Mathematics – Probability
Scientific paper
Oct 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007dps....39.5002b&link_type=abstract
American Astronomical Society, DPS meeting #39, #50.02; Bulletin of the American Astronomical Society, Vol. 39, p.512
Mathematics
Probability
Scientific paper
The terrestrial and lunar cratering rate is often assumed to have been nearly constant over the last 3 Gy. Different lines of evidence, however, suggest the impact flux from kilometer-sized bodies increased by at least a factor of 2 over the last 100 My. Here we report that this apparent surge was triggered by the catastrophic disruption of the Baptistina parent body, a 170 km diameter carbonaceous chondrite-like asteroid that broke up 160 ± 20 My ago in the inner main belt. According to our numerical simulations, this family's age, location near Jupiter's 7:2 and Mars' 5:9 mean motion resonances, and its steep fragment size distribution are remarkably well suited to generate a prolonged surge in the multi-kilometer NEO population and explain the above observations. Numerous fragments produced by the collision were slowly delivered by dynamical processes (Yarkovsky effect, resonances) to orbits where they could strike the terrestrial planets. The number of D > 1 km, D > 5 km, and D > 10 km impacts produced on Earth by Baptistina fragments are 200 ± 60, 6 ± 2, and 1 ± 1, respectively, while those from the background are 260 ± 20, 3 ± 2, and 0.5 ± 0.7, respectively. Using numerical modeling this asteroid shower and combining our results with meteoritic constraints, we find it is the most likely source (> 90% probability) of the Chicxulub impactor that produced the Cretaceous-Tertiary (K/T) mass extinction event 65 My ago. This shower may have also produced the conspicuous lunar crater Tycho that formed 109 My ago (> 70% probability). Among all km-sized NEOs, Baptistina fragments may currently be responsible for 40% of all C/X-types and 20% of the entire population. These bodies should predominantly have compositions that mimic CM meteorites.
Bottke William
Nesvorný David
Vokrouhlicky David
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