Sam Hadden, Yanqin Wu

The spacings of super-Earths in multi-transiting systems exhibit a distribution that is broad and mostly featureless, with the exception of notable excesses of planet pairs situated a few percent wide of first-order mean motion resonances (MMRs). In this work, we extend the so-called "breaking-the-chains" model to account for both of these characteristics. Assuming that super-Earths are settled into stable chains of resonances after disk-driven migration, we show that scattering a planetesimal population that contains only a few percent of a system's mass can reorganize primordial chains in remarkable ways. The planetesimal scattering "rattles" the chains by repelling adjacent planet pairs wide of their initial MMRs. Some chains remain rattled but otherwise intact and make up the observed excesses wide of MMRs. In other systems, however, this initial rattling sows the seeds of later orbital instabilities that break the chains entirely. If individual planetesimals' masses are of order a Pluto mass or so, the onset of these instabilities can occur tens or hundreds of Myr after birth, naturally explaining the apparent disappearance of near-resonant pairs on this timescale. The origin of such Pluto-mass debris is currently unknown.