The dynamics of fluids in the transition zone between light and dark, heat and cold would determine the nature of the planet. Do icy glaciers creep into the sunlight and melt, or do they sublime away to dry dust? Is there a planet-girdloing lake or narrow ocean, with glaciers calving on the polar side and the water steaming away on the sunward side?

Is there enough atmsosphere for winds to blow, or are all the gases locked into a hemispherical ice cap? Mars suggests the latter - with atmospheric pressure of a few millibars at most and a frigid space-pointing pole.

A magnetic field is a very strong possibility because this planet would have more internal heat and hence more convective energy.

However, the coincidence of equatorial velocity disguises the differnce in angular velocity due to different diameter.