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Earth and Moon impact flux increased at the end of the Paleozoic

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Science  18 Jan 2019:
Vol. 363, Issue 6424, pp. 253-257
DOI: 10.1126/science.aar4058
  • Fig. 1 Regression of lunar crater age versus 95th percentile rock abundance.

    Updated from (1, 2). Data point labels correspond to dated lunar craters (2) listed in table S1. Rock cover is defined as materials with rocklike thermal inertia and minimum diameters larger than the diurnal thermal skin depth (~0.5 m). This regression differs from previous analysis (2) because of use of an updated rock abundance dataset and an updated age for Aristarchus crater (26), together with a statistical treatment that marginalizes over unacknowledged uncertainties for the published crater ages (3). Red error bars illustrate uncertainties for each crater, and black error bars show the uncertainties implied by the median value of the uncertainty scaling factor c given its posterior PDF (eq. S2). The best fitting parameters in the relation RA95/5 = a × (age/Ma)b are a, 0.33; b, –0.50 (black solid curve); black dashed and dotted curves indicate the 68 and 95% credible intervals. After propagation through the joint terrestrial/lunar Approximate Bayesian Computation rejection (ABCr) analysis (3), the best fitting parameters are a, 0.34; b, –0.51 (cyan solid curve); cyan dashed and dotted curves show the 68 and 95% credible intervals. (Insets) The two-dimensional (2D) distribution of the posterior PDF sample of parameters (a, b) before and after ABCr analysis (black and cyan points, respectively), their marginalized distributions, and p(c), the 1D marginalized posterior PDF of the uncertainty scaling factor c (eq. S2).

  • Fig. 2 Geographic and SFD of rocky lunar craters.

    (A) Geographic distribution of 111 rocky (young) craters with D ≥ 10 km between 80°N and 80°S on the Moon (listed in table S1), scaled by size and color coded according to age. Orange (dark yellow deuteranopia) indicates craters younger than 290 Ma; pink (light blue deuteranopia) indicates craters 290 to 580 Ma old; dark blue indicates craters 580 to 870 Ma old; yellow indicates craters 870 to 1160 Ma old; and white indicates craters older than 1160 Ma. [Background image is from https://astrogeology.usgs.gov/search/map/Moon/LRO/LROC_WAC/Lunar_LRO_LROC-WAC_Mosaic_global_100m_June2013 (27)]. (B) Cumulative SFDs of craters. Red indicates average SFD of craters older than 290 Ma (55 craters; average of cumulative distribution in three age bins: 290 to 580 Ma old; 580 to 870 Ma old; and 870 to 1160 Ma old), black indicates craters younger than 290 Ma (56 craters), and error bars show Poisson noise. The lunar cratering rate has increased by a factor of 2.6 in the past 290 Ma compared with the preceding ~710 Ma.

  • Fig. 3 Age-frequency distributions of lunar and terrestrial craters.

    The lunar crater D ≥ 10 and 20 km curves are shown by the black line, whereas terrestrial craters with D ≥ 20 km (table S2) are shown with the red line. All terrestrial craters are younger than 650 Ma. The lunar impact flux increases by a factor of 2.6 near 290 Ma ago (fig. S1). A simple piecewise model (cyan) demonstrates the break between two rates compared with a simple uniform model (dashed black). The similarity between the lunar and terrestrial distributions suggests that the inferred increase in terrestrial impacts is not a preservation bias.

  • Fig. 4 Positions of terrestrial impact craters and kimberlites in space and time.

    (A) Locations of all impact craters identified in the Planetary and Space Science Centre (PASSC) Earth Impact Database (24), scaled by size and colored by age. Kimberlite occurrences are also shown; solid symbols denote those craters with well-defined ages (n = 624), and white diamonds indicate undated kimberlites (n = 3645) (25). Gray regions correspond to major exposures of Precambrian basement rocks (28), which together with platform areas shown in beige (29) form the stable cratons, where 84% of craters with D ≥ 20 km (and 84.6% of craters with D ≥ 10 km) occur. (B) Chronology of large impacts (>10 km) and well-dated kimberlites for each continent, excluding Antarctica. Colored symbols indicate depth-diagnostic kimberlite zones (labeled and illustrated in the inset). There is an abrupt cut-off in impact crater and kimberlite pipe frequency at ~650 Ma ago, which is coincident with Snowball Earth glaciation during the Cryogenian Period, 720 to 635 Ma ago (1719).

Supplementary Materials

  • Earth and Moon impact flux increased at the end of the Paleozoic

    Sara Mazrouei, Rebecca R. Ghent, William F. Bottke, Alex H. Parker,Thomas M. Gernon

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Supplementary Text
    • Figs. S1 to S6
    • Tables S1 and S2
    • References
    Data File S1

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