  Exomoons may play an important role in determining the habitability of worlds
outside of our solar system. They can stabilize conditions, alter the climate
by breaking tidal locking with the parent star, drive tidal heating, and
perhaps even host life themselves. However, the ability of an exoplanet to
sustain an exomoon depends on complex tidal interactions. Motivated by this, we
make use of simplified tidal lag models to follow the evolution of the
separations and orbital and rotational periods in planet, star, and moon
systems. We apply these models to known exoplanet systems to assess the
potential for these exoplanets to host exomoons. We find that there are at
least 36 systems in which an exoplanet in the habitable zone may host an
exomoon for longer than one gigayear. This includes Kepler-1625b, an exoplanet
with an exomoon candidate, which we determine would be able to retain a
Neptune-sized moon for longer than a Hubble time. These results may help
provide potential targets for future observation. In many cases, there remains
considerable uncertainty in the composition of specific exoplanets. We show the
detection (or not) of an exomoon would provide an important constraint on the
planet structure due to differences in their tidal response.
