SPINNING OUT OF CONTROL! How Sublimative Torques Alter And Destroy Cometary Bodies

To quote David Levy: “comets are like cats: they have tails, and they do precisely what they want.”  They have strange bilobate nuclei, undergo outbursts (rapid, unpredictable brightening events), and form long  striated dust features in their tails that somehow align with the Sun rather than the nucleus. Additionally, their dynamics appear to require  some mysterious mechanism for reactivating their sublimative activity.  In this talk, I describe how all of these features are a result of the  way that volatile sublimation, the defining cometary process, affects irregularly shaped bodies. Asymmetric sublimative mass loss generates torques that change the rotation state of comet nuclei in a manner analogous to the YORP Effect. Such rotational spin-up can induce internal stresses that fission the nucleus, forming both cometary striae and the strange bilobate shape of 67P/Churyumov-Gerasimenko.

Additionally, I can explain both comet reactivation and the highly collimated outbursts seen at comets as direct results of avalanches triggered by rotation state changes.