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The first interstellar object, 1I/2017 U1 (`Oumuamua), exhibited severalunique properties, including an extreme aspect ratio, a lack of typicalcometary volatiles, and a deviation from a Keplerian trajectory. Severalauthors have hypothesized that the non-gravitational acceleration was caused byeither cometary outgassing or radiation pressure. Here, we investigate the spindynamics of `Oumuamua under the action of high surface area fractional activityand radiation pressure. We demonstrate that a series of transient jets thatmigrate across the illuminated surface will not produce a secular increase inthe spin rate. We produce 3D tumbling simulations that approximate the dynamicsof a surface covering jet, and show that the resulting synthetic light curveand periodogram are reasonably consistent with the observations. Moreover, wedemonstrate that radiation pressure also produces a steady spin-state. Whilecarbon monoxide (CO) has been dismissed as a possible accelerant because of itsnon-detection in emission by $\textit{Spitzer}$, we show that outgassing from asurface characterized by a modest covering fraction of CO ice can satisfy thenon-ballistic dynamics for a plausible range of assumed bulk densities andsurface albedos. $\textit{Spitzer}$ upper limits on CO emission are, however,inconsistent with the CO production necessary to provide the acceleration.Nonetheless, an ad hoc but physically plausible explanation is that theactivity level varied greatly during the time that the trajectory wasmonitored. We reproduce the astrometric analysis presented in Micheli et al.(2018), and verify that the non-gravitational acceleration was consistent withstochastic changes in outgassing.

On The Spin Dynamics of Elongated Minor Bodies with Applications to a Possible Solar System Analogue Composition for `Oumuamua