERIAL WHAT??

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Dark Plains Observations8 April 2006 - 0098

9 April 2006 - 0063

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Best Fit Models – Dark Plains

8 April 2006

9 April 2006

TM

TM

EM

EM

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Dark Plains ResultsMerc0098 Merc0063

Minerals 2006-04-08 2006-04-09Plagioclase 27% [labradorite] 31% [labradorite]

Orthopyroxene 11% [hypersthene] 6% [hypersthene]

Clinopyroxene 22% [augite] 36% [augite]Olivine 6% [forsterite] 2% [forsterite]MISSING MATERIAL WHAT??

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Rutile TiO2

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Perovskite CaTiO3

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Ilmenite FeTiO3

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Meteoritic troilite FeS

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Observation

Location:all E

longitude

Reported Result

1)Sprague et al. (1994)

338° to 348°250°

alkali basaltlabradorite

2)Sprague et al. (1997)

240° to 250° 330° E

labradorite, 52-61 wgt. %SiO2; 90% feldspar & 10% Mg-pyroxene

3)Emery et al. (1998)

295° to 350°200° to 260°

not modelednepheline alkali syenite

4)Sprague et al. (1998)

240° to 250° 90% labradorite & 10% enstatite

5)Cooper et al. (2001)

20° S to 20° N275° ±10°180° ±10°,170° ±10°,350° ±10° 215° ± 10°

~ 44 wgt% SiO245-57 wgt% SiO2 ~50 and ~42 wgt. % SiO2

12-14 May, 2008 SERENA, Santa Fe, NM 31

6)Sprague et al. (2002)

20° S to 20° N275° to 315° 252° to 292°

52-61 wgt. %SiO2; labradorite and clinopyroxenepyroxene (unspecified)

7)Warell et al. (2006)

50° to 75° N, 110° 50° to 75° S, 166° to 250°50° to 75° N, 166° to 250°

no FeOorthopyroxene 52 - 61 wgt.%SiO2clinopyroxene 52 - 61 wgt.%SiO2

8)Sprague et al. (2008) EGU

0° to 30° N100° to 140°

enstatite, forsterite, orthoclaselabradorite,Mg-garnet, rutile?/perovskite?

9) Donaldson Hanna et al. (2008) EGU

Caloris Basin

Dark Surrounding Plains

K-spar, plagioclase, clinopyroxene,orthopyroxene

12-14 May, 2008 SERENA, Santa Fe, NM 32

Challenges for SERENA●Quantify neutral and ions sputtered

Mg, Al, Ca, O, etc. from pyroxenes and feldspars

●Quantify Na, K, and if possible locate it● Distinguish between solar Fe and Fe

from surface materials—is it possible?● Perhaps use knowledge of H, H2 and

He as a “boot strap” to distinguishing between solar wind and surface mineral partitioning??

12-14 May, 2008 SERENA, Santa Fe, NM 33

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