Forming Binary Near-Earth Asteroids From Tidal Disruptions

4.2.7 Doublet cratersCurrently any encounter of an asteroid or binary at less than 1 R ⊕ is flagged with theasteroid or binary parameters, allowing investigation of doublet crater formation. Whilethe ratio of doublet to singlet craters would be expected to roughly correspond to the ratioof binary to single asteroids in the NEA population, doublets may still be diagnostic ofthe binary population.For a nominal simulation with 20% binary MBAs, approximately 10% of all craterswere doublet. When the MBA percentage was increased up to 80%, the doublet percentageincreased to 15%. For the second case, about 14% of the impacting binarieshad a semi-major axis greater than ten times the combined radii of their components(a > 10 × R pri + R sec ) roughly approximates the necessary separation needed for an impactingbinary to form two separate identifiable craters). Thus only about 2% of thecraters would likely be detectable as doublets.Tracking ratios of singlet to doublet craters will be significantly more relevant whenthe steady-state population of binaries is at the observed level around 15%. With a cleardeficit of binaries in the NEA population in this steady-state simulation it is not surprisingthat we find such a low percentage of impacts as possibly observable doublets. Currentlyit is estimated that at least 10% (3 of 28) of craters on Earth are doublets (Bottke & Melosh1996a).4.3 ConclusionThis study focused on uncovering how tidal disruption affects the population of NEAbinaries. It is clear from the discussions above that tidal disruption provides only a smallfraction of the observed binary population. We have shown that these binaries appearsimilar to those observed, suggesting that some of these systems were in fact formed via105