Abstract
Abstract
The recent discovery of the atmosphere around the ∼ 255-km-radius plutino (612533) 2002 XV93 challenges the usual expectation that such a small trans-Neptunian object cannot retain a volatile atmosphere over long timescales. Regarding the observed atmosphere, two possible origins have been suggested: ongoing cryovolcanic activity or a recent impact. We point out that a so far undetected satellite can be the energy source of the cryovolcanism. We derive the relevant tidal heating scaling, the viable satellite parameter space, and outline direct observational tests of the proposed mechanism. For plausible icy-body parameters, 30–100 km diameter companions can sustain such an atmosphere for close, eccentric orbits. The hypothesis predicts a companion directly detectable through high-resolution imaging, rotational light-curve effects, and stellar occultation. Our model also predicts indirect detection possibilities by monitoring the atmospheric evolution via future additional stellar occultation measurements, which also helps to distinguish between impactor and satellite scenarios. Since we estimate the circularization timescale of the hypothetical moon to fall between 10^4 - 10^6 years, we point out that the outer regions of the Solar System still exhibit dynamically intense processes today.