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Lithium nucleosynthesis in the Sun inferred from the solar-wind 7Li/6Li ratio


The abundance of lithium measured in meteorites has generally been assumed to be the ‘Solar System value’, which presumably reflects the abundance in the gas cloud out of which the Sun formed1. Lithium is a factor of 140 less abundant in the solar photosphere than in meteorites2; this difference has been attributed to the destruction of lithium (through nuclear reactions) at the base of the Sun's convection zone3,4,5. If this is correct, then the ratio of 7Li/6Li in the Sun's photosphere should be 106 (ref. 6), as 6Li is destroyed much more easily (at a lower temperature) than 7Li: the meteoritic abundance ratio is 7Li/6Li = 12.14 (ref. 7). Here we report that 7Li/6Li = 31 ± 4 for lithium in the solar wind that has been implanted in lunar soil. This low ratio suggests that lithium is produced when energetic protons from solar flares induce spallation reactions with 16O and 12C present in the photosphere.

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Figure 1: The 7Li/6Li isotopic ratio as a function of depth for three lunar soils (labelled by sample number).
Figure 2: The 7Li/6Li isotopic ratio as a function of the atomic Si/Li ratio in lunar soils 10060 and 79035.
Figure 3: Evolution in the Sun of the 7Li/6Li ratio versus the Li/H ratio.


  1. 1

    Reeves,H. in Origin and Evolution of the Elements (eds Prantzos, N., Vangioni-Flam, E. & Cassé, M.) 168–197 (Cambridge Univ. Press, 1993).

    Google Scholar 

  2. 2

    Anders,E. & Grevesse,N. Abundances of the elements: meteoritic and Solar. Geochim. Cosmochim. Acta 53, 197–214 (1989).

    ADS  CAS  Article  Google Scholar 

  3. 3

    Herbig,G. H. Lithium abundances in F5-G8 dwarfs. Astrophys. J. 141, 588–609 (1965).

    ADS  CAS  Article  Google Scholar 

  4. 4

    Vauclair,S., Vauclair,G. Schatzman,E. & Michaud,G. Hydrodynamical instabilities in the envelopes of main-sequence stars: constraints implied by the lithium, beryllium and boron observations. Astrophys. J. 223, 567–582 (1978).

    ADS  CAS  Article  Google Scholar 

  5. 5

    Brun,A. S. & Turck-Chièze,S. in LiBeB, Cosmic Rays, and Related X- and Gamma Rays (eds Ramaty, R., Vangioni-Flam, E., Cassé, M. & Olive, K.) 64–72 (ASP Conf. Ser., Vol. 171, Astronomical Society of the Pacific, San Francisco, 1999).

    Google Scholar 

  6. 6

    Delbourgo-Salvador,P., Malinie,G. & Audouze,J. in Isotopic Ratios in the Solar System 267–272 (Toulouse Cepadues-Editions, 1984).

    Google Scholar 

  7. 7

    Chaussidon,M. & Robert,F. 7Li/6Li and 11B/10B variations in chondrules from the Semarkona unequilibrated chondrite. Earth Planet. Sci. Lett. 164, 577–589 (1998).

    ADS  CAS  Article  Google Scholar 

  8. 8

    Borg,J., Dran,J. C., Durrieu,L., Jouret,C. & Maurette,M. High voltage electron microscope studies of fossil nuclear particle tracks in extraterrestrial matter. Earth Planet. Sci. Lett. 8, 379–386 (1970).

    ADS  Article  Google Scholar 

  9. 9

    Geiss,J. Solar wind composition and implications about the history of the Solar system. Proc. 13th Int. Cosmic Ray Conf. Vol. 5, 3375–3398 (Univ. of Denver, 1973).

    Google Scholar 

  10. 10

    Becker,R. H. & Clayton,R. N. Nitrogen abundances and isotopic compositions in lunar samples. Proc. Lunar Planet Sci. Conf. 6, 2131–2149 (1975).

    ADS  CAS  Google Scholar 

  11. 11

    Deliyannis,C. P., Demarque,P. & Kawaler,S. D. Lithium in halo stars from standard evolution. Astrophys. J. Suppl. 73, 21–65 (1990).

    ADS  CAS  Article  Google Scholar 

  12. 12

    Eugster,O. & Bernas,R. Li, B, Mg and Ti isotopic abundances and search for trapped Solar wind Li in Apollo 11 and 12 material. Proc. Lunar Planet Sci. Conf. 2, 1461–1469 (1971).

    ADS  Google Scholar 

  13. 13

    Ritzenhoff,S., Schröter,E. H. & Schmidt,W. The lithium abundance in sunspots. Astron. Astrophys. 328, 695–701 (1997).

    ADS  CAS  Google Scholar 

  14. 14

    Bibring,J. P. et al. Ultrathin amorphous coatings on lunar dust grains. Science 175, 753–755 (1972).

    ADS  CAS  Article  Google Scholar 

  15. 15

    Keller,L. P. & McKay,D. S. The nature and origin of rims on lunar soil grains. Geochim. Cosmochim. Acta 61, 2331–2341 (1997).

    ADS  CAS  Article  Google Scholar 

  16. 16

    Borg,J. et al. A Monte Carlo model for the exposure history of lunar dust grains in the ancient Solar wind. Earth Planet. Sci. Lett 29, 161–174 (1976).

    ADS  Article  Google Scholar 

  17. 17

    Reedy,R. O. in The Ancient Sun (eds Pepin, R. O., Eddy, J. A. & Merril, R. B.) 365–386 (GCA Suppl. Vol. 13, Lunar and Planetary Institute, Houston, Texas) (Pergamon, 1979).

    Google Scholar 

  18. 18

    Christensen-Dalsgaard,J., Gough,D. O. & Thompson,M. J. The depth of the Solar convection zone. Astrophys. J. 378, 413–437 (1991).

    ADS  Article  Google Scholar 

  19. 19

    Audouze,J., Boulade,O., Malinie,G. & Poilane,Y. Galactic evolution of the lithium isotopes. Astron. Astrophys. 127, 164–168 (1983).

    ADS  CAS  Google Scholar 

  20. 20

    Balachandran,S. C. & Bell,R. A. Shallow mixing in the solar photosphere inferred from revised beryllium abundances. Nature 392, 791–793 (1998).

    ADS  CAS  Article  Google Scholar 

  21. 21

    Chaussidon,M. & Robert,F. Nucleosynthesis of 11B-rich boron in the pre-solar cloud recorded in meteoritic chondrules. Nature 374, 337–339 (1995).

    ADS  CAS  Article  Google Scholar 

  22. 22

    Smith,V. V., Lambert,D. L. & Nissen,P. E. The 7Li/6Li ratio in the metal-poor halo dwarfs HD 19445 and HD 84937. Astrophys. J. 408, 262–276 (1993).

    ADS  CAS  Article  Google Scholar 

  23. 23

    Nishiizumi,K., Caffee,M. W. & Arnold,J. R. 10Be from the active Sun. Proc. Lunar Planet. Sci. Conf. 28, 1027–1028 (1997).

    ADS  Google Scholar 

  24. 24

    Jull,A. J. T., Lal,D. & Donahue,D. J. Evidence for a non-cosmogenic implanted 14C component in lunar samples. Earth Planet. Sci. Lett. 136, 693–702 (1995).

    ADS  CAS  Article  Google Scholar 

  25. 25

    Sisterson,J. M., Kim,K., Caffee,M. W. & Reedy,R. C. 10Be and 26Al production in lunar rock 68815: revised production rates using new cross section measurements. Proc. Lunar Planet. Sci. Conf. 28, 1327–1328 (1997).

    ADS  Google Scholar 

  26. 26

    Reeves,H. On the origin of the light elements. Annu. Rev. Astron. Astrophys. 12, 437–467 (1974).

    ADS  Article  Google Scholar 

  27. 27

    Hashizume,K., Marty,B. & Wieler,R. Single grain analyses of the nitrogen isotopic composition in the lunar regolith: in search of the Solar wind component. Proc. Lunar Planet. Sci. Conf. 30, 1567–1568 (1999).

    ADS  Google Scholar 

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We thank J. Audouze, S. Vauclair and R. Reedy for discussions, and G. Huss for contributions to this Letter. This work was supported by INSU-CNRS, CNES and MNHN.

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Correspondence to Marc Chaussidon.

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Chaussidon, M., Robert, F. Lithium nucleosynthesis in the Sun inferred from the solar-wind 7Li/6Li ratio. Nature 402, 270–273 (1999).

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