Martian Geochronology from Meteorites and Crater Counts L. E. Nyquist KR NASA Johnson Space Center, Houston, TX, USA Acknowledgments: C.-Y. Shih, D. Bogard, J. Park Introduction and Overview ? Current status of Martian meteorite (MM) ages ? Methods, examples, and factors ? No “old” shergottites ? Comparisons to cratering chronologies ? Hartmann/Neukum ?S. Werner’s 2005 Ph. D. thesis ? Stöffler-Ryder derived curve ?Implications for meteorite source regions ? Possibilities for calibrating the cratering curve ? Possibilities for dating secondary mineralization ? Example: Nakhlite iddingsite. ?VERY preliminary Rb-Sr studies of sulfates ? Some analytical requirements for in situ age dating ? Mostly for Rb-Sr, Sm-Nd Martian and Lunar Meteorite Ages and Cratering Chronology 2 MN FH boundaries 101 EN LN EH LH EA MA LA Lunar Meteorites Period 100 Neukum et al. (2001) Moon Martian Meteorites -1 Lunar data EN ~1% ) 10 (Stoeffler & Ryder, 2001) -2 Mars = 1.55 x Lunar data MN/LN 10-2 Autolycus Aristillus ~19% Werner (2005) H~21% Mars N(1) (km 10-3 EA ~9% MA ~5% 10-4 AAa2n ~AEC2 Werner (2005) LA ~2% 10-5 5 4 3 2 1 0 % Surface Time before Present (Ga) Area Cerberus Plains S Zunil Crater AEC2 AAa2n Elysium Mons Olympus Mons AAa1n Werner (2005), Fig. 14.3. Geologic map from Tanaka et al. (2005) with numbered units for crater size-frequency distribution measurements by Werner. Adapted from S. Werner (Thesis, 2005) Adapted from Ph. D. Thesis of S. Werner (2005; Fig. 15.13) From S. Werner (Thesis, 2005, Fig. 14.11) Radiometric Lunar and Martian Surface Ages and Impact Chronology 5 4 3 2 1 0 101 Ka 009A881757 Dho287A 100 LAP02205NWA 032Lunar Meteorites Y86032 Neukum et al. (2001) Moon Martian Meteorites -1 Lunar data EN ~1% ) 10 (Stoeffler & Ryder, 2001) -2 Mars = 1.55 x Lunar data MN/LN 10-2 Autolycus Aristillus ~19% Werner (2005) H~21% Mars N(1) (km 10-3 EA ~9% MA ~5% Hartmann (2005): -4 AAa2n 10 ? log N = +0.1911 shallow, M ~AEC2 LA ~2% (NM/Nm)T, 2<D<50 = 1.55 Werner (2005) 10-5 5 4 3 2 1 0 % Surface Time before Present (Ga) Area Impact Chronology of Mars Nyquist (2005) : Revised Martian Crater Curve 30 (= Stoeffler & Ryder (2001) Lunar x 1.55) 25 Martian Meteorites (solid symbols) NDDS melts unsampled 20 A Hesperian 15 LN/MN 10 Surface Area (Vol. %) 5 EN 0 4 3 2 1 0 Time before Present (Ga) Percentage of Exposed Volcanics on Modern Mars in Each Epoch 30 Noachian Hesperian Amazonian 25 20 Hartmann/Ivanov 15 Neukum/Ivanov 10 Surface Area % 5 H A N 0 4 3 2 1 0 Time before Present (Ga) NWA 1460 Basaltic Shergottite Basaltic Shergottite - NWA 1460 0.714 interior fines Px2(r) 0.713 Px2a(r) T=336±15 Ma Px1(r) I(Sr)=0.708968±30 Pxf(r) 0.712 Sr 87 86 86 Opq(r) Rb/ Sr 0.711 Leach 0.0 0.2 0.4 0.6 0.8 1.0 Sr/ WR2(l) 87 1 +15 Ma 0.710 0 ?Sr WR2(r) -1 WR2 -2 -15 Ma 0.709 Plag1,2(r) 0.0 0.2 0.4 0.6 0.8 1.0 87Rb/86Sr Basaltic Shergottite - NWA 1460 0.5134 interior fines Px2a(r) 0.5132 Px1(r) T=350±16 Ma WR(r) ? =+10.6±0.5 Px2(r) 0.5130 Nd Opq(r) Nd 144 147Sm/144Nd 0.5128 0.2 0.4 0.6 Nd/ WR2 143 Leach 0.8 0.5126 WR2(l) 0.4 -16Ma 0.0 ?Nd Plag2(r) -0.4 +16Ma -0.8 0.5124 Plag(r) 0.2 0.3 0.4 0.5 0.6 147Sm/144Nd Basaltic Shergottite - NWA 1460 16000 NWA 1460 - Plag 6-98% 39Ar 12000 -Trap Ar Age = 353±16 Ma 36 40 36 8000 ( Ar/ Ar)Tr=372±98 Ar/ 36 37 40 Ar/ Ar=0.000589 4000 Age = 334±19 Ma 40 36 ( Ar/ Ar)Tr=434±97 36Ar/37Ar=0.000456 0 0 400 800 1200 1600 39 36 Ar/ Ar-Trap 4000 Isochron Age Zagami FG-Plag 3500 = ?300 Myr 3000 40Arxs is distributed through the lattice 2500 Ar 36 2000 Ar / Larger 40Arxs (at 40 1500 intermediate temp 0-25% 1000 extractions 23-54% 54-98.5% of 39Ar ) 500 25-54% “hump” : 0 0 50 100 150 200 250 300 350 40Ar/36Ar= ?1000 39Ar / 36Ar (could be Martian atm in a shock Bogard & Park (2008) produced phase) Slide courtesy of J. Park Excess 40Ar in Zagami Mineral Separates Phase 40Ar % total Values calculated by xs subtracting from -7 3 CG-Plag 15.7x 10 cm 32 measured 40Ar, the FG-Plag* 23.4 (17.9)x 10-7 cm3 54 amount of 40Ar* in situ, CG-Px2 10.8x 10-7 cm 3 85 assuming Zagami formation age of 170 Myr. FG-Px 2 9.2x 10-7 cm 3 86 FG-Px 1 15.3x 10-7 cm 3 89 No significant difference between CG & FG, nor between Plag & Pyx (*Second value for FG-Plag subtracts the trapped component with 40Ar/36Ar=1000.) 40Ar = ?1-2x10-6 Bogard & Park (2008) suggest xs (in cm3STP/g) Similar 40Ar excesses are also observed in other shergottites (Bogard, Park & Garrison, 2008, submitted. Courtesy of J. Park) For Nakhlites: Common Age; No Evidence of Significant Excess 40Ar 20000 Isochron Age =1325 ±18 Myr Nakhlites 18000 R2=0.9986 MIL03346 16000 NWA-998 14000 Y-000593 12000 Nakhla Gov. Valadares 10000 Lafayette 2400 K ppm 8000 Chassigny 6000 4000 2000 0 0 0.0E+00 2.0E-05 4.0E-05 6.0E-05 8.0E-05 1.0E-04 1.2E-04 1.4E-04 1.6E-04 40 3 Total Ar cm /g Courtesy D. Bogard Common Age and 10-22 x10-7 cm3/g Magma-Derived 40Ar 5000 Shergottites Zagami All 170 Myr Los Angeles Isochrons 4000 NWA3171 Shergotty 3000 NWA2975, 1068 Y-00097, 793605 [ K ] ppm EET79001 2000 glass 1000 High-K Plag Low-K Pyx Mid-K WR 0 0 10 20 30 40 50 60 70 80 Total 40Ar, 10-7 cm3/g Courtesy of D. Bogard Basaltic & Lherzolitic Shergottites 1.0 ? =5 ?=6 ? =4 ?=8 Zagami T=700 Ma ?=6 Chen & Wasserburg (1986) Bouvier et al. (2005) Pb Borg et al. (2005) 206 0.9 ?=8 Shergotty T=173 Ma Chen & Wasserburg (1986) Pb/ ? =10 Sano et al. (2000) wtd avg. 207 Los Angeles Sh Phos Blanks Bouvier et al. (2005) (SIMS) EETA 79001 EETA LA MT Chen & Wasserburg (1986) Y793605 Sh,Za Misawa et al. (1997) Y79 0.8 0.05 0.06 0.07 0.08 0.09 4.0 Ga 173 Ma 204Pb/206Pb Shergottites LA Zagami Mask. leach Zagami (Bouvier et al. 2005) 1.0 Shergotty i MT 0.8 Pb) 206 95% conf. intervals Pb/ 0.6 Assimilant range 207 ( 0.4 "4.0" Ga line 0.00 0.02 0.04 0.06 0.08 204 206 ( Pb/ Pb)i Shergottites 0.08 Zagami LA Chen & Wasserbug ; Borg et al i 0.07 Shergotty Bouvier et al Pb) 95% conf. intervals 206 ~0.064 0.06 Pb/ Assimilant range 204 ( 0.05 ~0.725 Assimilant range 0.720 0.722 0.724 0.726 0.728 0.730 87 86 ( Sr/ Sr)i ~0.3 Ga ~2.6 Ga ~1.6 Ga Spirit Opportunity Figure 1 from Nimmo and Tanaka (2005) Ann. Rev. Earth Planet. Sci., 33, 133-161 Surface ages from Hartmann et al. (1981) Young Elysium Volcanics ~100 Ma Apollinaris Patera 3.7 to ~3.1 Ga 10 S Gusev X Spirit 15 S ~3.6 to ~1.8 Ga >3.7 Ga 170 E 175 E 180 E Gusev Crater with Apollinaris Patera Image and Age Ranges Courtesy of K. Tanaka Nakhlite - MIL 03346 0.5128 T=1.36±0.03 Ga Cpx2(r) WR1,2(r) ?Nd=+15.2±0.2 Cpx1 0.5124 Cpx3 Nd 147 144 144 WR1 Sm/ Nd 0.12 0.16 0.20 Nd/ Gl Ol2 143 0.4 +30Ma 0.5120 Ol 0.0 ?Nd WR(l) Cpx2(l) -0.4 -30Ma 0.5116 0.09 0.11 0.13 0.15 0.17 0.19 0.21 147Sm/144Nd Nakhlite - Lafayette 0.708 T=1.26+0.07 Ga ISr=0.70260+0.00014 WR(l) 0.706 Ol(r) Id1(l) Id2(l) Sr Id2(r) 86 WR2 Px(l) Sr/ WR1 Ol(l) 87 WR(r) Id1(r) 0.704 Px(r) Tidd?=~680 Ma 0.702 0.0 0.1 0.2 0.3 87Rb/86Sr Shih et al. (1998) Kuebler et al. (2003) A study of olivine alteration to iddingsite using Raman spectroscopy. LPSC34. “Iddingsite...a catch-all term to describe reddish alteration products of olivine...an Å-scale intergrowth of goethite and smectite (saponite)... “Alteration conserves Fe (albeit oxidized), but requires addition of Al and H2O and removal of Mg and Si.” Kuebler et al. (2003), Fig. 2. Orthopyroxenite ALH84001 0.85 Silicates S6 T = 4.55+0.30 Ga ISr = 0.6997+0.0020 0.80 Sr 86 Sr/ 87 Carbonates 0.75 T = 3.90+0.04 Ga ISr = 0.70205+0.00013 S5 0.70 S4 0.0 0.5 1.0 1.5 2.0 2.5 3.0 87Rb/86Sr Borg et al. (1999) The age of the carbonates in Martian Meteorite ALH84001. Science, 286, 90-94. Clark et al. (2005) Chemistry and mineralogy of outcrops at Meridiani Planum. EPSL 240, 73-94. Fig. 12 showing the modeled mineral components of outcrops at Endurance, Fram, and Eagle Craters from the APXS and MB instruments.