The exchange of impact ejecta between terrestrial planets

Science

Volumn 271, Issue 5254, 1996, Pages 1387-1392

  Gladman, Brett J ^a   Burns, Joseph A ^a   Duncan, Martin ^b   Lee, Pascal ^a   Levison, Harold F ^c  

^a Department of Population Medicine and Diagnostic Sciences   (United States)

^b QUEEN S UNIVERSITY   (Canada)

^c SOUTHWEST RESEARCH INSTITUTE   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EJECTA; METEORITE FLUX; MICROMETEORITE;

EID: 0029756273     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.271.5254.1387     Document Type: Article

References (47)

1. Named for the three large meteorite falls Shergotty, Nakhla, and Chassigny. H. Y. McSween Jr., Meteorites and Their Parent Planets (Cambridge Univ. Press, Cambridge, 1987).
2. D D Bogard, P. Johnson, L E. Nyquist, Lunar Planet. Sci. XV, 68 (1984)
3. L E Nyquist, J. Geophys. Res. 88, 785 (1983). The SNC meteorites record only very mild shock histories (<1 to 50 GPa), whereas escape from Mars was thought to require >100 GPa, which argued further against their being ejected in a cratenng event A. M Vickery and H. J. Melosh, Icarus 56, 299 (1983)
4. L E Nyquist, J. Geophys. Res. 88, 785 (1983). The SNC meteorites record only very mild shock histories (<1 to 50 GPa), whereas escape from Mars was thought to require >100 GPa, which argued further against their being ejected in a cratenng event A. M Vickery and H. J. Melosh, Icarus 56, 299 (1983)
5. See D. D. Bogard and P. Johnson, Geophys. Res. Lett. 10, 801 (1983) for references.
6. W. A Cassidy and L. A. Rancitelli [Am Sci 70, 156 (1982)] have reviewed Antarctic meteorites, and O. Eugster [Science 245, 1197 (1989)] has focused on some early lunar Antarctic finds
7. W. A Cassidy and L. A. Rancitelli [Am Sci 70, 156 (1982)] have reviewed Antarctic meteorites, and O. Eugster [Science 245, 1197 (1989)] has focused on some early lunar Antarctic finds
8. D. D Bogard and P. Johnson, Science 221, 651 (1983).
9. H Y McSween Jr., Meteoritics 29, 757 (1994). The possibility ol meteorites, like ALH84001, falling outside of the SNC categorization argues further for ceasing to use "SNCs" as a synonym for "martian meteorites." See also D. W. Mittlefehldt, Meteoritics 29, 214 (1994).
10. H Y McSween Jr., Meteoritics 29, 757 (1994). The possibility ol meteorites, like ALH84001, falling outside of the SNC categorization argues further for ceasing to use "SNCs" as a synonym for "martian meteorites." See also D. W. Mittlefehldt, Meteoritics 29, 214 (1994).
11. High-speed, lightly shocked ejecta may be launched by shock wave interference [H. J. Melosh, Icarus 59, 234 (1984)] or by vapor-plume entrainment [J. D. O'Keefe and T. J. Ahrens, Science 234, 346 (1986)]. The cratering physics that launches ejecta at speeds above the escape velocity may differ greatly from the physics of the excavation flow that creates the impact crater
12. High-speed, lightly shocked ejecta may be launched by shock wave interference [H. J. Melosh, Icarus 59, 234 (1984)] or by vapor-plume entrainment [J. D. O'Keefe and T. J. Ahrens, Science 234, 346 (1986)]. The cratering physics that launches ejecta at speeds above the escape velocity may differ greatly from the physics of the excavation flow that creates the impact crater
13. Objects that are shielded by several meters of rock, or even by Earth's atmosphere, do not accumulate radioactivity, and the radioisotopes that are present begin to decay Because of this, with enough measurements of a variety of isotopes, it is possible to calculate (i) the length of time that the object spent in the upper few meters of the parent body before launch (2π age), (ii) the depth at which it was buried, (iii) the duration of its transit to the Earth (4π age), and (iv) the terrestrial age or Earth residence time (t⊕) [R C. Reedy, J. R Arnold, D. Lal, Science 219, 127 (1983)].
14. Paired meteorites are different pieces of the same meteoroid that fragmented during atmospheric entry or was broken apart by subsequent erosional processes. Such pairs should be counted as a single meteorite fall (for example, MAC88104/5 in Table 1). "Source-crater pairing" is also possible, in which two meteorites launched during a single cratering event may travel on independent paths to the Earth, spending different times in space and landing at different locations on the Earth. Nevertheless, CRE and petrologic data may link the two samples as being from the same source crater. It seems unlikely that any lunar meteorites are source-crater paired except for Asuka-881757 and Y-793169 (11) The case is less clear for the martian meteorites
15. P. Warren, Icarus 111, 338 (1994)
16. For details about the lunar simulations, see B. J Gladman, J. A Burns, M Duncan, H Levison, ibid. 118, 302 (1995).
17. H. Lovison and M Duncan, ibid 108, 18 (1994) This integration method is based on the mixed-variable symplectic integrator developed by J. Wisdom and M. Holman [Astron, J. 102, 1528 (1991)]
18. H. Lovison and M Duncan, ibid 108, 18 (1994) This integration method is based on the mixed-variable symplectic integrator developed by J. Wisdom and M. Holman [Astron, J. 102, 1528 (1991)]
19. esc = 4.2, 103, 11.2, and 5.0 km/s, respectively.
20. x is generally much less than the heliocentric orbital velocity of the planet and therefore produces a slightly eccentric and inclined orbit with respect to the planet's orbit.
21. G. W. Wetherill, Meteorites 19, 1 (1984).
22. A. M. Vickery [Geophys. Res. Lett 14, 726 (1987)] studied secondary crater fields around martian, lunar, and mercurian impact craters and found power-law decreases in the fragment size with increasing ejection speed.
23. 1, are the 7th fundamental secular eigen-frequencies of the solar system The resonances are nonlinear because they involve more than one fundamental frequency, and second order because they do not appear in the expansion of the secular disturbing function until quadratic terms in the planetary masses are considered See Ch. Froeschlé and A Morbidelli, in Asteroids, Comets, and Meteors, 1993, A. Milani, M. Di Martino, A. Cellino, Eds. (Kluwer, Boston, 1994), pp. 189-204.
24. Sun-grazing is discussed for near-Earth asteroids by P. Fannella et al. [Nature 371, 314 (1994)], for the short-period comets by M. E. Bailey, J. E Chambers, and G. Hahn [Astron. Astrophys. 257, 315 (1992)], and for the Jupiter-family comets by Levison and Duncan (13).
25. Sun-grazing is discussed for near-Earth asteroids by P. Fannella et al. [Nature 371, 314 (1994)], for the short-period comets by M. E. Bailey, J. E Chambers, and G. Hahn [Astron. Astrophys. 257, 315 (1992)], and for the Jupiter-family comets by Levison and Duncan (13).
26. 1/2 Myr for a meteoroid of radius r (in centimeters) when Q > 2.1 AU. Thus, a meteoroid with r ≃ 3 cm (pre-atmospheric mass, ∼300 g) and aphelion in the main belt would have a collisional lifetime of 2 Myr. In our model, collisional fragments of martian meteoroids arc not large enough to engender recoverable meteorites.
27. N Bhandan et al., Geochim. Cosmochim. Acta 50, 1023 (1988)
28. D D. Bogard, Lunar Planet. Sci. XXVI, 143 (1995). The cumulative spectrum (Fig. 5) is unchanged by source-crater pairings If the interval between martian launches is 2 Myr, then the impactors are ≃1 km in diameter [W. F. Bottke, M. C. Nolan, R. Greenberg, R. A. Kolvoord, in Hazards Due to Comets and Asteroids, T. Gehrels, Ed (Univ. of Arizona Press, Tucson, 1994), pp. 337-358].
29. D D. Bogard, Lunar Planet. Sci. XXVI, 143 (1995). The cumulative spectrum (Fig. 5) is unchanged by source-crater pairings If the interval between martian launches is 2 Myr, then the impactors are ≃1 km in diameter [W. F. Bottke, M. C. Nolan, R. Greenberg, R. A. Kolvoord, in Hazards Due to Comets and Asteroids, T. Gehrels, Ed (Univ. of Arizona Press, Tucson, 1994), pp. 337-358].
30. Treiman and co-workers [A. H. Treiman, J. Geophys Res 100, 5329 (1995), A H. Treiman et al., Meteoritics, 29, 581 (1994)] argue for one-stage exposures as small bodies but allow for source-crater pairing of the shergottites or nahklites-Chassigny An additional constraint that must be satisfied is the puzzling prevalence of martian meteoris from young source terrains This constraint has been used to argue in favor of large martian impact craters [see R A. Kerr, Science 237, 721 (1987)].
31. Treiman and co-workers [A. H. Treiman, J. Geophys Res 100, 5329 (1995), A H. Treiman et al., Meteoritics, 29, 581 (1994)] argue for one-stage exposures as small bodies but allow for source-crater pairing of the shergottites or nahklites-Chassigny An additional constraint that must be satisfied is the puzzling prevalence of martian meteoris from young source terrains This constraint has been used to argue in favor of large martian impact craters [see R A. Kerr, Science 237, 721 (1987)].
32. Treiman and co-workers [A. H. Treiman, J. Geophys Res 100, 5329 (1995), A H. Treiman et al., Meteoritics, 29, 581 (1994)] argue for one-stage exposures as small bodies but allow for source-crater pairing of the shergottites or nahklites-Chassigny An additional constraint that must be satisfied is the puzzling prevalence of martian meteoris from young source terrains This constraint has been used to argue in favor of large martian impact craters [see R A. Kerr, Science 237, 721 (1987)].
33. A. M. Vickery and H. J. Melosh, Science 237,738 (1987).
34. H. J. Melosh and W. B. Tonks, Meteontics 28, 398 (1993)
35. The current formation rate of craters with diameters larger than 10 km is a factor of 2 larger on Mercury than on Mars (although most of the crater-producing projectiles on Mercury are cometary) [G. W. Wetherill, ibid. 24, 15 (1989)]. Mercury's smaller escape velocity should result in a larger meteoroid generation rate. A companson based on the moon's supply (because the present cratering rate for Mercury is at least an order of magnitude larger than the moon's, but the delivery efficiency is 100 times smaller) also yields a few expected mercurian meteorites.
36. J. A. Burns, P. L Lamy, S. Soter, Icarus 40, 1 (1979).
37. S. G. Love and K Keil [Meteoritics 30, 1 (1995)] discuss the Yarkovsky effect and the problems of identifying mercurian meteorites.
38. E Grun, H. A. Zook, H. Fechtig, R. H. Giese, Icarus 62, 244 (1985)
39. The Earth's atmosphere prevents stony objects with diameters <50 m from reaching the ground and creating hypervelocity impact craters [C. Chyba, Nature 363, 701 (1993)]
40. It is conceivable that ejecta could escape out through the atmospheric "tunnel" left by the impactor's entry [H J. Melosh, ibid. 332, 687 (1988)].
41. See C. Koeberl, Annu Rev. Earth Planet Sci. 14, 323 (1986), and references therein.
42. Searches for radionuclides induced by cosmic rays in tektites have produced only upper limits on their time in space, varying from 900 to 90,000 years. Relevant papers are reviewed in J A O'Keefe, Tektrtes and Their Origin (Elsevier, New York, 1976), pp. 160-165. Because the tektites examined were from strewn fields, which implies that they never escaped to heliocentric orbit, these results do not necessanly constrain theories of objects that escape from the Earth
43. Calcalong Creek and QUE93069 have large CRE age uncertainties because of incomplete analyses, we have used the lower ages given in Table 1 in analogy with the other lunar meteorites. Warren (11) argued that the remaining meteorites may be from seven different source craters We accept the proposed source-crater pairing of Asuka-881757 and Y-793169 and go further to assert conventional pairing because the odds of having two lunar meteoroids from the same source crater arrive at the Earth at the same time after spending 1 Myr in space and landing close to each other is so small.
44. T. D. Swindle, M. K. Burkland, J. E. Grier, Meteoritics 30, 584 (1995).
45. K. Nishiizumi, Lunar Planet. Sci. XXVI, 1051 (1995)
46. P. H. Benoit, D. Sears. S. Symes, ibid., in press
47. We thank H. J. Melosh, P. Fannella, P. Warren, and G. Wetherill for constructive input to this study, and three referees for valuable comments. This work was supported in part by National Aeronautics and Space Administration grant NAGW 310.