Caloris Basin
The hilly and lineated unit and the enclosed hummocky plains unit appear to be relatively young; they may be the same age as the Caloris Basin. In addition, they lie almost directly opposite that basin on the planet. Both observations strengthen the suggestion that the hilly and lineated unit and the hummocky plains unit are directly related to the formation of Caloris, possibly through the focusing of seismic waves at the antipodal point.