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 & Christensen ’ s ( 2006 ) model to estimate magnetic dipole moments of rocky exoplanets with radii R _ { p } \leq 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 .