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Ages of Dated Martian Events. Salts shergottites (0-175 Ma). Iddingsite nakhlites (633 ± 23 Ma). Carbonates ALH84001 (3929 ± 37 Ma). Shergotty (165 ± 11 Ma). Zagami (169 ± 7 Ma). LA1 (170 ± 7 Ma). NWA856 (170 ± 19 Ma). 174 ± 2 Ma. EET79001A (173 ± 10 Ma).
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Ages of Dated Martian Events Salts shergottites (0-175 Ma) Iddingsite nakhlites (633 ± 23 Ma) Carbonates ALH84001 (3929 ± 37 Ma) Shergotty (165 ± 11 Ma) Zagami (169 ± 7 Ma) LA1 (170 ± 7 Ma) NWA856 (170 ± 19 Ma) 174 ± 2 Ma EET79001A (173 ± 10 Ma) Y793605 (173 ± 14 Ma) EET79001B (173 ± 3 Ma) ALH77005 (177 ± 6 Ma) LEW88516 (178 ± 9 Ma) NWA1056 (185 ± 11 Ma) Y980459 (290 ± 40 Ma) 332 ± 9 Ma QUE94201 (327 ± 10 Ma) NWA1195 (348 ± 19 Ma) DaG 476 (474 ± 11 Ma) Dhofar 019 (575 ± 7 Ma) Nakhla (1260 ± 70 Ma) NWA998 (1290 ± 50 Ma) 1327 ± 39 Ma Y000593 (1310 ± 30 Ma) Lafayette (1320 ± 50 Ma) Chassigny (1362 ± 62) Gov. Valad. (1370 ± 20 Ma) ALH84001 (4500 ± 130 Ma) Silicate differentiation (4526 ± 21 Ma) Core segregation (4556 ± 1 Ma) LEW86010; silicate differentiation reference (4558 ± 0.5 Ma) CAI (solar system formation reference) (4567 ± 0.6 Ma) 0 1000 2000 3000 4000 4657 Age (Ma) Borg & Drake Figure 1
Two-Stage Nd Isotope Evolution Model +21 4.526 Ga -19 4.3 Ga 4.4 Ga 4.0 Ga 4.2 Ga 4.5 Ga 4.558 Ga 60 0.300 QUE 40 DaG 0.250 20 Initial eNd143 at 175 Ma EET B EET A ALH 0.1967 (CHUR) 0 Zagami Shergotty -20 0.150 -0.5 0 0.5 1 1.5 Present-day eNd142 Borg & Drake Figure 2
0.726 0.724 0.722 0.720 0.718 0.716 0.714 0.712 0.710 Age – ISr for youngest Shergottites 42 Ma 4 Ma Shergotty NWA1068 Zagami NWA856 LA1 DTimeRate of Magmatism 4 Ma 0.4 Ma/event 42 Ma 4.2 Ma/event Initial 87Sr/86Sr ratio EET79001B EET79001A LEW88516 Y793605 ALH77005 150 160 170 180 190 200 Age (Ma) Borg & Drake Figure 3
ALH84001 Carbonate Formation Ages 0.85 T = 3924 ± 19 Ma S6 ISr = 0.70199 ± 7 S7 0.80 S8 87Sr/86Sr 200 0.75 +19 100 S1 εSr S2 0 S5 -19 S3 0.70 S4 -100 1 0 2 3 0 1 2 3 87Rb/86Sr S7 T = 4045 ± 90 Ga 25 S4 20 S5 S3 207Pb/204Pb S6 S8 S2 15 S1 10 10 20 30 40 206Pb/204Pb Borg & Drake Figure 4
Rb-Sr ages Y000593 (Shih et al., 2002) Rb-Sr age Lafayette (Shih et al., 1998) K-Ar ages Lafayette (Swindle et al., 2000) Thermal metamorphism (K-Ar ages) x = 633 ± 23 Ma Ages of Iddingsite from the Nakhlites 614 ± 29 Ma 650 ± 80 Ma 679 ± 66 Ma 670 ± 91 Ma 0 200 400 600 800 Age (Ma) Borg & Drake Figure 5
Atmosphere Xe I- Water 129Xe 129I Borg & Drake Figure 6 Mars Outgassing Model