Contents

12 July 1974
Vol 185, Issue 4146

About The Cover

The semicircle of cratered mountains in the left half of this processed photomosaic from the boundary for the largest basin on Mercury seen by mariner 10. The basin is provisionally named ``Caloris'' or ``hot'' basin for its position near one of the subsolar points when Mercury is at perihelion. The ring of mountains is 1300 kilometers in diameter and up to 2 kilometers high; the basin floor consists of intensely fractured and ridged plains. The photomosaic was compiled by personnel at the Jet Propulsion Laboratory and U.S. Geological Survay in Flagstaff. See page 169.