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Extinct nuclides in and chronology of the early solar system

Extinct nuclides in and chronology of the early solar system. Can extinct nuclides be used for chronology? Were extinct nuclides distributed homogeneously in the solar system? How were extinct nuclides produced? Solar or nucleo-synthetic? Al-Mg, Fe-Ni, Ca-K, Be-B and Mn-Cr.

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Extinct nuclides in and chronology of the early solar system

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  1. Extinct nuclides in and chronology of the early solar system • Can extinct nuclides be used for chronology? • Were extinct nuclides distributed homogeneously in the solar system? • How were extinct nuclides produced? • Solar or nucleo-synthetic? • Al-Mg, Fe-Ni, Ca-K, Be-B and Mn-Cr

  2. New developments of Al-Mg systematics • Half life =0.73 Ma • Canonical value of the initial 26Al/27Al for CAIs (Ca-Al-rich Inclusion = refractory inclusion) was 5x10-5. • SIMS(high spatial resolution) • Internal isochron for chondrules • MC-ICPMS (high precision, low spatial resolution) • Bulk CAIs • Internal isochron for CAIs • Bulk chondrules

  3. Internal isochrons for CAIs, Young et al., 2005

  4. Internal isochrons for Chondrules, Kita et al., 2005

  5. Formation ages of chondrules, Kita et al., 2005 From CAI

  6. Al-Mg ages of bulk chondrules (Bizzarro et al., 2004)Ages from CAI are shown.

  7. Summary of Al-Mg • CAIs formed with initial 26Al/27Al ratios as high as 6.5x10-5. • The canonical value (5x10-5) is probably due to resetting of anorthite. (measured by SIMS) • High temperatures in CAI forming region continued ~300,000 years. • Chondrule precursors are as old as CAIs. • Chondrule formation continued ~2 Ma.

  8. Half life of 60Fe is 1.5 Ma.60Fe is not produced by solar cosmic ray.60Fe has to be injected from a nearby supernova.

  9. Fe-Ni systematics

  10. 60Fe in the early solar system Decay curve

  11. summary on 60Fe • 60Fe is produced by supernova, but not produced by solar cosmic ray. Therefore, it is very important for understanding origins of short-lived nuclides. • 60Fe seems to be present in the early solar system, but the distribution may have been heterogeneous.

  12. 41Ca • Half life of 41Ca is 0.15 Ma. • Nearly constant initial ratios of 41Ca/40Ca ~1.4x10-8are observed for CAIs with 26Al. • If 41Ca is absent, 26Al is also absent. • FUN (fractionation & unknown nuclear component) inclusions • This was explained by a late injection model. But now that CAI formation seems to have continued for 300,000 years, there seems to be a problem.

  13. 41Ca in CAIs (Sahijpal et al., 1998) FUN

  14. What you expect from a late injection model (Sahijpal & Goswami, 1998) NormalCAI FUN

  15. Late injection model:41Ca and 26Al

  16. 10Be (half life =1.5 Ma) produced by cosmic ray • Abundant 10Be in CAIs was initially considered to be produced by solar cosmic ray. • However, it was later shown that it may be GCR10Be trapped in cores of molecular clouds.(Desch, 2003) • FUN inclusions contain 10Be and do not contain 26Al. • Normal CAIs contain both 10Be and 26Al. • Solar cosmic ray scenario • Fun inclusions are evaporation residues irradiated by solar cosmic ray? • Normal CAIs are condensates getting the 10Be and 26Al from the irradiated nebula? • Galactic cosmic ray scenario • Fun inclusions are evaporation residues or condensates formed before injection of 26Al? • Normal inclusions are condensates formed after injection of 26Al?

  17. １０Be, 26Al and 41Ca in CAIs Normal inclusions 10Be/9Be Late injection FUN inclusions

  18. 53Mn-53Cr, half-life = 3.7 Ma • Suitable for studying planetary processes • Initial ratios of 53Mn/55Mn in CAIs are not well established. • Recently, comparison with Al-Mg and Pb-Pb ages became possible for eucrites and angrites. • Previously such comparison was made for chondrites but was not conclusive.

  19. High initial Mn ratios for CAIs are inconsistent with Al-Mg system and could be due to heterogeneity of the nebula or due to disturbed Mn-Cr system Papanastassiou et al., 2005

  20. Age comparisonAl-Mg, Mn-Cr and Pb-Pb agesCAI, eucrite and angrites

  21. Summary on Mn-Cr and comparison • Al-Mg and Mn-Cr systems can be used as chronometers. • Absolute ages of CAIs are probably ~4568Ma.

  22. conclusions • Can extinct nuclides be used for chronology? • Probably yes: 10Be, 26Al (excluding FUN), 53Mn (excluding CAIs) • Not sure: 41Ca, 60Fe • How were extinct nuclides produced? • Because of 60Fe, nucleo-synthetic origin seems more likely than SCR origin. • But, the late injection model need closer examination.

  23. Initial 53Mn/55Mn in CAIs (Nyquist et al., 2001)

  24. Mn-Cr age of chondrules (Nyquist et al., 2001)

  25. Al-Mg system of a CAI measured with ICPMS (Young et al., 2002) Internal isochron

  26. Al-Mg ages of CAIs (Bizzarro et al., 2004) MC-ICP-MS of bulk CAIs The initial 26Al/27Al ratio is 6.0x10-5 if equilibrium fractionation law is used.

  27. Angrite (S99555)

  28. Eucrite (Juvinus) with impact melt

  29. Solar nebula before exposed to supernova ejecta. Hester et al., 2004

  30. Tachibana et al., 2005

  31. Angrite (error bars are one sigma.)

  32. More on 10Be • So far, internal isochron for the first 1~3 Ma is made only with Al-Mg system.Thus, cannot be cross-calibrated. • e.g.dating of chondrules. • Mn-Cr cannot be used because the initial in CAIs are strange. • 10Be seems to be hopeful.

  33. 10Be in FUN

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