  Evidence from the solar system suggests that, unlike Venus and Mars, the
presence of a strong magnetic dipole moment on Earth has helped maintain liquid
water on its surface. Therefore, planetary magnetism could have a significant
effect on the long-term maintenance of atmosphere and liquid water on rocky
exoplanets. We use Olson and Christensen's (2006) model to estimate magnetic
dipole moments of rocky exoplanets with radii R${}_{p}$ $\le$ 1.23 R$_\oplus$.
Even when modelling maximum magnetic dipole moments, only Kepler-186 f has a
magnetic dipole moment larger than the Earth's, while approximately half of
rocky exoplanets detected in the circumstellar habitable zone have a negligible
magnetic dipole moment. This suggests that planetary magnetism is an important
factor when prioritizing observations of potentially habitable planets.
